High velocity debris avalanche at Lastarria volcano in the north Chilean Andes
- 116 Downloads
A pre-historic collapse of the southeast flank of Lastarria volcano (∼ 5700 m) in the north Chilean Andes (25° 10′ S), produced a fluidized volcanic debris avalanche whose morphology and surface structures are exceptionally well preserved. The avalanche travelled to the east-south-east, covering an area of 9.3 km2, and came to rest after climbing and over-riding a 125 m high older scoria cone. The 0.091 km3 avalanche has an apparent coefficient of friction (H/L) of 0.15 and an excessive travel distance index (Le) of 5.1 km, indicating high emplacement velocity, perhaps of the order of 80 m s−1. An important cause of the high mobility may have been the predominance of low-density, poorly cohesive scoriaceous and pumiceous layers in the source region. The flow may have had properties similar to those of a small ignimbrite.
KeywordsSurface Structure Source Region High Mobility Sedimentology Travel Distance
Unable to display preview. Download preview PDF.
- Francis PW, Baker MCW (1977) Mobility of pyroclastic flows. Nature 270: 164–165Google Scholar
- Francis PW, Gardeweg M, Ramírez CF, Rothery DA (1985) Catastrophic debris avalanche deposit of Socompa volcano, northern Chile. Geology 13: 600–603Google Scholar
- Hsü KJ (1975) Catastrophic debris streams (Stutzstroms) generated by rockfalls. Geol Soc Am Bull 86: 129–140Google Scholar
- Nakamura Y (1978) Geology and petrology of Bandai and Nekoma volcanoes. Sci Rep Tohohu UnivGoogle Scholar
- Naranjo JA (1986) Geology and evolution of the Lastarria volcanic complex, north Chilean Andes. Unpublished M Phil thesis, Open University, EnglandGoogle Scholar
- Plafker G, Ericksen GE (1978) Nevado de Huascarán avalanches, Peru. In: Voight B (ed) Rockslides and avalanches, I. Elsevier, Amsterdam, 277–314Google Scholar
- Reiche P (1937) The toreva block. A distinctive landslide type. J Geol 45: 538Google Scholar
- Schultz PH (1976) Moon Morphology. University of Texas at Austin; p 626Google Scholar
- Siebert L (1984) Large volcanic debris avalanches: characteristics of source areas, deposits and associated eruptions. J Volcanol Geotherm Res 22: 163–197Google Scholar
- Ui T (1983) Volcanic dry avalanche deposits- identification and comparison with non-volcanic debris stream deposits. J Volcanol Geotherm Res 18: 135–150Google Scholar
- Voight B, Glicken H, Janda RJ, Douglass PM (1981). Catastrophic rockslide avalanche of May 18. In: Lipman PW, Mullineaux DR (eds) The 1980 eruptions of Mount St. Helens, Washington. US Geol Surv Prof Pap 1250: 347–378Google Scholar