Michael Manga on Wet Eruptions
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In the podcast, Michael Manga talks about the various ways in which the presence of water can affect eruptions, both here on Earth and elsewhere in the Solar System. Most dramatically, it can vastly amplify the explosive power of a volcanic eruption. The 2022 Hunga Tonga eruption, the most powerful eruption in a lifetime, was a good example of this.
Manga is a Professor in the Earth and Planetary Science department of the University of California, Berkeley.
Podcast Illustrations
Eruption of Mount St. Helens in 1980. During the eruption, the flank of the volcano collapsed.
Eruption of Mount Pinatubo in 1991. The ash cloud reached the stratosphere and caused about 0.5°C of cooling for several years. The Hunga Tonga eruption was comparable in explosive power to this eruption.
Hunga Tonga eruption, 15 January, 2022. As Manga says in the podcast, this was the largest eruption in our lifetimes. The plume reached a height of 58 kilometers and the explosion was heard in Alaska, 8,000 km away. The explosive power stemmed from the conversion of thermal energy to kinetic by the sudden conversion of a large amount of water to steam. The eruption took place at a depth of 850 meters, well above the ~2,200-meter depth below which the pressure is too great for magma to create steam.