Harrat Rahat: The Geoheritage Value of the Youngest Long-Lived Volcanic Field in the Kingdom of Saudi Arabia
Harrat Rahat is a volcanic field that consists of over 500 individual volcanoes (Fig. 3.1), many of them with multiple vents forming compound edifices (Camp and Roobol 1989; Coleman and Gregory 1983; El Difrawy et al. 2013; Moufti et al. 2013a). Harrat Rahat was formed over the past 10 million of years (Moufti et al. 2013a), and it is still considered to be an active volcanic region as it has had at least two historic eruptions (Camp et al. 1987; Moufti et al. 2013a). The volcanic field consists of extensive lava fields (Murcia et al. 2014) and various types of volcanic cones and explosion craters (Camp et al. 1991; El Difrawy et al. 2013; Moufti and Hashad 2005; Moufti et al. 2011), each of them is perfectly exposed due to the arid climate and lack of vegetation, and many of them are relatively easy to access (Fig. 3.2). The field is located nearby one of the holiest cities of Islam—Al Madinah—and also hosts the youngest volcanoes in the Kingdom of Saudi Arabia, which have historical and cultural significance (Fig. 3.1). Harrat Al Madinah is the northern part of the Harrat Rahat and the best studied in the Harrat Rahat. The distinction between Harrat Rahat and Harrat Al Madinah is loosely constrained and it has a traditional and geographic connotation rather than geological reasoning. In a similar way, different parts of Harrat Rahat have local names that refer to nearby settlements or other geographical features.
KeywordsLava Flow Explosive Eruption Volcanic Field Lava Dome Scoria Cone
In this chapter we will present a detailed summary of the geoheritage value of the geological features that form the backbone of the geoheritage of Harrat Rahat. The most extensive geoheritage research in Saudi Arabia has been undertaken in the Harrat Al Madinah in the northern part of Harrat Rahat, and that is the basis of a proposal to establish the Harrat Al Madinah Volcanic Geopark. As in other harrats in the Kingdom, the geoheritage research is rather fragmental so far; in subsequent chapters we will provide a brief summary of the geoheritage value associated with other harrats. In describing subsequent harrats we will refer heavily back to the identified geoheritage value of the Harrat Rahat, which will provide a firm scientific basis to justify the high geoheritage value of all the harrats of the Kingdom of Saudi Arabia. The harrats could thus be promoted as a continent-scale world heritage site on the basis of the universal value of observing and studying volcanism.
UNESCO promotes conservation of geological and geomorphological heritage through protection of world heritage sites and development of educational programs under the umbrella of geoparks (Dowling 2011; Farsani et al. 2011; Gordon 2012; Henriques et al. 2011; Joyce 2010). In this chapter we identify significant volcanic features that could be organized and promoted as the first geopark, the Al Madinah Volcanic Geopark in the Kingdom of Saudi Arabia (Moufti and Németh 2013a). The Harrat Al Madinah Volcanic Field has numerous volcanic geosites (Moufti and Németh 2013a b, c) relevant to broadening our understanding of the evolution of volcanic fields dominated by Hawaiian and Strombolian style volcanic cones and lava fields (Kereszturi and Németh 2012a, b).
Harrat Rahat consists of excellent geotopes that illustrate fine details of explosive and effusive volcanism of monogenetic volcanic fields. Thus this is one of the most accessible places on Earth to see the geological context of the birth, evolution and erosion of lava spatter and scoria cone complexes and their associated lava flow fields.
Because Harrat Al Madinah is located so near to Al Madinah city the proposed geopark is easily accessible through highways (and by train in the near future) and it would provide significant economic benefit to Al Madinah city. The park could provide a cost-effective volcanic geoeducation program to pilgrims who are in the city visiting the holy sites.
Through the creation of a world network of natural parks with significant geological features, labelled UNESCO Geoparks, UNESCO promotes conservation of our geological heritage (Dowling 2011; Erfurt-Cooper 2011; Farsani et al. 2011; Joyce 2010). The first step in developing a geopark is to identify geotopes, geosites and geomorphosites which are the key geological features in a region that are easy to access, significant in the global geological sense and that could potentially serve as a basis for broader geoconservation projects (Deraman et al. 2010; Moufti et al. 2013c; Petrovic et al. 2013). Volcanic geoparks are increasingly popular projects worldwide and play a substantial role in geohazard education, including facilitating the dissemination of current research results on the volcanic processes that the ever increasing human society faces (Erfurt-Cooper 2011).
In addition, volcanic geoparks can serve as a geotouristic base that can generate significant economic benefit. Geosites, geomorphosites and geotopes are the smallest “units” of intact geological features that are identifiable through their uniqueness or because they are graphic examples of specific volcanic phenomena or form a vital landscape representative of a specific volcanic processes (Armiero et al. 2011; Erikstad 2013; Fassoulas et al. 2012).
Here we identify significant volcanic features that bear not only regional, but global, volcanic value in a confined area that could be organized and promoted as the first volcanic geopark in the Kingdom of Saudi Arabia: the Al Madinah Volcanic Geopark (Moufti and Németh 2013a). Harrat Al Madinah has many volcanic geosites including the last historically erupted volcanoes in Arabia (Camp and Roobol 1989). Overall, the proposed geopark would provide significant economic benefit to the nearby city of Al Madinah. Pilgrims arrive from every corner of the globe, including countries where volcanic hazard is an everyday aspect of life (e.g. Indonesia); therefore, the proposed geopark would serve as a significant geoeducational hot spot (Moufti and Németh 2013a, b, c).
The recent increased seismic activity in 2009 in the region just north of Harrat Rahat in the Harrat Lunayyir region (Duncan and Al-Amri 2013; Hansen et al. 2013; Mukhopadhyay et al. 2013; Pallister et al. 2010; Zahran et al. 2009; Zobin et al. 2013), also justifies the establishment of an educational site that could play a significant role in the dissemination of scientific knowledge to the public, which could help the population better understand the potential outcome of any volcanic unrest the region may face (Moufti and Németh 2013a; Moufti et al. 2013b, c, d and e).
An historic review of seismic and volcanic events in the Arabian Peninsula, based on English translations of original documents, reveals that an earthquake occurred in 641 AD that destroyed houses in Al-Madinah (Ambraseys et al. 1994). It has been suggested that this earthquake is linked with a volcanic event outside of Harrat Rahat that occurred a year before, in 640 AD (Ambraseys et al. 1994). The location of this event is generally accepted to be a chain of four small cones west of Al-Madinah City (Camp and Roobol 1989), but on further examination the evidence justifying these four cones as the site of the 641 AD eruption is lacking (Moufti et al. 2013b). This volcanic event is associated with one or both of the following eruptions mentioned in historic records and occurred near to Tabuk (about 300 km NW of Al-Madinah City): the Hala’l-‘Ishqa (27.58° N, 36.80° E) and/or Hala’l-Badr (27.25° N–37.20° E) (Ambraseys et al. 1994) in the Harrat Uwayrid (Fig. 3.1). Indeed there are young volcanic landforms located in this region judging from their morphological appearance but their historic age is questionable.
3.2 Volcano Types and the Geoheritage Value of the Harrat Rahat
3.3 Volcanic Precinct Concept and Its Benefits
Geological (and/or geomorphological) sites have just been started to be catalogued in Saudi Arabia with various level of success and/or detail following the geosite (geomorphosites), geotope and geopark concept that has been successfully used elsewhere (Fuertes-Gutierrez and Fernandez-Martinez 2012; Kazancı 2012; Pulido Fernandez et al. 2014; Vujičić et al. 2011). Recently initiated projects in the Kingdom of Saudi Arabia have identified and documented many volcanic geosites that are significant in their context, such as significant in comparison to the host volcanic region where they are located, as well as carrying value that make them internationally important volcanic features to contribute to the global understanding of specific volcanic processes.
Initially an attempt was pursued to establish the first geopark with a volcanic theme near the culturally important region of Al Madinah city (Moufti and Németh 2013a, b and c). An idea to establish a geopark near Al Madinah was argued on the basis of the high scientific, aesthetic and economic potential the volcanic regions near Al Madinah can carry. A proposal is in consideration currently to evaluate the feasibility to go ahead with focused work to establish such geoparks.
Here we provide the geological and geographical scientific information to provide enough background to show that the region is suitable to develop a volcanic geopark. The scientific research recently intensified on understanding dispersed volcanic systems along the western margin of the Arabian Peninsula that brought a new global interest to explore the volcanic fields abundant in this region (El Difrawy et al. 2013; Murcia et al. 2014; Runge et al. 2014; Wahab et al. 2014; Zobin et al. 2013) many of them was triggered by recent seismic unrest likely been caused by dyke intrusions to a very shallow level of the crust (Baer and Hamiel 2010; Duncan and Al-Amri 2013; Koulakov et al. 2014; Mukhopadhyay et al. 2013; Pallister et al. 2010). The fact that Harrat Rahat also host one of the youngest eruption sites (1256 AD) that are exceptionally well-preserved and located nearby Al Madinah city justify clearly that with the abundance of scientific research that can offer a well-designed volcanic geological model a geopark concept can be developed and distinguish these volcanic areas significantly from others on the global scale while can be linked easily to other similar fields elsewhere in the globe along their scientific as well as landscape aesthetic and accessibility value (Moufti and Németh 2013a).
The above outlined logical set naturally offer that in a large area such as any of the harrats in western Saudi Arabia, particularly the Harrat Rahat, the best way to follow some sort of “precinct” concept to link geoheritage sites along their common geoeducational value, and of course their geographical locations (Moufti and Németh 2013a). The “precinct” concept naturally groups together the main and most representative volcanic features (including landforms and associated geotopes) to form at least three distinct precincts as the basis of a proposed volcanic geopark (Moufti and Németh 2013a). The HAMVG’s volcanic landforms naturally offer a three-layered precinct hierarchy with an additional extra level which could be linked to more adventure style geotourism as the site located far from the others and can offer a true remote arid region experience to anyone who would visit those locations, in spite that geologically it is not offering anything significantly different than the other precinct (Fig. 3.16). The precinct concept has been applied to geoeducational programs as the core of a geopark concept in other regions, such as the Kanawinka Geopark in southern Australia and Victoria (http://www.kanawinkageopark.org.au/). In comparison to the Kanawinka Geopark’s precincts, the proposed HAMVG’s precincts are not only thematically but also geographically well-separated, allowing distinct geotourism projects to be designed around them (Moufti and Németh 2013a).
