The Geologic History of Washington State & Kittitas County. Jana Jones Mabry. Geologic History of Washington State. Overview of the processes responsible for the underlying geology Overview of different geologic provinces of the state
Jana Jones Mabry
The North American Continental Coastline was located approximately 30 miles west of the the present day border of Idaho and Washington
The last event to add to the Washington coastline was approximately 25 million years ago is called the Crescent Terrane located in the areas of the Puget Lowlands, Olympic Peninsula and the Willapa Hills
The last significant volcanic events to shape the Washington landscape were the birth of the Cascade Volcanoes between 1 million and 75,000 years ago
The Ice Sheet and Glaciers that have occurred over the past 2million years have had a significant impact on the topography of this area.The Yakima Glacier flowed from the Snoqualmie Summit to Thorp The three depressions now holding Keechelus, Kachess and Cle Elum Lakes held glaciers that fed into the main stream Yakima Glacier.It created the U-shaped valley in which the present day Yakima River flows and covered the bedrock geology of the whole area with glacial debris and alluvial (water deposited) materials.
Lake Easton is a man made lake created where the Yakima and Kachess Rivers come together. This reservoir was built 1928 through excavation and removal of the glacial till.Its primary function is to supply water for the agriculture of south-central Washington and a variety of recreational activities to the central region. The view to the east of the park provides a glimpse into the rich geologic history of the region