Geologic History of WA Washington 200+ Million Years Ago

Plate Tectonics at Work in WA!

http://www.youtube.com/watch?v=wkc4lbhhSRs&feature=related

http://www.dnr.wa.gov/researchscience/topics/geologyofwashington/pages/willapa.aspx Geologic History of WA Washington 200+ million years ago

OCEAN!!!! Kootenay Arc & Okanogan Highlands Geologic History of WA

Kootenay Arc 200 million years ago

North America coastline is about where Spokane is today. Subduction zone to the west of the coast. Ocean seabeds N America

Bird’s Eye

Trench

Seabed layers lie on top ocean plate. Early seabeds They get scraped off when Pacific N Am They collide with N Anerica plate Ocean Geologic History of WA

Kootenay Arc 200 million years ago

Ocean N America

Bird’s Eye

Trench

Kootenay Arc – As seabeds get scraped off, they Early seabeds are folded into the coastline. Pacific N Am Ocean This extending the coastline further west of present day Spokane Kootenay Arc: Metamorphic, Igneous, or Sedimentary?

Metamorphic

- Existing rock (old sea beds) subjected to pressure and heat WA 200 million years ago WA – 180 million years ago - arrival of Okanogan Microcontinent - Geologic History of WA

Okanogan Micro-Continent 180 million years ago

Kootenay Arc 1) Okanogan continent is 1) on the ocean plate & collides with the coast of North America as plate slides under continent.

2) The micro-continent 2) locks up or jams the ocean plate’s movement

New Trench 3) The pressure builds, 3) forcing the ocean plate to break behind the microcontinent, forming a new trench. Okanogan Micro-Continent -Bird’s eye view

Kootenay

Trench New Trench formed WA – 180 million years ago after collision! - WA 115 million years ago - arrival of North Cascades Microcontinent - Geologic History of WA

115 million years ago North Cascades Micro-Continent

1) North Cascades micro- N. Cascade continent is on the ocean 1) plate & collides with North America.

2) The micro-continent 2) locks up or jams the ocean plate’s movement

3) The pressure builds, forcing the ocean plate to break behind the island 3) continent. WA 115 million years ago - after collision of N Cascades - Olympic Mountains & Willapa Hills 50-20 million years ago - Geologic History of WA

Olympic Mountains Willapa Hills 50-20 million years ago

N America Pacific

Basalt beds

Basalt layers on the ocean plate are thrust forward into North American plate, as ocean plate slides under what is Washington.

This creates a wedge of crust that rises upward, forming the Olympic Mountains & Willapa Hills. Olympic Mountains—Willapa Hills 50 - 20 million years ago -

Was there land in this white space? - Yes! But, the lands in the white area were covered over and altered by later events, such as…. Columbia Plateau Basalt Flows –Columbia Plateau 18 - 15 million years ago

Cracks form in the crust in Rising basalt magma eastern Washington, Oregon, and southern Idaho.

Basalt flows upward through the cracks and flows over the region

Columbia Basin Basalt Flows Basalt Flows –Columbia Plateau Cascade Mountains Cascade Mountain Formation 5 million years ago

Olympics Cascades Friction caused by subduction of the ocean plate underneath Washington, creates magma and moves rising magma upward to form volcanoes.

Cascade Mountains Puget Sound Lowlands Geologic History of WA

25,000 -11,000 years ago Ice Age

Mile thick ice sheet covers most of Canada with a large finger of ice carves out Puget Sound. The Great Flood The Great Flood

Geology of WA Recap 1) Kootenay Arc folded sea beds 2) Okanogan Microcontinent Island collision 3) North Cascades Microcontinent Island collision 4) Olympic Mountains / Willapa Hills Sea beds wedge into Olympic Penisula forcing uplift of land 5) Columbia Plateau Basalt flows 6) Cascade Mountains - volcanoes - 7) Ice Age

a) Puget sound Basin formed

b) Great Flood in E WA