3.4 Volcanic Precincts Versus Volcanic Heritage Routes
Volcanic precinct are favoured against volcanic heritage route design in the case of the Saudi Arabian harrats. Volcanic precincts can offer more than a linear path to explore geoheritage sites along a well-designed route. A precincts can group geosites that are by some reason can be associated with similar geological or geomorphological concept, information or state of research and therefore can be used to target specific audience to visit that sites. In case of the Al Madinah region, the volcanic precincts follow an order that link to the level of adventure tourism needed to explore the grouped geosites with the level of complexity of the volcanological knowledge that could be achieved by a visitor just by completing the specific precinct tours. Near Al Madinah, the 3 + 1 precinct is designed to follow a natural logical path (Fig. 3.16).
Precinct 1 is all about the historic volcanic eruptions that affected the life of the people in the region in the past several centuries, and also had some influence on the cultural development of the region (Fig. 3.16). These sites are easy to access, they are well-preserved, and together they can provide a very good introduction to understanding volcanic processes.
Precinct 2 would involve a little bit longer trip to complete and offers a more detailed understanding of the type of volcanic eruption most common among the harrats, lava spatter cones and extensive lava flows.
Precinct 4 is a more adventurous version of Precinct 3, offered as an alternative for those visitors eager for adventure tourism. The geosites of this precinct are deep inside the interior of Harrat Rahat, and to visit them requires preparation and experience.
Harrat Rahat is appropriate for developing geoeducational and geotouristic projects arranged in precincts rather than in geoheritage routes. Within the precincts, geosites are arranged along routes that link geosites with specific geological value.
3.5 Lava Flow Features and Their Geoheritage Value for Understanding Lava Flow Field Evolution
Harrat Rahat is probably the most accessible harrat in the Kingdom of Saudi Arabia and it is home of a great diversity of lava flow morphotypes (Murcia et al. 2014). The arid climate and the relatively easy access of many of the sites can allow visitors to see most of the lava flow surface textures in their pristine status. The arid climate offers well-preserved lava flow surface textures to be seen. Especially nearby Al Madinah city the extensive road network that are linked to dirt roads across the harrat form an ideal logistic set to select specific lava surface sites to promote and include in various precincts to be listed as key geosites.
The phrase “lava morphotype” refers to the characteristics of the surface morphology of any lava flow after solidification. The lava flow surface morphotypes carry significant information on the cooling history, rheology and the dynamics of the lava flow during its molten stage (Anderson et al. 2012; Duraiswami et al. 2014; Njome et al. 2008; Solana 2012; Suh et al. 2011; Woodcock and Harris 2006). In the Kingdom of Saudi Arabia, young and well-preserved mafic lava fields display a wide range of these morphotypes (Murcia et al. 2014).
Overall, the Harrat Rahat lava flow fields extend up to 23 km from the source, and vary between 1–2 and 12 m in lava flow thickness (Murcia et al. 2014). The lava flow fields cover areas between ~32 and ~61 km2, with individual volumes estimated between ~0.085 and ~0.29 km3 (Murcia et al. 2014). The lava flow surface textures exhibit shelly-, slabby-, and rubbly-pahoehoe, platy-, cauliflower-, and rubbly-a’a, and blocky morphotypes roughly in this order to downflow (Murcia et al. 2014). The specific lava flow surface textures are linked to both intrinsic (i.e. composition, temperature, crystallinity and volatile-content/vesicularity) and extrinsic (i.e. emission mechanism, effusion rate, topography and flow velocity) emplacement parameters and their changes over distances (Murcia et al. 2014). In many places along the 1256 AD lava flow one morphotype transitions to another in individual flow-units or lobes and that they dominate zones (Murcia et al. 2014).
3.6 Volcanic Cones and Their Geoheritage Value
Volcanic cones are abundant in the territory of Harrat Rahat and they range from a very small (~10 m high) to cones that are over 100 m above their surroundings. Cone morphology reflects some degree of their age, and potentially could be used for relative age datings such as it has been suggested and trialled elsewhere (Porter 1972; Settle 1979; Wood 1980a, b). Relative age dating of the volcanic cones based on cone morphometry is, however, in arid climate might not work in a way how early studies predicted as the cone geometry modification is a very slow process and cones can appear in a very youthful appearance after significant time as demonstrated in many scoria cone fields (Kereszturi and Németh 2012a, b).
While the youngest scoria cones are easy to recognize in the field and in satellite imagery, to use their morphometry parameters for relative age dating can be misleading and likely cannot provide high resolution of ages to be able to distinguish even a Pleistocene cone from a Holocene one. An excellent example is the 641 AD four cones just SW of Al Madinah city. The four cones are only inferred to be the eruption sites of the 641 AD historical eruption however their morphology cannot be distinguished from other Pleistocene to Holocene cones. This problem is partially due to the fact that this cones are dominated by lava spatter eruption, similar to many other cones in the Harrat Rahat, that formed collar-like spatter ramparts in their crater rim, that acted as a preventing shield in top of the cones, lowering significantly the erosion speed, and change the style of erosion as predicted in recent studies (Kereszturi and Németh 2012a, b).
3.7 Lava Domes and Explosion Craters as the Results of the Potentially Most Hazardous Volcanism in the Region
The central part of the Harrat Rahat is covered by various silicic (mostly trachytic) pyroclastic deposits forming an extensive ash plain landscape that are surrounded by steep and high lava domes. The lava domes are interestingly commonly associated with older scoria cones and it seems they erupted through pre-existing volcanic landforms. Their composition ranges from mugearite through benmoreite to trachyte (Camp and Roobol 1989).
From the scientific perspective, the common presence of small to medium volume silicic lava domes in a volcanic field suggests that some degree of crustal storage network must exist beneath the Harrat Rahat to form chemically evolved magmas in spite of the general dispersed, volcanic field-forming nature of the volcanism. The relatively small-volume and simple architecture of the lava domes of Harrat Rahat makes them different from those lava domes commonly associated with major central (composite and strato-volcano or caldera) volcanoes such as Merapi, Indonesia (Abdurachman et al. 2000), Unzen, Japan (Fujii and Nakada 1999) or Soufriere Hills in Montserrat (Bourdier and Abdurachman 2001; Carn et al. 2004). The lava domes of Harrat Rahat are single, individual sites that were probably grown over decades, but their eruption was likely controlled by a single or low number of eruptive phases that make them closer relationship with typical monogenetic volcanoes than to those complex and long-lived lava domes commonly developed on top of major long-lived polygenetic volcanoes. In this respect, Harrat Rahat’s lava domes can offer a unique opportunity for scientific research to understand how dispersed lava dome field evolve, and how they contribute to the geological record of volcanic fields.
The silicic lava domes of Harrat Rahat are similar to those lava dome fields documented in association with dispersed small-volume volcanic fields such as those in Central Mexico (Blatter et al. 2001; Guilbaud et al. 2012; Hasenaka 1994; Hasenaka and Carmichael 1985; Riggs and Carrasco-Nunez 2004) or in SW US (Riggs et al. 1997). Similar dispersed lava dome fields have been documented across the Miocene to Pleistocene Carpathian Volcanic Arc (Lexa et al. 2010) that highlight the significance of such small volume lava dome systems in regard to understanding their origin as part of a dispersed volcanic region or volcanic field. In scientific perspective the lava domes of Harrat Rahat are significant features, and can offer key sites to study lava dome formation, their geomorphological evolution and their effect on the surrounding regions through block-and-ash flow eruptions.
In addition to lava domes the Harrat Rahat also host numerous explosion craters (Fig. 3.23). These craters are diverse in their size (crater diameter and depth) and exclusively located in the central part of the field. In the crater wall of these craters commonly half section of older silicic lava domes are exposed indicating some link between lava dome growth and sudden disruption and crater formation. The smallest craters are surrounded by coarse pyroclastic breccias inferred to be explosion breccias. These deposits are rich in accidental lithic fragments and deep crustal origin xenoliths. The juvenile pyroclast content of these pyroclastic rocks are relatively low. The juvenile pyroclasts are low vesicular microlite-rich rocks indicating potential magma-water explosive eruptions as a cause of their fragmentation.
In larger craters such evidence to support potential magma and water explosive interaction is less clear, and the deposits surrounding the craters are more typical block-and-ash flow deposits typical for moderate run-out distance pyroclastic flows. In this respect Harrat Rahat’s explosion craters can be classified as small maar volcanoes to more typical broad craters with even moderate caldera collapse features in their summit. The important aspect of these explosion craters beside the gradual trend from phreatomagmatic to magmatic explosive types of eruption as a driving force to their formation is, that even the largest and most complex craters are relatively simple in comparison to a long-lived silicic volcano. This fact again offer a unique scientific background to establish a scientifically well-established geoeducation program to demonstrate the full spectrum of eruption styles and volcano types associated with a predominantly dispersed, volcanic field building volcanic system such as Harrat Rahat.
3.8 Organisation of Precincts of the Proposed Harrat Al Madinah Volcanic Geopark (HAMVG)
- Precinct 1
Historic Eruption Precinct—1256 AD and 641 AD Historic Eruption Sites;
- Precinct 2
Lava Lakes, Lava Fountains and Volcano Spreading Precinct—The Mosawdah Volcano and
- Precinct 3
From Silicic Lava Domes to Explosion Craters Precinct.
- Precinct 4
An additional Precinct has been outlined as an alternative or extension of the Precinct 3 to provide a stronger adventure touristic aspect to fundamentally the same geological processes Precinct 3 can demonstrate.
Precinct 1 groups volcanic features and associated geoeducational and geotourism programs that demonstrate the eruption sites that have been historically documented and are probably the most relevant to the inhabitants of Al Madinha city. The key to establish this precinct is the direct relevance of the demonstrated volcanic features to the life of the locals. This precinct hosts numerous geosites dealing with extensive transitional pahoehoe-to-aa lava fields with world-class examples of lava flow surface textures, lava spatter and scoria cone (Murcia et al. 2014).
Precinct 2 can be viewed as an expansion of the first, offering the visitor a more in-depth understanding of the type of volcanism very common in the Harrat Al Madinah. Precinct 2 is centered around the main volcanic geotope, the Mosawdah Volcano and its lava flows, and its numerous geosites that provide superb examples to understand the life of a highly active effusive volcano that formed lava fountaining. As a result the volcano under its own erupted hot material gradually collapsed and signs of the edifice spreading and collapse are evident. It is more difficult to access the geosites of Mosawdah volcano than the geosites of Precinct 1 and therefore it would involve some “adventure tourism” style trip which makes this precinct available only to those visitors who wish to go deeper into understanding volcanic processes. Precinct 1 and 2 fundamentally cover the majority of the volcanic features that can be located in the Al Madinah Volcanic Field (Moufti and Németh 2013a).
