Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufm.v52a1050k&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #V52A-1050
Physics
0370 Volcanic Effects (8409), 6225 Mars, 8409 Atmospheric Effects (0370), 8429 Lava Rheology And Morphology, 8450 Planetary Volcanism (5480)
Scientific paper
Rubbly pahoehoe flows consist of a brecciated flow top, a pahoehoe base, and an interior similar to inflated pahoehoe flows. Rubbly pahoehoe flows can be found in many localities, making up ~20% of the Columbia River Basalt Group, ~50% of the lavas drilled on the Kerguelen Plateau, and a substantial fraction of the Icelandic lava flows. They are rare in the tholeiitic shield portions of the Hawaiian volcanoes, but are more common in the alkalic flows. They also appear to be the dominant type of Martian flood lava flow. Based primarily on observations from the 1873-1874 Laki Flow Field in Iceland, we suggest that rubbly pahoehoe flows form when the flux of lava within an inflating pahoehoe flow is so large that it rafts away the upper crust. This crust is then broken into large slabs and fragmented lobes, intruded by liquid lava from below, and folded into pressure ridges. This brecciation process quickly builds an insulating crust; for the Laki case a crust >4 m thick developed in less than a week. This rapid formation of a thick insulating crust allows lava to be transported over great distances with minimal cooling in eruptions lasting only weeks-months. Flood basalt flows emplaced in this manner could have had eruption rates on the order of 104 - 105 m^{3}s^{-1}. If active fissure segments were of the order of 10 km long, the volcanic plumes should have risen 9-16 km -- penetrating the stratosphere in most cases. The injection of \sim10 Gt of SO_{2}$, F, and Cl into the stratosphere could have had serious climatic effects, thus further strengthening the plausible link between flood basalt eruptions and mass extinctions.
Keszthelyi Laszlo
Self Stephen
Thordarson Th.
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