Bulletin of Volcanology

, Volume 71, Issue 7, pp 815–826

Structure and CO2 budget of Merapi volcano during inter-eruptive periods

  • Jean-Paul Toutain
  • Francesco Sortino
  • Jean-Claude Baubron
  • Patrick Richon
  • Surono
  • Sri Sumarti
  • Anthony Nonell
Research Article

DOI: 10.1007/s00445-009-0266-x

Cite this article as:
Toutain, JP., Sortino, F., Baubron, JC. et al. Bull Volcanol (2009) 71: 815. doi:10.1007/s00445-009-0266-x

Abstract

Soil temperature and gas (CO2 concentration and flux) have been investigated at Merapi volcano (Indonesia) during two inter-eruptive periods (2002 and 2007). Precise imaging of the summit crater and the spatial pattern of diffuse degassing along a gas traverse on the southern slope are interpreted in terms of summit structure and major caldera organization. The summit area is characterized by decreasing CO2 concentrations with distance from the 1932 crater rim, down to atmospheric levels at the base of the terminal cone. Similar patterns are measured on any transect down the slopes of the cone. The spatial distribution of soil gas anomalies suggests that soil degassing is controlled by structures identified as concentric historical caldera rims (1932, 1872, and 1768), which have undergone severe hydrothermal self-sealing processes that dramatically lower the permeability and porosity of soils. Temperature and CO2 flux measurements in soils near the dome display heterogeneous distributions which are consistent with a fracture network identified by previous geophysical studies. These data support the idea that the summit is made of isolated and mobile blocks, whose boundaries are either sealed by depositional processes or used as pathways for significant soil degassing. Within this context, self-sealing both prevents long-distance soil degassing and controls heat and volatile transfers near the dome. A rough estimate of the CO2 output through soils near the dome is 200–230 t day−1, i.e. 50% of the estimated total gas output from the volcano summit during these quiescent periods. On Merapi’s southern slope, a 2,500 m long CO2 traverse shows low-amplitude anomalies that fit well with a recently observed electromagnetic anomaly, consistent with a faulted structure related to an ancient avalanche caldera rim. Sub-surface soil permeability is the key parameter that controls the transfer of heat and volatiles within the volcano, allowing its major tectonic architecture to be revealed by soil gas and soil temperature surveys.

Keywords

Volcano degassing Soil gases Imaging CO2 flux Ground temperature Volatile budget Geochemical imaging and prospecting 

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Jean-Paul Toutain
    • 1
    • 2
    • 3
    • 11
  • Francesco Sortino
    • 4
  • Jean-Claude Baubron
    • 5
  • Patrick Richon
    • 6
    • 7
  • Surono
    • 8
  • Sri Sumarti
    • 9
  • Anthony Nonell
    • 10
  1. 1.Université de Toulouse; UPS (OMP); LMTGToulouseFrance
  2. 2.CNRS, LMTGToulouseFrance
  3. 3.IRD, LMTGToulouseFrance
  4. 4.Istituto Nazionale di Geofisica e Vulcanologia, Sezione di PalermoPalermoItaly
  5. 5.JcbConsultingSandillonFrance
  6. 6.CEA, DIF, Service Radiochimie Chimie EnvironnementArpajonFrance
  7. 7.Equipe Géologie des Systèmes Volcaniques, IPGP, UMR 7154, CNRSParisFrance
  8. 8.DVGHMBandungIndonesia
  9. 9.MVO – Merapi Volcanological ObservatoryYogyakartaIndonesia
  10. 10.CEA, CEN SaclayGif sur YvetteFrance
  11. 11.LMTG, Université de Toulouse- CNRS-IRD-OMPToulouseFrance

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