The similar to 23,500 y(14)C BP White Pumice Plinian eruption and associated debris avalanche and Tochimilco lava flow of Popocatepetl volcano, Mexico

摘要

The White Pumice (WP) is one of the thickest and most voluminous Plinian fallouts produced by Popocatepetl volcano in central Mexico during the Late Pleistocene-Holocene. Its eruption similar to 23,500 C-14 y BP (27,800 cal BP) was triggered by the catastrophic failure of the SW flank of the volcano. The resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction (L/H) of 0.06. The deposit covers an area of similar to 1200 km(2), and has a volume of 10.4 km(3). This gigantic landslide, characterized by exceptionally large proximal hummocks (>400 m) provoked the sudden decompression of the hydrothermal and magmatic systems, which produced an initial blast followed by the rise of a Plinian column that reached an altitude of similar to 33 km. The isopach map allows the recognition of a dispersal axis pointing toward the south, where an area of similar to 2490 km2 was covered by >10 cm of pumice and ash. The total volume of the pumice fallout was estimated at similar to 1.9 km3 DRE (Dense Rock Equivalent). Pumice clasts are dacitic (62-66 wt.% SiO2, anhydrous basis), highly vesicular (55-88 vol.%) and display a sedate texture with phenocrysts of plagioclase + hornblende + augite + hypersthene + oxides (Ti-magnetite and ilmenite) + apatite.