The Hawaiian shield volcanoes are the largest mountains on Earth.
Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet made it only the fifth highest peak in Washington State.
During the 9 hours of vigorous eruptive activity, about 540 million tons of ash fell over an area of more than 22,000 square miles.
The eruptive history of Mount St. Helens (Washington) began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago.
The principal volcanoes of the Hawaii Islands (from northwest (oldest) to southeast (youngest)) are Niihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe, and Hawaii (Big Island).
Can an eruption at one volcano trigger an eruption at another nearby volcano (for example, within about 10 km)?
There are a few historic examples of simultaneous eruptions from volcanoes or vents located within about 10 km of each other, but it's very difficult to determine whether one might have caused the other.
Yes. Crater lakes atop volcanoes are typically the most acid, with pH values as low as 0.1 (very strong acid). Normal lake waters, in contrast, have relatively neutral pH values near 7.0.
Yes. Encounters between aircraft and clouds of volcanic ash are a serious concern.
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