Precinct 3 offers the most adventurous trips for visitors and some unique additions to understanding the full spectrum of volcanic processes in the AMVF. Precinct 3 volcanic features deal with silica-rich volcanism that formed various lava domes (e.g. trachytic), as well as deep explosion craters, many of them at least in their initial phase were formed due to magma and ground-water explosive interaction. Precinct 3 is located far from Al Madinah city, and only well-equipped geotourists with trained guides can visit the sites. While the volcanic features in Precinct 3 can be seen to have a very high aesthetic and scientific value, they are rather an extra addition to the full picture of the volcanism of the AMVF, than something without which the visitor would get a distorted image of the field. However, those who decide to invest energy to visit Precinct 3 would be well rewarded by a truly dramatic volcanic landscape. Precinct 3 could be expanded toward the south (provisional Precinct 4) as an alternative geoheritage site, where a great variety of pyroclastic flow deposits and associated volcanic craters can be visited. These sites have a very unique landscape value. However, visits to these sites can only be done by well-prepared adventure tours.
3.9 Precinct 1—Historic Volcanic Eruption Sites
The largest historic eruption at 1256-AD that lasted ~52 days produced about minimum 0.29 km3 lava forming a maximum of ~23-km long and 8-m thick flow field (Murcia et al. 2014). This complex semi-confined to unconfined lava field is dominated by transitional flow textures typical for fast moving, open channel lava. Gradual transition from a shelly-, slabby-, and rubbly-pahoehoe, toward platy-, cauliflower-, and rubbly-a’a, reflects lava flow rheology changes (Murcia et al. 2014). The resimulation of the 1256-AD flow with MAGFLOW code (Bilotta et al. 2012; Cappello et al. 2011; Del Negro et al. 2008; Herault et al. 2009) suggests also a complex flow evolution, including late stage ponding of lava around the emission points (Nemeth et al. 2013). Flow inflation/deflation features such as lava rises, tumuli, lava blisters, pressure ridges and evidences of cone rafting are common in proximal areas (Camp et al. 1987; Nemeth et al. 2013). The cones of the 1256-AD eruption are dominated by flattened lava spatter, ash, lapilli with Pelee’s hair and tears, and reticulate suggesting lava fountain-dominated eruptions as well as Strombolian style explosive eruptions (Murcia et al. 2013). Textural features are common for lava lake level fluctuations and lava outbreaks inferred to cause edifice spreading (Nemeth et al. 2013). Other historic eruption took place in 641-AD forming four small cones—recently named as Al-Du’aythah volcanic cones (Murcia et al. 2015)—aligned in NNW–SSE in the western edge of Al-Madinah City (Moufti et al. 2013b). Three out of the four cones has basal phreatomagmatic deposits indicating initial phreatomagmatic explosions (Moufti et al. 2013b; Murcia et al. 2015). This is the only location in the younger (<10,000 years) eruptive centers in the northern Harrat Rahat where evidences of phreatomagmatism are known (Murcia et al. 2015). The 641-AD cones’ upper sequences inferred to be produced by typical lava fountain and moderate Strombolian style explosive eruptions that produced small clastogenic flows reaching less than 300 m from their source (Murcia et al. 2015).
While lava spatter and scoria cones are among the most common volcanic landforms on Earth (Németh 2010; Valentine and Gregg 2008; Vespermann and Schmincke 2000), to see perfectly exposed and unmodified landforms is becoming increasingly difficult because they are either remotely located, have suffered from significant anthropogenic modifications or they are in areas where the vegetation cover inhibits views of the original landscapes. The Precinct 1 “Historic Eruption Precinct—1256 AD and 641 AD Historic Eruption Sites precinct” of the proposed HAMVG comprises volcanic landforms that are well exposed, easy to access and record a unique volcanic process associated with a sustained fissure-fed volcanic eruption, considered to be one of the last major volcanic eruption in the Arabian Peninsula (not counting on those volcanoes erupted recently in the axis of the Red Sea (Xu and Jonsson 2014). Volcanic phenomena represented in this precinct include the results of prolonged lava fountain fed eruptions, such as cone rafting and associated lava lake infill and drain-back, as well as lava flow outbreaks at various points on the fissure-axis edges of the developed volcanic cones. The variety of volcanic features associated with lava fountain type volcanic eruptions is great and ranges from identification of traces of lava-lake level fluctuations in the inner crater walls and clastogenic (rootless) lava flow formation through rapid accumulation of lava spatter in the inner and proximal outer flank of the volcanic cones, to rock records that document fully developed and established volcanic conduit conditions promoted by Strombolian style magmatic gas bubble outburst-driven explosive dispersal of pyroclasts, forming extensive tephra blankets (Hintz and Valentine 2012; Keating et al. 2008; Valentine 2012; Valentine and Gregg 2008; Valentine et al. 2007).
The 1256 AD eruption site with its complex cones along a 2.3 km long fissure form a complete volcanic geotope (Moufti and Németh 2013a; Moufti et al. 2013d and e; Murcia et al. 2013), therefore, it is a significant educational site, where visitors can learn about the complexity of magmatic effusive and explosive eruption styles that may occur along a long lived and evolving fissure, the interaction between effusive and explosive stages of eruptions, as well as the link between changes of eruptive rate and the resulting volcanic landform (and landscape), and the dynamic processes that may take place in volcanic craters. The proximity and easy access to the Precinct 1 “Historic Eruption Precinct—1256 AD and 641 AD Historic Eruption Sites” to the Al Madinah city, coupled with the young age of the eruptions and the historical documentation, make this site the perfect location to provide eye-opening evidence of the style of eruptions the region may face in the future.
3.9.1 Geotope of the 1256 AD Historic Eruption Site and Its Lava Flows
The 1256 AD eruption site is a perfect geotope in the sense of its geological heritage. It is composed of individual volcanic cones erupted in similar style and produced overlapping pyroclastic rock units as well as multiple lava flows. The link between individual geosites are along the fact that they have been produced by similar geological processes slightly differs from each other as the controlling parameters for each eruption was a little bit different. As a result, it is very clear to define the boundary of the geological feature (as the cones along the fissure), easy to link them together along a common geological process (the Hawaiian to Strombolian style eruptions), they are easy to distinguish from other parts of the volcanic field, e.g. they form the volcanic edifices and their proximal areas, that are different geologically then the inter-cone regions where extensive ash plain formed from pyroclastic falls (tephras).
This distinction and separation of these volcanic landforms from others also logical and scientifically valid as they follow the boundary between the volcanic edifice and the surrounding volcanic ring plains and their deposits as it has been outlined in many other areas and many other type of volcanoes (Kereszturi and Németh 2012a, b; Manville et al. 2009; White 1989, 1990, 1991). The 1256 AD eruption site as a geotope offers a great variety of geoeducational sites to be presented. The individual geosites were identified on the basis of their scientific information they can provide, their preservation potential and attractiveness for both professional and general audience.
Pyroclasts that were ejected beyond the 1256 AD cone’s (medial-to-distal pyroclastic succession), forming a tephra cover composed of angular-to-plastically shaped pyroclasts including Pele’s tears, hair and basaltic reticulate (Kawabata et al. 2015; Nemeth et al. 2013). Recent study of the distribution pattern of the ash plain around the cones reviled that the eruptions that produced the pyroclastic fall fed from multiple eruption plumes each representing individual eruption phases (Kawabata et al. 2015). In proximal areas such tephra sections are particularly well-exposed and can offer great geosites to define where visitors can see that even predominantly effusive and mild explosive eruption-dominated volcanoes such as the 1256 AD eruption sites can be associated with extensive tephra fall-producing eruptions. Such researches are recently been conducted in other places on Earth (Németh et al. 2011; Valentine and Gregg 2008; Valentine and Keating 2007; van Otterloo et al. 2013) and therefore the 1256 AD eruption site geotope can be easily linked to those front-line researches and can offer a new aspect to understanding mafic explosive eruption processes and their volcanic hazard aspects.
The complex semi-confined to unconfined lava fields of the 1256 AD eruption are dominated by transitional flow textures typical for fast moving, open channel lava (Bretar et al. 2013; Duraiswami et al. 2003, 2014; Wantim et al. 2011). The gradual transition from a shelly-, slabby-, and rubbly-pahoehoe, toward platy-, cauliflower-, and rubbly-a’a, reflects lava flow rheology changes (Murcia et al. 2014). Flow inflation and deflation features, such as lava rises, tumuli, lava blisters, pressure ridges and evidence of cone rafting, are common in proximal areas. Textural features of solidified lavas in crater settings are common for supporting repeated lava lake level fluctuations and lava outbreaks inferred to cause edifice spreading.
In the following section a summary of individual identified geosites are listed with a short description. The selection was conducted by a scientific evaluation of the sites ranking their scientific importance, uniqueness and their location. While similar features selected and listed below are abundant in the Harrat Rahat, the selected geosites are those that can be easily accessed and/or linked to a broader educational program including the previously introduced precinct concept.
22.214.171.124 Geosite 1—Southern Cone and Hornito Field [24° 20′ 28.37″N; 39° 46′ 39.97″E]
126.96.36.199 Geosite 2—Southern Cone and Lava Tube Field [24° 20′ 37.01″N; 39° 46′ 37.12″E]
188.8.131.52 Geosite 3—Steep Lava Spatter Cones [24° 20′ 42.23″N; 39° 46′ 32.01″E]
184.108.40.206 Geosite 4—Ponded Pahoehoe Proximal Lava Fields and Lava Caves [24° 20′ 48.06″N; 39° 46′ 16.35″E]
In the western side of the main central cone of the 1256 AD eruption side geotope is a proximal area of lava flows erupted from the 1256 AD fissure (Fig. 3.27). This location is one of the most diverse and easy to access in the entire Harrat Rahat in respect of the variety of lava ponding types one can visit in a relatively small area. Its diversity is great in regard of the variety of lava surface textures the visitor can explore as well as the numerous evidences of inflation and deflation of ponded lava flows. The site is an easy walk distance from a sealed road from where with a less than an hour walk the visitor can explore the effect of lava ponding and formation of various features define significant time (days to weeks) when magma was just ponded in the depressions surrounded the growing cones.
