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.
Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at
Igneous rocks (from the Greek word for fire) form from when hot, molten rock (magma) crystallizes and solidifies.
Volcanoes that produced exceedingly voluminous pyroclastic eruptions and formed large calderas in the past 2 million years would include Yellowstone, Long Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand.
Over the long term and geologic time, volcanic eruptions and related processes have directly and indirectly benefited mankind.
The major peaks in the US part of the Cascade Range are (from north to south) Mount Baker, Glacier Peak, Mount Rainier, Mount St.
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).
Several lofty volcanic peaks dominate the Cascade Range of the Pacific Northwest; the principal part of the range extends from
Debris flows pose the greatest hazard to people near Mount Rainier.
There are many paths to becoming a volcanologist. Most share a college or graduate school education in a scientific or technical field, but the range of specialties is very large.