I was an invited expert on the 12 day field excursion through the USA Cascade Mountains by the 3rd year students from University of California - Los Angeles (UCLA). With the main aim to climb and examine as many volcanoes as possible with the climax of going inside the crater of Mount St Helens.
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia (Canada) through Washington and Oregon to Northern California.
The Cascades extend from Lassen Peak (also known as Mount Lassen) (3170 m) in northern California to Lytton Mountain (2,049 m) in Canada, just southeast of the confluence of the Fraser and Thompson Rivers.
The Cascades are part of the Pacific Ring of Fire, the ring of volcanoes and associated mountains around the Pacific Ocean. The Pacific (tectonic) Plate is descending beneath the western part of the USA. All of the known historic eruptions in the USA have been from Cascade volcanoes. The two most recent were Lassen Peak in 1914 to 1921 and a major eruption of Mount St. Helens in 1980. Minor eruptions of Mount St. Helens have also occurred since, most recently in 2006.
The Columbia River Gorge is the only major break in the American part of the Cascades. When the Cascades started to rise 7 million years ago in the Pliocene, the Columbia River drained the relatively low Columbia River Plateau. As the range grew, the Columbia River's erosive power was able to keep pace, creating the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau.