The area is best defined as a large silver, grey smooth surfaced region where hummocky surface of the lava flow can be observed (Fig. 3.31). The lava surfaces are smooth with some pahoehoe surface texture marks. Large blocks of smoothed surfaced lava flow fragments are separated by fractures along some dm-scale displacements are common, where the internal texture of the lava crust can be studied. The lava crusts are normally in a dm-scale in their thickness but nearly 1 m thick crusts are also known in the interior of this field indicating that lava ponding must have been taking place over several days or weeks (Holcomb 1981; Polacci and Papale 1997). This observation fits well to the known longetivity of the 1256 AD eruption and this geosite can provide some graphic insight how such historic account could be justified by pure geological observations, which made this geosite an important addition to the geoeducational programs the Harrat Al Madinah Volcanic Geopark could provide.
220.127.116.11 Geosite 5—Pressure Ridges, Flow Channels and Convection Zones [24° 21′ 4.74″N; 39° 45′ 46.32″E]
18.104.22.168 Geosite 6—Reticulite Field [24° 20′ 51.22″N; 39° 46′ 17.88″E]
22.214.171.124 Geosite 7—Cone 3—Pit Crater [24° 20′ 45.82″N; 39° 46′ 30.32″E]
Pit craters form due to sudden withdrawal of magma below a crater through flank eruptions leading to a fast collapse of the crater floor (Carter et al. 2007; Harris 2009; Németh and Cronin 2008). As a result the internal part of the crater wall will be mantled by draping lava and spatter. The outflow points are commonly marked as “boccas” in the outer edifice lower flank. Recognition of pit crater formation bears an important role to establish the eruption mechanism a volcano followed.
The sudden withdrawal of melt likely means that the crater was filled with active lava lakes and that was commonly acted as point source of low lava fountains (Okubo and Martel 1998; Rymer et al. 1998). The 1256 AD eruption site along the 2.3 km-long fissure shows numerous evidences of active lava lake formation then pit crater development. The repeated nature of pit crater formation attests the drainage and refill of magma to a crater. An example provides an ideal geosite to be defined as Cone 3 (Fig. 3.27). This crater is in a short walk from the main access point to the 1256 AD geotope and it provides a perfect view into a twin pit crater. In the inner wall of the crater lava spatters form ramparts and multiple layers of lava lake level markers suggest that the lava lake hosted in this crater changed its level more than once. This geosite has a high educational value to demonstrate that craters can form in a passive way, and explosive activity is not the only way to form a crater (Roche et al. 2001).
126.96.36.199 Geosite 8—Cone 4—Large Scoria Cone with Complex Crater [24° 20′ 52.39″N; 39° 46′ 26.66″E]
188.8.131.52 Geosite 9—Inter-cone Ponded Pahoehoe Lava Field [24° 21′ 2.09″N; 39° 46′ 26.84″E]
184.108.40.206 Geosite 10—Lava Flow Cascade and Lava Flow Termination [24° 21′ 5.04″N; 39° 46′ 31.13″E]
220.127.116.11 Geosite 11—Lava Flow Ponding and Draining Effect [24° 20′ 59.47″N; 39° 46′ 19.87″E]
18.104.22.168 Geosite 12—Cone 5—Bomb-Dominated Cone [24° 21′ 5.21″N; 39° 46′ 21.72″E]
However, cannonball lapilli and bomb with more uniform and smoothed rim and more dense core with entrapped vesicles or older (different textured) lava can be interpreted as recycled colder particle that were ejected subsequently by younger melt from a relatively stable lava lake constantly digested rolled back material and erupted them out through discrete explosions and/or fountain (Alvarado et al. 2011; Bednarz and Schmincke 1990).
The cone flank shows a spectacular view. This geosite can provide information to the visitor that active lava lakes must have existed in this crater, where recurrent bubble coalescence exploded the degassed magma that then formed cannonball-like fragments. This is a more calm explosive processes in comparison to those where reticulate formed and therefore this geosite can provide a reference to two end-member style of explosivity a future eruption would likely cause in the Harrat Rahat. The crater of the cone is also well-exposed and provides further evidences for pit crater formation and crater floor subsidence by drainage of the lava lake.
22.214.171.124 Geosite 13—Cone 6–7—Main Cone [24° 21′ 17.45″N; 39° 46′ 18.82″E]
126.96.36.199 Geosite 14—Collapsing Cone Zone [24° 21′ 15.61″N; 39° 46′ 16.78″E]
188.8.131.52 Geosite 15—Lava Flow Field Slope Angle Changes, Flow Transitions [24° 22′ 30.41″N; 39° 46′ 5.46″E]
In proximal areas it has been demonstrated clearly in a relatively small-scale (hundreds of metres) that lava ponding and sudden break outs from the ponded zones can form transitional lava flow morphotypes. In more distal areas in the main artery of the 1256 AD 23 km-long lava flow there are very graphic examples to explore this phenomena in large scale. This geosite is one of the best examples to demonstrate that lava ponding can take place en-route along the main long lava flows, especially when morphology barriers or depressions are common. This geosite shows such ponded lava zones, that then quickly cascaded through an about 20 m drop in the topography, leading to form a channelized rubbly pahoehoe texture to develop on the fast moving lava flow. This geosite has an important role to demonstrate to the visitors that lava behaves very differently in comparison to water, and unexpected inflational events and ponding can occur frequently. When such ponded zones break out, fast moving transitional type lava flows tend to form. Thus this geosite provides a fine example of the paheohoe to aa lava flow transition as strongly controlled by the viscosity of the melt due to cooling and the slope angle on the flow move (Duraiswami et al. 2003; Kilburn 1981; Peterson and Tilling 1980; Rowland and Walker 1990).
184.108.40.206 Geosite 16—Lava Flow Squeeze Outs in Distal Areas [24° 26′ 23.07″N; 39° 46′ 17.45″E]
The above listed geosites of the 1256 AD Al Madinah eruption are best to visit by following three suggested study paths (Fig. 4.44). There are three levels of study paths recommended to be developed. Two of them can be done by walking off from a general starting or access points, while the third one offer an introductory dirt road experience that follows a full circle around the 1256 AD cones and the medial part of the main lava flows of the eruption.
Northern Circuit Walking Path
Southern Circuit Walking Path
Cone and Lava Field Car Route
The Cone and Lava field car route (Fig. 3.44) follows dirt roads that completely circle the 1256 AD eruption’s 7 cones and their proximal to medial lava flow fields. This trip can be offered to visitors who are not interested in exploring the proximal areas by foot, and/or have limited time. This trip can provide multiple vantage points to the main cones of the 1256 AD eruption. En-route the circle provides short stop options to examine specific geosites, especially those associated with the lava flow surface textures. This study path also recommended as a test trip to those wish to explore the Harrat Rahat in its more remote geosites in the Precinct 2, 3 and 4.
3.9.2 Geotope of the 641 AD Historic Eruption Site
The four cones have young volcanic morphology, such as steep cone flanks, near angles of repose slope, intact crater rims, and limited gully formation on its outer flank, all of which is suggestive of young eruption ages, when their geomorphology features are compared to other young cones elsewhere (Murcia et al. 2015). Each of the four cones is similar in size, with a base diameter of about 200–250 m and relative heights of about 30–50 m. The tallest, but simplest, volcano is the most southern and is composed of a conical shaped edifice with an enclosed single crater. The other three cones are somewhat more complex and exhibit multiple craters and complex volcanic stratigraphy, ranging from a basal tuff ring abundant in accidental lithic fragments commonly cored in lapilli and bombs to various types of scoria cones, lava spatter cones, small lava coulee and short lava flows. The upper sequences of the cones are inferred to be produced by typical lava fountain and moderate Strombolian style explosive eruptions that also initiated small clastogenic lava flows reaching less than 300 m from their source.
The thickest tuff ring sequence has been recorded as a 5 m thick succession of lapilli tuff that is inferred to have been formed by an initial explosive eruption triggered by the interaction of rising basaltic magma and the shallow ground-water table, and the resulting pyroclastic rocks are defined as a basal phreatomagmatic succession. While phreatomagmatism is inferred to be the cause of the initial explosive, vent opening stage in many older (0.3–0.7 Ma old) volcanoes of the Harrat Rahat (Moufti and Németh 2013a), such records in association with small basaltic volcanoes are not known in the vicinity of Al-Madinah City, especially not in other young or historic eruption sites.
The 641 AD volcanic geotope can host several individual geosites that are each can be used as a standalone geoeducational location to promote several aspects of mafic explosive and effusive volcanism. The proximity of the location to Al Madinah city, the site relatively small size and the complexity of volcanic features well preserved and exposed make this geotope a unique location future geoeducation programs could use, and as proposed could be the gateway to the great Al Madinah Volcanic Geopark (Moufti et al. 2013b). This geotope also contains the majority of the volcanic features the visitor can come across by visiting the greater Harrat Rahat region, and therefore it can be used as a jump-desk to develop any further geoeducational programs to a remote and fairly large region of Harrat Rahat.
220.127.116.11 Geosite—Cone 1—Intact Scoria Cone [24° 24′ 33.44″N; 39° 29′ 56.10″E]
18.104.22.168 Geosite—Cone 2—Thin Veneer of Phreatomagmatic Base and Spatter-Covered Crater Interior (S3–4) [24° 24′ 42.18″N; 39° 29′ 51.17″E]
22.214.171.124 Geosite—Cone 3—Scoria Section (S1–1) [24° 24′ 49.63″N; 39° 29′ 48.40″E]
126.96.36.199 Geosite—Cone 3—Lava Dome (S1–2) [24° 24′ 51.50″N; 39° 29′ 49.08″E]
The top of the Cone 3 is covered by a lava dome and spine that fed a very short blocky lava flow. The lava flow is rather a lava dome that uplifted the internal part of the scoria cone and partially protruded through the edifice sliding fragments. This location provides a good example that volcano destabilisation and collapse can take place in such small volcanoes and they can pose a syn-eruptive hazard. This geosite also provides a good introduction to an intra-crater intrusive process that can be explored in large scale in the remote parts of the Harrat Rahat.
188.8.131.52 Geosite—Cone 3—Exposed Phreatomagmatic Base (S3–2) [24° 24′ 48.03″N; 39° 29′ 45.25″E]
The base of the Cone 3 is composed of about 4 m thick exposed lapilli tuff and tuff that is bedded, well-bedded to cross-bedded and contains abundant country rock fragments. Many of the country rock fragments are partially or fully covered by thin lava coat, indicating a low viscosity melt that entrapped them. The cored bombs are inferred to have been derived from the alluvial fan filling a basin nearby the bounding Precambrian horsts. The phreatomagmatic base is the thickest at the Cone 3 suggesting that the initial phase might have been short, but it has been excavated significant portion of country rocks that ended up in the accumulating basal pyroclastic succession.
