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The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982.
For larger volcanoes that have erupted at least 1,000 km 3 (240 cu mi) of tephra at a time, see Category:VEI-8 volcanoes or Category:Supervolcanoes. The only unambiguous VEI-7 eruption to have been directly observed in recorded history was Mount Tambora in 1815 and caused the Year Without a Summer in 1816.
The magnitude was 7 on the Volcanic Explosivity Index (VEI) scale, with a total tephra ejecta volume of up to 1.8 × 10 11 cubic metres. [25] Its eruptive characteristics included central vent and explosive eruptions, pyroclastic flows, tsunamis and caldera collapse. This eruption had an effect on global climate.
Considered "brother and sister" mountains, the two volcanoes are approximately 50 miles (80 km) from Mount Rainier, the highest of the Cascade volcanoes. Mount Hood, the nearest major volcanic peak in Oregon, is 60 miles (100 km) southeast of Mount St. Helens. Mount St. Helens is geologically young compared with the other major Cascade volcanoes.
Volcanic eruptions that rated 5 on the volcanic explosivity index. Such eruptions release a tephra volume of at least 1 km 3 (0.24 cu mi) with immediate exceptional effects on the surrounding area. For smaller volcanic eruptions that have produced at least 0.1 km 3 (0.024 cu mi) of tephra at a time, see Category:VEI-4 eruptions.
Category: Volcanoes by highest known Volcanic Explosivity Index of eruption. ... VEI-2 volcanoes (11 P) VEI-3 volcanoes (1 C, 12 P) VEI-4 volcanoes (2 C, 39 P)
Tuff Canyon: volcanoes erupted 30 million years ago and expelled basalt lava rocks and hardened volcanic ash Davis Mountains: 35 million years old and formed by magma from two volcanic centers
Volcanic eruptions that rated 4 on the volcanic explosivity index. Such eruptions release a tephra volume of at least 0.1 km 3 (0.024 cu mi) with substantial effects on the surrounding area. For smaller volcanic eruptions that have produced at least 0.01 km 3 (0.0024 cu mi) of tephra at a time, see Category:VEI-3 eruptions .