18 May 2008

Apocalypse Chile: Lightning from Mt. Doom?

Ominous rumblings accompany the startling images of lightning surrounding the erupting volcano, Mt. Chaiten in Chile. On the scale of volcanoes, Mt. Chaiten is building from a Plinian toward an Ultra-Plinian magnitude eruption.
I have been watching the eruption of Mt Chaitén in Chile, South America very closely for the last few weeks. It appears as if it may produce a major eruption soon. The last known eruption was in 7420 BC ± 75. The progress of the 2008 eruption has been as follows.

April 30: A significant earthquake preceded the first explosions;
May 2: More earthquakes arrayed radially around the caldera implying a very large magma chamber;
May 15: Near steady-state explosive eruptions (Plinian) releasing about two cubic kilometers of ejecta of 4-5km in altitude.

Eruptions are rated by the Volcanic Explosivity Index (VEI). The following are examples of recent eruptions and their VEI.

VEI=5 Plinian, ejecta > 1 km³, e.g. St. Helens (1980)
VEI=6 Plinian/Ultra-Plinian, ejects > 10 km³, e.g. Mount Pinatubo (1991)
VEI=7 Plinian/Ultra-Plinian, ejecta > 100 km³, e.g. Tambora (1815)
VEI=8 Ultra-Plinian, ejecta > 1,000 km³, e.g. Toba (73,000 BP) __NicheModeling
Chaiten began quite small, and has been building since. Seismic activity suggests the potential for much larger eruptions to come. Stay tuned.
Update 20May08:Image Source

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