This geosite bears with a very significant educational value to be able to show the differences of the pyroclastic succession formed due to explosive magma and water interaction. As phreatomagmatic successions are rare in the Harrat Rahat, the presence of them in relationship with the small cones of the 641 AD eruption site can keep the public attention on the fact that in low-land and in more humid periods, phreatomagmatism can take place in an otherwise arid region. This fundamental volcanic hazard aspect cannot be underestimated.
184.108.40.206 Geosite—Cone 3—Exposed Transition Between Phreatomagmatic Base to Scoria Deposits (S3–3) [24° 24′ 47.41″N; 39° 29′ 47.58″E]
A transitional section in the southern flank of the Cone 3 can provide another unique geosite where the visitor can explore how continuous the transition between the phreatomagmatic and magmatic eruption driven pyroclastic succession. This indicates that the eruption were likely continuous (e.g. no break) and the eruption style must have changed during the evolution and growth of the cone. This geosite therefore can convey important messages such as (1) initial phreatomagmatic explosive eruptions can change to be more magmatic gas-driven if the water supply drops or vanishes in the course of the eruption and (2) if the magma eruption rate is large enough, the initial phreatomagmatic pyroclastic successions can be completely covered by a large scoria cone. This later message is important as other scoria cones, especially in the Al Madinah basin where ground water is available, might have had the similar thin phreatomagmatic base.
220.127.116.11 Geosite—Cone 4—Exposed Phreatomagmatic Base (S3–1) [24° 24′ 52.48″N; 39° 29′ 40.59″E]
Cone 4 is the most northerly cone of the four 641 AD cones (Fig. 3.48). The base of this cone similar to Cone 3 and this geosite demonstrate similar features but in different volcanoes as the previous geosite. The significance to of this geosite is that such thin phreatomagmatic veneers can form very irregular base of this cones that can be partially or entirely covered by subsequent eruptive products. Probably the Cone 3 and 4 are those cones where the magma eruption volume and rate were too small and the basal phreatomagmatic pyroclastic unit were not covered completely, and therefore we still can see that initial phreatomagmatic explosive eruption took place.
18.104.22.168 Geosite—Cone 4—Short Lava Flow Terminus (S2–1) [24° 25′ 1.91″N; 39° 29′ 40.92″E]
22.214.171.124 Geosite—Cone 4—Partially Collapsed Cone (S2–2) [24° 24′ 58.58″N; 39° 29′ 44.21″E]
The top of the Cone 4 is composed of a double crater. It seems that an initial crater has been truncated by the outpouring lava flow that partially rafter the flank of the cone away. As a result, the surface of the lava flow is littered by cone flank remnants and large pyroclasts such as fluidal bombs and blocks. This geosite therefore is important to demonstrate that the crater of a volcano is an active playground where gravitational collapse, rafting by outpouring of lava flows and explosive eruptions can act and shape it to their final form. This is again and important aspect to introduce in this geosites, because similar processes but in larger scale are very common across the Harrat Rahat, and therefore this geosite can be used as a starting point for such geoeducational programs.
126.96.36.199 Geosite—Cone 4—Crater of Cone 4 (S2–3) [24° 24′ 55.74″N; 39° 29′ 45.47″E]
The Cone 4 has a well-developed crater from where the visitor can have a nice view toward the short lava flow. From this point as a geosite the visitor can get an insight to the dynamic processes of how volcanic craters evolve.
Walking Path 1
Walking path 1 is the shortest and easiest walking path exploring the Cone 4 (Fig. 3.55). The main goal of this study path to provide a first-hand easy experience to the visitor to see the conditions of a lava field, cone flank and the potential features they can come across in the harrats.
Walking Path 2
Walking path 2 requires a little bit better physical conditions from the visitor as it explores the Cone 3 (Fig. 3.55). It takes the visitor up to its summit and it also provides a good way to connect the basalt phreatomagmatic successions to the capping magmatic explosive and effusive units. From the top of the Cone 3 a perfect view can be enjoyed toward Al Madinah city. This walking path can emphasize the volcanic hazard aspect of the proposed geopark as the visitor will see clearly how much the city expanded since the 641 AD eruption, and today its outskirts are located in the harrat.
Walking Path 3
Walking path 3 takes the visitor around the Cone 3 (Fig. 3.55). Instead of walking up to the cone, the visitor can stay in level and just complete a circle to see the phreatomagmatic successions and the overview of the complex scoria cone that is capped by a lava spine.
For an easy overview, a driving tour can be arranged that takes the visitor around the four cones allowing stops at key geosites focussing on the basal phreatomagmatic succession (Fig. 3.55). The car tour option also can provide opportunity for families to stop by and explore the volcanic features with good options for picnicking.
3.9.3 Scoria Cone with Ottoman Fortress Geotope [24° 20′ 17.47″N; 39° 35′ 13.14″E]
188.8.131.52 Geosite—Cone Base
The base of the complex cone demonstrates a fine example to examine the erosional processes of a scoria cone. The thick reworked scoria fan resulted from the gradual erosion of the cone itself, and its base now covered by modified grain flow-dominated volcaniclastic sediments. The way up to the cone follows the gradual transition from the reworked part of the cone to the more primary volcanic explosive eruption dominated scoria and bomb beds in the top of the cone. The geoeducational value of this geosite is based on its good exposure and graphic examples, that the scoria cone edifices’ base are dominated by volcaniclastic deposits that were formed due to the mass movement on the flank of the cones.
184.108.40.206 Geosite—Cone’s Double Crater and Fortress
3.9.4 Al Madinah Water Management Geotope
220.127.116.11 Geosite—Water Dam 1 [24° 26′ 34.15″N; 39° 55′ 8.38″E]
18.104.22.168 Geosite—Water Dam 2 [24° 26′ 28.80″N; 39° 55′ 2.74″E]
A second major water dam show a smaller construct with lower but wider dam. The presence of this dam highlight the fact that in early time water management was fairly advanced in the region and surface water availability was great enough to invest to build such complex structures. This also indicates that especially in humid conditions, the potential to have phreatomagmatic explosive eruptions in the future if new vents would be opened in this region cannot be excluded.
3.10 Precinct 2—Collapsing Cones, Lava Spatters and Lava Flows
The volcano has been assigned to be ~0.6 Ma and 4500 BP in age (Camp and Roobol 1989), based on relative stratigraphy relationships with nearby volcanic landforms. At least three concentric nested crater rims can be identified around the main pit crater (Fig. 3.62). Each crater rim has a steep, near-perpendicular crater wall and relatively flat outward dipping outer rim. The entire volcano appears as a large (about 700 m wide) nested volcanic landform with multiple craters. Mosawdah volcano shows some similarities to the 1256 AD nested volcanic cones and logically can be connected to the geoeducational programs developed for the 1256 AD cones as part of the Precinct 1 of the proposed Al Madinah Volcanic Geopark. Mosawdah volcano however can provide a much more graphic example of an eruption that produced fast-moving, large-volume lava flows, high eruption rate driven lava fountaining and a complete rheomorphism of the accumulated pyroclasts along the active vents, similar to those that have been described during the Izu Oshima eruption in Japan in 1986 (Sumner 1998; Sumner et al. 2005). The Mosawdah volcano is open toward the northwest, from where a ~10 km long lava flow initiated toward the SW at about the same elevation from the outside flank of the cone as the base of the central pit crater.
The lava flows are relatively thin (few metres) tube fed pahoehoe flows and channelized a’a lavas that spread broadly across the low lying areas around the cone. The lava fields are clearly visible from the top of this geotope and provide a spectacular view of a lava flow field that partially engulfs the central cone, leading to its gradual spreading and rafting. The main volcanic cone is about ~0.6 km in diameter at the base, with a maximum height of ~50 m, suggesting some sort of gradual spreading of the cone on top of a hot and fluid lava base.
Large lava spatter cones are common volcanic landforms associated with extensive low viscosity basaltic eruptions on intra-continental to ocean island settings (Kereszturi and Németh 2012a, b). There are numerous, well described examples of active lava spatter cone formation from Hawaii (Lefevre et al. 1991; Parfitt and Wilson 1995, 1999; Parfitt et al. 1995) or Iceland (Ilyinskaya et al. 2012). Lava spatter cone remnants are common volcanic landforms among many of the Miocene to Pleistocene European or western US intra-continental volcanic fields (Carracedo Sanchez et al. 2014; Valentine et al. 2000); however, they are commonly heavily vegetated and only sporadic outcrops of preserved rocks are visible. The Mosawdah volcano offers a perfectly exposed, non-vegetated, large volume example of the result of lava spatter eruptions. Mosawdah volcano also has a regional significance in terms of understanding the full spectrum of volcanic processes in the Harrat Al Madinah. The volcanism that created the Mosawdah volcano represents an end-member of the eruptive style spectrum, characterized by continuous and prolonged activity of relatively low lava fountains that provided fast accumulation of lava spatter around the active vent(s), promoting the formation of localized agglutinate and clastogenic lava flows.
The high heat source and the fast accumulation rate of lava spatter, in concert with a stable lava lake in the center of the volcano, created a ductile, partially molten base of the volcano, promoting gradual spreading and repeated lava lake drain-back and infill associated with extensive lava flow outbreaks. In this respect, the Mosawdah volcano is probably the best exposed and easiest to access site in the Harrat Rahat to provide an insight into the active lava fountain and lava lake driven eruption style that was common in the eruptive history of many of its volcanoes. Therefore, Mosawdah volcano and the proposed precinct around it bear significant geoeducational value to demonstrate the highly effusive, moderately explosive style of volcanism the region has experienced in the past and could experience in the future.
3.10.1 Mosawdah Volcano Geotope
22.214.171.124 Geosite—Pit Crater, Lava Outflow and Spatter Rampart [24° 14′ 13.80″N; 39° 47′ 48.37″E]
126.96.36.199 Geosite—Collapsing and Spreading Section of Cone [24° 14′ 12.73″N; 39° 47′ 53.48″E]
3.10.2 Al Anahi Volcano Geotope [24° 15′ 34.03″N; 39° 47′ 18.51″E]
Just north from the Mosawdah volcano, a remote scoria cone form a remarkable landform. The Al Anahi cone is a large scoria cone with complex crater and an extensive lava flow, all showing young morphological stages. The Al Anahi volcano can be defined as an intact geotope and can form an alternative site to visit for those wish to have adventure style geotourism.
