Metropolitan Portland, Oregon, like Auckland, New Zealand, includes most of a Plio-Pleistocene volcanic field.
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.
Eruptions in the Cascades have occurred at an average rate of 1-2 per century during the last 4000 years, and future eruptions are certain.
The Alaska Peninsula and the Aleutian Islands have about 80 major volcanic centers that consist of one or more volcanoes.
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.
Alaskan volcanoes have produced one or two eruptions per year since 1900.
During the past 10,000 years, about 60 giant debris flows from Mount Rainier have filled river valleys to a
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