Volcanoes General

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.
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.
Mount St. Helens, Washington 2004-2007: Volcanic dome growth renewed on September 20, 2004 and has been continuous.
The May 18, 1980 eruption of Mount St. Helens (Washington) was the most destructive in the history of the United States.
Climb A Volcano - 'Family Fun - Picnic at the Top'
The USGS Photo Glossary of volcanic terms includes photo examples of each term.  
All these links have volcano information: USGS Volcano Observatories
The United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes (that is, those for which we have written accounts of eruptions).
Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America.