188.8.131.52 Geosite—Al Anahi Cone [24° 15′ 34.03″N; 39° 47′ 18.51″E]
184.108.40.206 Geosite—Al Anahi Flow Field [24° 14′ 51.53″N; 39° 45′ 3.01″E]
The lava flow of Al Anahi is defined as a geosite where the visitor can explore a thick and long lava flows with aa-type lava flow surface textures. The Al Anahi lava flow is one of the best examples in the Harrat Rahat to show typical aa lava surface textures. The lava flow is steep walled, contain abundant rugged lava spines, collapsed blocks and have milled cauliflower textures all indicative to more viscous lava to be emplaced. The flow itself acts as a major barrier to cross the harrat, and visits to this geosites are only recommended along its margins. In the marginal areas this lava flows show lots of evidences of late stage squeeze outs and collapse of the lava fronts exposing sheared conchoidal shape lava surfaces with pressure ridges. This geosite has a high educational value to demonstrate the lava morphology type varieties the lava viscosity can create, and also provide graphic example to demonstrate the volcanic hazard caused by a fundamentally aa-type lava emplacement.
3.10.3 Fissure Vent and Five Fingers Flow Field Geotope
220.127.116.11 Geosite—Fissure [24° 15′ 41.63″N; 39° 51′ 34.99″E]
18.104.22.168 Geosite—Southern Fissure Cones [24° 17′ 52.80″N; 39° 50′ 59.83″E]
22.214.171.124 Geosite—Northern Fissure Cones [24° 20′ 49.16″N; 39° 49′ 56.73″E]
The northern sector of the fissure aligned vent system in the Northern Harrat Rahat is the apparent source of the northern two arms of the five fingers lava flow (Murcia et al. 2014). In this location older cones form an obstacle for the outpouring of the lava however some remains of the original lava spatter cones can be recognized alongside with a great variety of collapsed pits and lava tube roofs. This geosite has a geoeducational value because it shows clearly that the rejuvenation of volcanic activity in a same place can form amalgamated volcanic landforms that overlap each other. The interaction of the vents emitted the lava flows with older cones aligned to the same direction than the fissure suggests that the region was common area where volcanic eruptions took place. This site therefore can contribute significantly to our understanding of the volcanic hazard aspect of a long-lived volcanic field.
126.96.36.199 Geosite—Five Fingers Lava Flow Field Proximal Section—South [24° 20′ 49.16″N; 39° 49′ 56.73″E]
188.8.131.52 Geosite—Five Fingers Lava Flow Field Proximal Section—North [24° 21′ 12.61″N; 39° 49′ 14.15″E]
184.108.40.206 Geosite—Five Fingers Lava Flow Field Median Section [24° 24′ 56.11″N; 39° 50′ 56.18″E]
220.127.116.11 Geosite—Five Fingers Lava Flow Terminus [24° 23′ 42.79″N; 39° 59′ 18.36″E]
18.104.22.168 Geosite—Five Fingers Lava Flow Field’s Rafted Cone Material and Northern Flow Terminus [24° 26′ 42.78″N; 39° 50′ 23.48″E]
3.10.4 Zargat Abu Zaid Geotope [24° 16′ 32.83″N; 39° 50′ 25.16″E]
Zargat Abu Zaid is a large scoria cone just west of the fissures fed five fingers lava fields. The cone is very likely an older cone as its flank has extensive gully network in spite of its steep cone flank. The crater rim is well-preserved as a collar-like feature as a result of the preservation of softer scoria beds capped by lava spatter banks. This scoria cone is a perfect example to demonstrate the syn-eruptive eruption style influences on the volcanic facies architecture that then controls the post-eruptive erosion style of the cone (Kereszturi and Németh 2012a, b). The scoria cone also has an extensive lava field that partially rafter away its northern sector that have been partially rebuilt by the ongoing eruption. This scoria cone with its lava field can demonstrate the cone rafting processes that took place in a time when the cone was still erupting and producing ash and lapilli that then partially covered the moving lava flow. The cone with its lava field together is a geotope due to the intact geological features they can demonstrate.
22.214.171.124 Geosite—Crater Infill [24° 16′ 30.02″N; 39° 50′ 17.88″E]
126.96.36.199 Geosite—Rafted and Ash-Covered Flow Field
3.10.5 As-Sahab Geotope [24° 21′ 16.42″N; 39° 48′ 48.00″E]
188.8.131.52 Geosite—Cone Complex
The As-Sahab scoria cone is a large cone in its advanced erosion stage (Fig. 3.78). The cone southern side is open and the cone has been eroded and lowered significantly. The geosite can be accessed by foot through the southern open crater. In the interior of the crater the inner crater wall is filled with lava spatters forming hanging lava drapes on the agglutinated steeply crater-ward dipping beds. Large clastogenic lava zones can be seen from below, however, access to those sites and in general to the crater rim’s higher part is not advisable due to high potential for rock falls. The crater internal part is partially filled with volcaniclastic deposits mixed with aeolian dust. In spite of the infilling, the crater is still forming a shallow depression suggesting that its original depth and geometry must have been dramatic, and likely hosted a lava lake that have been drained laterally by “boccas” feeding the older lava flow fields located in this area. The significance of this geosite is that it can show a link between young and older volcanic landforms and demonstrate clearly that similar volcanic processes must have taken place over thousands and thousands of years. This geosite also provides a good example to compare the older and younger volcanic landforms.
184.108.40.206 Geosite—Interaction Between Fissure Flow and Cone
Jabal Al Malsa cone northern and eastern sector is partially covered by the five finger fissure-fed lava field (Fig. 3.78). Previously the cone was under debate as a potential main source of the fissure fed young Quaternary lava flows nearby. Recent fieldworks however suggest that Jabal Al Malsa is an older cone due to its morphological appearance. Along the contact between the young fissure-fed lava flows and the cone it is perfectly visible how an obstacle can divert and interact with a pahoehoe to aa transitional lava flow field. Along this contact zone the visitor can see complex lava surface textures while in the distant regions the proximal lava flow fields show a stunning volcanic landscape with open channels, pressure ridges, inflation features, tumuli and large rotate blocks of ripped up lava crusts. The geosite geoeducational value is high as it is also provide a very good vantage point to demonstrate that the older scoria cones in the region are also aligned to the same fissure orientation along the younger extensive lava flows were emitted.
3.10.6 Halat Khamisah Scoria Cone and Lava Flow Field Geotope [23° 55′ 25.18″N; 39° 54′ 38.53″E]
220.127.116.11 Geosite—Ash Plain [23° 55′ 39.00″N; 39° 54′ 48.01″E]
The Halat Khamisah scoria cone forms a fairly large scoria cone that has steep cone flank indicating its young age. The edifice is covered by dark (black) scoria ash and lapilli that is littered by well-developed spindle bombs especially in the proximity of the cone. Where the cone slope angle reduced, black ash plain can be traced over few kilometres away from the cone foothill. This ash plain is exposed in cross-sectional view in few wadis about a km away from the cone, providing unique window to the internal texture, thickness and vertical variations of a scoriaceous ash and lapilli succession. The ash plain as a geosite beside its aesthetic value provides an important insight to understand the explosive eruptions associated with the cone building. The extensive nature of the ash plain suggests that at least in few stages, the eruption of the Pipeline cone might have been more violent than a normal Strombolian style explosive eruption, and it has been able to produce large volume of finer grained pyroclasts that were dispersed across the landscape as documented elsewhere (Kawabata et al. 2015; Németh et al. 2011; Pioli et al. 2008; Rowland et al. 2009). This geosite has a great geoeducation value as it demonstrates that in Harrat Rahat violent Strombolian style eruptions took place and we have every reason to assume that such eruptions might take place in the future.
18.104.22.168 Geosite—Cone Crater [23° 55′ 11.93″N; 39° 54′ 28.45″E]
The Pipeline cone crater can be accessed relatively easily from the cone southern foothill. The walking path to the crater is a gentle ascending path going through various lithofacies of the edifice building pyroclastic units. There are large spindle bomb-rich parts and fine grained more scoriaceous lapilli- and ash-dominated successions suggesting that the eruption style of this cone through its growth has changed many times. The crater of the cone is partially open toward the west and it is occupied by an outflow of a major blocky—aa lava. In the breaching point of the lava flow the cone flank is destroyed and displaced by rafting, however rafter materials cannot be traced long from the breach point suggesting that the crater rim might have been originally low in the west. The proximal zone of the lava filling the crater is typical aa lava with spines, large lava columns and lifted and rotated angular, crystalline lava blocks (Robert et al. 2014; Wantim et al. 2011). This geosite has a reasonable geoeducational value as this is among those rare sites where typical aa and block lava is exposed from their proximal section. Pahoehoe lava surface types are rare in this lava flow field.
22.214.171.124 Geosite—Block Lava Flow Field [23° 54′ 58.21″N; 39° 53′ 3.59″E]
This geosite refers to a lava flow cross sectional point about 3 km from the crater down-flow. Going up to the crater and follow the lava flow down is a very challenging track and it is not advised as the danger of injury is high due to the numerous steep and deep fissures between lava blocks. In this geosite however it is clearly visible how a typical aa-lava looks like. The lava is composed large blocks, and in places it closely resembles block lavas rather than aa. The lava flow interior has numerous large rounded cauliflower type lava balls, and vertically oriented spines as typical features of aa lavas. This geosite geoeducational value s to demonstrate that a seemingly block-dominated lava that is generated from a higher viscosity melt (more crystalline for instance) can produce lava flows that can travel over 10 km from their source even in a relatively flat surface.
3.11 Precinct 3—From Silicic Lava Domes to Explosion Craters
Explosive volcanic processes are typically the most hazardous aspect of volcanism to human life and associated built environments of the modern society. Explosive volcanism registers on a broad scale from weak to highly explosive eruption styles.
The Precinct 3 at the proposed Harrat Al Madinah Volcanic Geopark named as “From Silicic Lava Domes to Explosion Craters precinct” offers a very dramatic insight for the visitors into the eruptive products that result from various types of explosive volcanism from different magma compositions (Fig. 3.16).
