The Olympic Mountains
The Olympic Mountains are made up of a large uplifted and folded section of oceanic crust that was added to the continent at the margin of the Cascadia subduction zone. The accumulation of oceanic crust began to move slowly towards the North American continent via subduction. Subduction occurs when shifting tectonic plates cause dense rocks (like oceanic crust) to subduct, or shift beneath lighter, less dense rocks (like continental crust).
There are three main rock types in the Olympics:
- Sandstone- Sedimentary rock comprised of sand-sized mineral, other rocks, and/or organic material
- Shale- Sedimentary rock that is soft and stratified and formed from consolidated mud or clay. It can be split easily into slabs.
- Basalt- igneous rock that was once erupted from underwater volcanoes.
Three processes have been working to erode the mountain landscape: running water, glacial ice, and gravity.
- The rivers high in the mountains support a rainfall of 140 to 200 inches per year as it drains to the ocean.
- The alpine glaciers remain from the most recent ice age 2 million years ago. The Cordilleran Ice Sheet moved from west Canada to Washington into the Puget Sound region and split into to lobes as it encountered the Olympics. One lobe went into the Strait of San Juan de Fuca and the other to the Puget Lowland. The image below shows common features of an alpine glacier.
Information Retrieved From:
-http://www.nature.nps.gov/geology/parks/olym/
-http://www.dnr.wa.gov/programs-and-services/geology/explore-popular-geology/geologic-provinces-washington/olympic#mineral-resources
-http://www.nature.nps.gov/geology/parks/olym/
-http://www.dnr.wa.gov/programs-and-services/geology/explore-popular-geology/geologic-provinces-washington/olympic#mineral-resources