Syn- and post-eruptive mechanism of the Alaskan Ukinrek Maars in 1977
The two alkali olivine basaltic Ukinrek Maars (East Maar and West Maar) and one scoria cone within East Maar erupted within eleven days (March 30–April 9, 1977) on the Alaskan Peninsula, 13 km north of Mt. Peulik, an andesite volcano of the Aleutian Range. The East Maar, with a diameter of 300 m, is located within a small graben system striking N 1100 E, oblique to the Aleutian trench in a distance of 350 km. On these tensional faults two eruption centres occur: The East Maar and a scoria cone on the southeastern margin of its crater bottom. The scoria cone was active more or less during the whole eruption activity of East Maar. The West Maar, with a diameter of 140 m, is located just west of the East Maar. In the West Maar, after the first of three eruption cycles, feeder dike fragments were thrown out. They indicate that the explosion chamber migrated downwards during the maar formation. After the eruption activity, both craters filled up with ground-water and the coneshaped talus fans continued to grow on the crater floors, modified by gravity sliding and lahars.
KeywordsScoria Cone Tundra Soil Crater Wall Crater Floor Juvenile Clast
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- Dreibus, G.; Graup, G.; Lorenz, V. & Wänke, H. (1986): Int. Volcanol. Congr., Hamilton, New Zealand, abstracts, p. 147.Google Scholar
- Estabrook, C.H. & Jacob, K.H. (1991): Stress indicators in Alaska. In: Slemmons, D.B., Engdahl, E.R., Zoback, M.D. & Blackwell, D.D. (eds.), Neotectonics of North America, 387–399, Geol. Soc.; Boulder, Colorado.Google Scholar
- Fisher, R.V. & Schmincke, H.-U., (1984): Pyroclastic rocks. 472 p., Springer, Berlin.Google Scholar
- Larter, R.C.L. & Allison, I. (1983): An inexpensive device for modelling strike-slip and oblique-slip fault zones. J. Geol. Educ., 31: 200–205.Google Scholar
- Lorenz, V. (1985): Maars and diatremes of phreatomagmatic origin, a review. Trans. Geol. Soc. S. Afr., 88: 459–470.Google Scholar
- Lorenz, V. & Zimanowski, B. (1983): Fragmentation of alkali-basaltic magmas and wall-rocks by explosive volcanism. In: Kornprobst, J. (ed.), Kimberlites. III: Documents, 15–25, Ann. Sci. Univ., Clermont-Fd.Google Scholar
- Nakamura, K. & Uyeda, S. (1980): Stress gradient in arc-back regions and plate subduction. J. Geophys. Res., 85: 6419–6428.Google Scholar
- Stone, D.B. & Wallace, K.W. (1987): A Geological framwork of Alaska. Episodes, 10: 283–289.Google Scholar
- Wasburn, A.L. (1979): Geocryology. A survey of periglacial processes and environments. 406 p., Edward Arnold; London.Google Scholar