Explosive volcanism associated with monogenetic intra-continental volcanic fields is typically caused by magmatic gas expansion of volatile-rich magmas, commonly more silicic in composition, and/or by magma-water interaction, causing phreatomagmatic explosions that form base-surges and other pyroclastic density currents and construct maars and tuff rings (Valentine and Gregg 2008). The central part of Harrat Al Madinah contains the best closely spaced examples to see the results of explosive volcanism in the form of extensive pyroclastic density current deposits and broad and deep explosion craters (Camp and Roobol 1989). These violent types of volcanism are inferred to be several hundreds of thousands of years old (Camp and Roobol 1989), seemingly forming a concentration of specific volcano types in a remote but accessible region of the proposed volcanic geopark. As it is the furthest precinct from Al Madinah city, as well as it contains some of the oldest volcanism in the Harrah Al Madinah, it is logical to offer this precinct as the last for the visitor. The logistical difficulties in visiting this precinct also make this location suitable for the more adventurous tourist with higher levels of fitness (Moufti and Németh 2013a). However, visitors to the precinct will be rewarded with probably the most dramatic, and one of the most unique, volcanic landscapes anywhere on Earth.
As is typical of arid areas with limited ground and surface water availability, the Al Madinah Volcanic Field has dominantly produced scoria cones, spatter cones and large lava flows, all derived from “dry” magmatic eruptions as presented in the previous two precincts (Moufti and Németh 2013a). However climate changes over the lifespan of a volcanic field (millions of years) can dramatically change the hydrology and hydrogeology of the region, and an otherwise “dry” eruption style-dominated field can quickly can be switched to a “wet” eruption dominated system, even without requiring dramatic magmatic composition changes (Kereszturi et al. 2011). As a result such volcanic fields can produce phreatomagmatic volcanoes such as maars and tuff rings.
Beside the dramatic volcanic landscapes of the explosion craters, the Precinct 3 includes truly unique volcanic landforms that record silicic lava dome formation and associated features. It is an interesting aspect of the Harrat Al Madinah’s volcanism, which has global significance, that silicic (mostly trachytic) lava domes have been produced in the same region where basaltic scoria and lava spatter cone forming eruptions were dominant (Moufti and Németh 2013a). There has been a diverse range of silicic volcanism through non-explosive lava dome eruptions to block-and-ash flow generating violent eruptions (Moufti and Németh 2013a). Seeing these features coexist with features from basaltic and trachytic monogenetic volcanism is one of the most geologically intriguing aspects of the proposed geopark, in terms of understanding the origin of the evolved volcanism in dispersed, intra-continental systems commonly referred to as monogenetic fields.
The variety of trachytic lava domes exposed in is precinct are spectacular and they offer a good geoeducational program to build on them to link this geotopes and geosites to other well-known, recently erupted silicic lava domes, including Unzen in Japan (Kaneko et al. 2002; Yamashina and Shimizu 1999) and Mount St Helens (USA) (Anderson et al. 1995). The similarity in size, volume and eruptive products of the trachytic lava domes of the Harrat Al Madinah to those lava domes generally associated with subduction-related strato- and/or composite- volcanoes, makes the HAMVG truly unique and globally significant; and can make the proposed Harrat Al Madinah Volcanic Geopark as a potential “Makkah of Volcanologists” (Moufti and Németh 2013a). The scientific value of this precinct is self-defined. The perfect exposures, the lack of vegetable cover, the great visibility and the numerous longitudinal sections along gullies offer great research potential in these locations to scale the physical parameters of pyroclastic flow forming eruptions. In addition, the availability of pyroclastic deposit-engulfed scoria cones and other morphological obstacles can help to calibrate the energy budget of pyroclastic flows and therefore the precinct could serve as an important study location for such scaling volcanological work. Considering the “monogenetic volcanism” on display, this precinct offers a dramatically new view that will enable visitors to appreciate the complexity of such volcanism and see the link between focused (strato- and composite volcano-producing) and dispersed (purely monogenetic volcano-producing) magmatic plumbing system-associated volcanism, which will potentially make this volcanic geopark globally very significant (Moufti and Németh 2013a).
3.11.1 Matan Lava Dome Geotope [24° 13′ 31.71″N; 39° 50′ 23.56″E]
126.96.36.199 Geosite—Matan Lava Dome Side [24° 13′ 12.97″N; 39° 50′ 2.40″E]
188.8.131.52 Geosite—Matan Lava Dome Side Crater [24° 13′ 11.75″N; 39° 50′ 5.15″E]
In the southwestern side of the Matan lava dome complex a shallow, broad crater is visible that is surrounded by a low pyroclastic rim. This location can be accessed by walking track from the previous geosite through a gentle ascending path that take the visitor to the southern crater rim’s top. Along this walk, the visitor can examine the debris apron surrounding the main lava dome, a typical volcaniclastic debris apron that is composed of short run-out distance block-and-ash flow deposits mixed with fluvial and aeolian deposits and rock falls from the main dome region. The crater itself hosts voclaniclastic debris from the western segment of the Matan lava dome suggesting that it was formed earlier than the main lava domes. The crater rim is composed of welded pyroclastic rocks interbedded with some unconsolidated trachyte fragment-rich pyroclastic succession interpreted to be small-volume block-and-ash flow deposits. There are no clear indications to support magma and water explosive interaction as the main process to be responsible for the formation of the crater in spite the fact that the flat-floored crater and its broad shape very common among tuff rings. The significance of this geosite is to demonstrate that explosion craters can be common features in association with lava dome-dominate eruptions. The easy access and the rewarding fantastic view can be used as main promotion features to attract visitors to this site. In addition from this location the visitor can see the Mosawdah volcano and its extensive lava field just north of the Matan lava dome.
3.11.2 Mouteen Lava Dome Geotope [24° 12′ 51.79″N; 39° 50′ 38.82″E]
184.108.40.206 Geosite—Mouteen Lava Dome Hosting Cinder Cone [24° 13′ 3.80″N; 39° 51′ 11.35″E]
220.127.116.11 Geosite—Mouteen Lava Dome Main Dome Complex [24° 13′ 3.55″N; 39° 50′ 50.37″E]
This geosite can be accessed by further walking to the top of the Mouteen lava dome. The visitor can examine the lava dome material with great detail and in the end of the track the top of the lava dome can be explored where spines, rock falls and inter-dome aeolian silt pans can be seen. From the end of the track in the North of the Mouteen lava dome top perfect view shows the Matan lava dome and in the distance the Mosawdah cone and lava field.
3.11.3 Jabal Al Malsaa Matam Volcanic Complex Geotope [24° 12′ 18.43″N; 39° 51′ 6.65″E]
18.104.22.168 Geosite—Benmoreite Lava Flow [24° 11′ 35.78″N; 39° 51′ 21.37″E]
In the SW foothill of the volcano a spectacular benmoreite lava flow is exposed. The lava flow shows intensive flow banding and a very unique flow top morphology closely resembling clastic rock textures. In several places the flow is partially cross cut by wadis where the rock surface is more polished exposing the coherent texture of the rock. This geosite is important as it shows a graphic example to the visitor that the distinction between clastic and coherent rock textures is not easy when we deal with silicic rocks (McPhie et al. 1993). The disadvantage of this geosite is that it is difficult to access.
22.214.171.124 Geosite—Explosion Crater and View to the Main Cone [24° 11′ 41.26″N; 39° 51′ 21.13″E]
3.11.4 Um Junb Lava Dome Geotope [24° 11′ 59.43″N; 39° 53′ 27.63″E]
3.11.5 Dabaal Al Shamali Lava Dome Geotope [24° 13′ 20.02″N; 39° 54′ 19.07″E]
3.11.6 Gura 1 Explosion Crater Geotope [24° 13′ 5.58″N; 39° 53′ 29.36″E]
3.11.7 Gura 2 Explosion Crater Geotope [24° 12′ 11.68″N; 39° 52′ 42.02″E]
126.96.36.199 Geosite—Western and Northern Crater Rim
The crater rim of Gura 2 volcano can be accessed from the south. To the southern crater rim a 4WD track can take the visitor then a westerly round trip can be taken by foot to the northern rim. On the way to the southern crater rim lookout the path follow a typical block-and-ash flow fan surface littered by moderately vesicular trachyte lapilli and block hosted in a fine ash matrix. This rock texture is evident in the crater rim where proximal sections of the block-and-ash flow deposits exposed. Toward the north it is clearly visible how the pyroclastic flow deposits mantle over the disrupted trachytic lava domes as an older volcanic landform dissected by the explosive eruptions of Gura 2. This geosite has a high geoeducational value as it demonstrates clearly how crater formation, pre-existing volcanic landforms and the depositing pyroclastic successions from the disrupting explosive events form together the volcanic landscape.
188.8.131.52 Geosite—Eastern Gully [24° 12′ 11.33″N; 39° 53′ 4.83″E]
3.11.8 Gura 3 Explosion Crater Geotope [24° 11′ 22.71″N; 39° 52′ 24.36″E]
3.11.9 Al Shaatha Volcanic Complex Geotope [24° 8′ 39.75″N; 39° 53′ 35.62″E]
184.108.40.206 Geosite—Pyroclastic Flow Fan [24° 8′ 50.34″N; 39° 52′ 4.31″E]
220.127.116.11 Geosite—Trachytic Ash Plain [24° 7′ 50.00″N; 39° 53′ 56.61″E]
In the eastern side of the Al Shaatha volcanic complex, the terrain is covered by light coloured, pumiceous deposit forming an extensive ash plain that shown up clearly on the satellite images (Fig. 3.98). The ash plain is soft and aeolian remobilisation of pyroclasts is intensive. This geosite has a high geoeducational value as it can demonstrate the potential aftermath of a silicic eruption that covers large regions with fine, light coloured pumiceous ash. The frequent sand storms and the aeolian remobilisation of this sediment can provide valuable ideas to scale the devastation a large silicic pyroclast-producing explosive eruption can cause through block-and-ash flow inundation and airfall (Major et al. 2013; Pittari et al. 2006; Vernet and Raynal 2008). Also, the silicic ash plain shows numerous sedimentological features to better understand the resetting of the landscape after a major silicic ash-producing eruptions through various fluvial and aeolian processes similarly to those regions commonly experienced recent silcic eruptions (Aceves Quesada et al. 2014; Cuitino and Scasso 2013; Umazano et al. 2014). In this respect this geosite provide a complementary site to the basaltic ash plain sites such as those documented near the 1256 AD historic eruption site (Kawabata et al. 2015) as part of the proposed Precinct 1.
