This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 1 GEOLOGY 20 - LECTURE 1 CALIFORNIA VOLCANOES OF THE CASCADES (Ch. 5) California is divided into several geomorphic provinces based on their distinct geology and landscapes. “ geomorphology ” just refers to the characteristic landscape of an area which is a function of its geology, climate and topography. Cascades The Cascades are a 500-mile-long chain of volcanic peaks (up to 14,000’ high), covered by temperate rain forests and small glaciers near their peaks. Cascades extend from Northern Calif., Oregon, and Washington to southernmost British Columbia The modern Cascades are important to understand because they provide a model for what the ancestral Sierra Nevada may have looked like about 100 m.y.a. (m illion y ears a go) (You’ll see how these two geomorphic provinces directly relate to one another as the class progresses. You’ll also become familiar with time intervals in the millions of year range.) - all of the 14 major volcanoes in the chain are active and hazardous, as evidenced by the 1980 eruption of Mt. St. Helens.- Mt. Rainier outside Seattle is considered to be the most hazardous volcano in the United States because of its proximity to major urban areas - Mt. Lassen and Mt. Shasta in California are just as potentially active as any Cascades volcano, but their danger is not considered to be as high as other volcanoes due to the lack of dense population around their peripheries. Volcano Basics . . . Some volcanoes erupt primarily lava (like ‘red’ eruptions in Hawaii), while others erupt massive clouds of ash and debris (in addition to lava). - volcanoes of the Cascades predominantly erupt ash and other debris, as well as the occasional lava flow (aka, ‘gray’ eruptions) - over millions of years and countless eruptions, the alternating layers of lava and ash accumulate to build volcanoes upward: volcanoes built this way are called stratovolcanoes- (other than Mt. Lassen) most Cascade volcanoes are stratovolcanoes, which have the classic “inverted cone” shape that we typically associate with volcanoes. They are capped by a summit crater from which most eruptions occur. from which most eruptions occur....
View Full Document
This note was uploaded on 04/22/2008 for the course GEL 20 taught by Professor Osleger during the Spring '08 term at UC Davis.
- Spring '08