Also, unlike Crater Lake, Okmok has erupted in the 21st century – a VEI 4 eruption in 2008-09.ģ. Unlike Crater Lake, the 100 BCE collapse was the second for Okmok, following one that occurred ~12,000 years ago. Okmok has always looked to me a lot like a drained Crater Lake and that’s because it too was formed by a massive eruption that prompted a collapse of the volcano. Okmok’s eruption in 100 BCE leads the pack. Most on this list are in the Aleutians, although a pair are found further east in the Wrangell Range. Now we start our tour of Alaskan volcanoes. Okmok : VEI 6, mag 6.7, 100 BCE, 29 cubic kilometers It is hard for me to fathom what the impact of such an eruption would be if it happened today in the Cascade Range.Ģ. Oregon’s Crater Lake (called Mazama when discussing it before there was a lake) was formed in this cataclysmic eruption, likely close to the largest, if not the largest, on record in the modern Cascade (The Rockland Tephra from the Lassen Volcanic Center was also ~30-50 cubic kilometers). The big one … and the only one in the top 10 outside Alaska. All the volumes here are DRE.Ī view of the Crater Lake from the Watchman Lookout Tower. This is a calculation using data about the percent of air in the deposit that then removes the volume of air to get at how much magma was actually erupted. Material like that tends to be full of air pockets, so to put all eruptions on an even playing field as the amount of air can vary, we convert it to a “dense rock equivalent” or DRE. First, explosive volcanic eruptions produce tephra, with is a bit of a catch-all for volcanic debris like ash, pumice, bombs, etc. I used the Smithsonian Institution Global Volcanism Program and the Volcano Global Risk Identification and Analysis Project (VOGRIPA) databases for my information.Ī few things about measuring volcanic eruptions. To try to normalize thing, I considered “biggest” to mean largest volume of erupted material, the higher eruption magnitude and then the eruption’s volcanic explosivity index (VEI in the at order). As you will see, this can be a tricky question. So, I present you with the largest eruptions in the US over the last 10,000 years. This got me wondering what are the biggest eruptions the US has experienced and that led me down a rabbit hole considering what that question actually means. Sure, a large swath of it east of the Rocky Mountains haven’t had an eruptions of tens to hundreds of millions years, but the western US, Alaska and Hawai’i are all full of active or potentially active volcanoes.
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