3.11.10 Gura 4 Explosion Crater Geotope [24° 6′ 47.80″N; 39° 55′ 56.70″E]
3.11.11 Gura 5 Explosion Crater and Block-and-Ash Fan Geotope [24° 6′ 14.86″N; 39° 57′ 9.94″E]
Gura 5 is a relatively small crater which is located relatively far from other craters (Fig. 3.100). The crater is unique by its appearance as being separated from other craters as indicates that it might represent a single explosive event that occurred in this region without any major development of lava domes. The peculiarity of this volcano is that it forma a rather positive landform and therefore it differs from the Gura 1 single explosion crater where the crater is clearly wide, broad and the tephra ring surrounding it inferred to have formed by phreatomagmatic explosions. Gura 5 is inferred to be a positive landform and probably erupted through moderate explosive eruptions of trachytic magma. There is no clear evidence to support phreatomagmatism in the formation of this volcano. This region also hosts another unique geological feature that has great geoeducational significance. Just west of the Gura 5 crater a deep canyon exposes a thick (30 m +) complex pyroclastic flow successions clearly deposited from multiple eruption events, and potentially from multiple sources. The landscape forms a flat surface that cut through deep box canyon where the typical block-and-ash flow units are exposed. The landscape is very unique in volcanic fields and it is more common feature in areas where long-lived silicic volcanoes exist, and produced multiple pyroclastic flow (e.g. ignimbrite) sheets that covered the landscape such as those in Tenerife (Brown and Branney 2013; Bryan et al. 1998; Garcia et al. 2011; Smith and Kokelaar 2013), or Central Anatolia (Aydar 1998; Le Pennec et al. 2005). This well-preserved “ignimbrite landscape” in spite its remoteness can provide a very unique view on Harrat Al Madinah and therefore this geotope and its geosites bear a major geoeducational value. This geotope shows clearly that on a volcanic field that is largely composed of basaltic volcanoes that erupted small-volume eruptive products that resulted mostly scoria cones and lava flows, extensive sheet like ignimbrite eruptions can take occur. This has a fundamental geohazard message. This geotope can provide to the visitor key information that this geotope and all the nearby sites as part of Precinct 3 can offer a very important volcanic hazard education tool for the public to be utilized through volcanic geoheritage, geoconservation and geotourism.
3.11.12 Um Raqubah Lava Dome Geotope [24° 5′ 23.44″N; 39° 57′ 45.18″E]
3.11.13 Al Efairia Volcanic Complex Geotope [24° 4′ 29.28″N; 39° 56′ 19.40″E]
Al Efairia is a large volcanic complex in the southern part of the Precinct 3 of the proposed HArrat Al Madinah Voclanic Geopark (Fig. 3.100). This complex volcano is best to be defined as a large silicic eruptive center that likely produced some shallow volcanic crater and multiple lava dome complexes. It closely resembling many complex lava domes sitting in silicic tuff rings in dome-tuff ring fields commonly reported from the geological record in various geotectonic settings (Brooker et al. 1993; Henry et al. 1997; Lexa et al. 2010; Riggs et al. 1997). The actual crater (or main eruptive vent) of the volcanic complex is difficult to reconstruct as just part of one of the crater is preserved well. The volcano also complicated by the fact that it has been erupted through a pre-existing scoria cone dominated volcanic chain that has been partially dissected by the formation of the Al Efairia volcano. It is also evident that the volcano had multiple vents and vent shifting produced some slightly migrated vent setting along lava domes formed. While the volcano proximal area is complicated and rather resembles a compound lava dome-dominated silicic volcano, the extensive block-and-ash flow fans are relatively simple and covering probably the largest surface area of the Harrat Al Madinah’s silicic volcanoes. This volcanic geotope has huge geoeducational significance as it provides the largest and most explosive style eruption scenario any volcanic hazard study needs to deal with in future eruptions in the Harrat Al Madinah region.
18.104.22.168 Geosite—Caldera View [24° 4′ 35.58″N; 39° 56′ 56.45″E]
22.214.171.124 Geosite—Half-Sectioned Pre-caldera Cone [24° 4′ 54.86″N; 39° 56′ 35.69″E]
126.96.36.199 Geosite—Al Efairia Lava Dome Complex [24° 4′ 29.28″N; 39° 56′ 19.40″E]
The lava domes of the Al Efairia volcanic complex are not as spectacular visually than optehr previously described lava domes, however they bear geological significance as they seem to grown into a broad crater formed the major and extensive block-and-ash fans derived from the AL Efairia volcanic complex. The lava domes expose flow banded trachyte that is partially flanked by short run-out distance block-and-ash flow deposits with coarse units. The geoeducational value of this geosite is the potential of the clear demonstration to the link between explosive and effusive phase of a silicic volcanic complex in the region. Similar relationships have been demonstrated elsewhere in the Precinct 3, however this site provides the most complex scenario and the largest volume of deposits.
188.8.131.52 Geosite—Complex Volcaniclastic Succession of a Block-and-Ash Fan [24° 4′ 8.49″N; 39° 56′ 38.49″E]
In the SW edge of the Al Efairia volcanic complex a well-developed block-and-ash fan is exposed. The block-and-ash fan shows perfectly the intermixing of primary and secondary deposits on this exposed gentle sloping region. The geosite has a geoeducational significance to demonstrate that in an active inter-con/inter-dome region primary and secondary volcanic processes together forming the landscape and the depositional environment. Moreover from this geosite the crater filling lava domes are clearly visible with their block-and-ash fan also fed material to the distal silicic ash plain.
3.11.14 Al Wabarah Volcanic Complex Geotope (Precinct 4) [24° 0′ 52.87″N; 39° 53′ 16.22″E]
3.12 Geopark Potential of the Harrat Al Madinah—A Discussion
Organisation of a geopark along volcanic features with high geoheritage value is the way to maximaze the potential of a region to be promoted successfully as a geopark. In this chapter it has been demonstrated that a systematic arrangement of volcanic geoheritage value of the Harrat Al Madinah has a great potential to provide firm scientific basis to develop and function a geopark in the region. The presented precinct concept showed a logical approach to demonstrate the volcanic geoheritage of the region which is by surface area very large, and by its logistical aspects need to be designed in a way that visitors can cover areas that present logically set geoheritage sites that all together can provide extra added value to understand not only the volcanism behind the formation of the Harrat Al Madinah, but also its volcanic hazards the local population faces with. The main aim to develop a volcanic geopark in the youngest volcanism in the Kingdom of Saudi Arabia is to show the fundamental geological features a typical harrat can have. Harrat Al Madinah with its perfect logistical background and proximity to a cultural focal point on Earth that act as a magnet of large number of visitors is a logical start point to develop projects that promote a geological feature in the Arabian peninsula, which is a very common landscape in the western Arabian region and has numerous cultural implications as well. We demonstrated that potential geoeducational routes and trails across Harrat Rahat, particularly in its northern sector, the Harrat Al Madinah can offer endless world-class geosites that can serve significant knowledge transfer on volcanic landscape evolution and understanding the volcanic hazards a young harrat may indicate. It has been demonstrates that some suggested visitor itineraries through a carefully design geological precincts and their geotopes and geosite could be logically linked together to demonstrate specific volcanic features or processes associated with dispersed volcanism such as formation of intracontinental volcanic fields. The international volcanological significance of the Harrat Al Madinah especially its potential link to volcanic researches on intracontinental volcanic fields hold the potential of its international linkages to similar trails with other volcanic regions’ geopark programs. The proposal and establishment of the HAMVG is the first such attempt in the territory of the Kingdom of Saudi Arabia. The success of this project will likely affect future geoconservation and geoeducation projects planned elsewhere in the Kingdom especially in other harrats. In the next chapters a brief summary will be given about the geoheritage and geoeducational potential of other, less known harrats of the Kingdom. In the following chapters we will not provide such detailed geosite level description of the geoheritage value of each of the harrats as such work would be way to extensive, but will provide significant link to Harrat Al Madinah, and will demonstrate the potential to develop a national network of volcanic geoparks that all together could even provide firm basis to apply candidature for being listed as a world heritage site as a fine example of dispersed intracontinental volcanism on Earth. The success of the Harrat Al Madinah Volcanic geopark potentially could provide an example for future similar activities elsewhere in the Arabian Peninsula and it could be designed as a flagship projects in the region. The impact of the proposed geopark on geotourism is expected to be huge. The Harrat Al Madinah’s volcanic geology is the perfect place to see a wide array of volcanic features, dramatic volcanic landscapes and the interaction between the extreme climate and volcanic landforms associated with intra-continental monogenetic volcanism. The Harrat Al Madinah is a globally unique intra-continental monogenetic volcanic field due to (1) the large number of young (<1 Ma) monogenetic volcanoes it hosts, (2) the wide range of chemical compositions of magma that formed the specific volcano types (from basaltic to trachytic), (3) the diverse eruption styles (e.g. from Hawaiian-style and Strombolian-style magmatic explosive eruptions to phreatomagmatic maar and/or tuff ring forming eruptions) and (4) the dramatically different volcanic landforms and associated volcanic rocks (e.g. from lava spatter cones and scoria cones to trachytic maar volcanoes and lava domes) that can be seen in a perfectly exposed manner. The diversity of volcano types in the proposed geopark that can be visited and seen perfectly is probably among the greatest in comparison to other intra-continental monogenetic volcanic fields. It is suggested that the proposed geopark is linked informally with geoeducation, geoconservational and geotouristic activities conducted and promoted by potential “sister geoparks” elsewhere, such as the Bakony- Balaton Geopark (Hungary), Nógrád/Novohrad Geopark (Slovakia/Hungary), Vulkaneifel Geopark (Germany), Jeju Island Geopark (Korea), Unzen Volcanic Area Geopark (Japan), Kanawinka Geopark (Australia) and Wudalianchi Geopark (China). These “sister geoparks” demonstrate volcanic features associated with similar types of volcanism to the Harrat Al Madinah, but with differences that make the parks complementary, including the level of vegetation cover (e.g. vegetation covered maars with lakes from the Vulkaneifel Geopark that are in contrast with the Harrat Al Madinah’s dry maars and explosion craters), exposure level (e.g. exposed volcanic conduits of similar monogenetic volcanoes to those at the Harrat Al Madinah are visible from the Bakony- Balaton and Nógrád/Novohrad Geopark), and variations in volcano types in accordance with variations in the volcanic eruption styles that formed them (e.g. active lava domes from Unzen Volcanic Area Geopark or the great size, shape and volcanic succession variations in Jeju Island, Korea). Linking and partially coordinating the scientific research, geoeducational/geoconservation programs and the geotouristic aspects of these “sister geoparks” would be a desirable approach in the future.
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