Geologic history of Washington stretches back more than a billion years and has survived through violent volcanic eruptions, large-scale earthquakes and even an Ice Age which gave the land much of it’s current look. Around 1.2 billion years ago, the lands on Earth began to push together and plate tectonics created a giant continent known as Rodinia, which is Russian for “homeland.” This was the dominant landmass of Earth for nearly 350 million years. Western North America used to lie next to what is now Australia and Antarctica. This world was a dark and hostile one, where the only life to exist was probably single-celled organisms. Oxygen in the atmosphere was only 5% of what it is today, and

4. The Cascade Episode (37 million years to the present).

3. The Challis Episode (57-37 million years)

The Paleozoic Era was a quiet one, in which Washington experienced little action. It was during the Cambrian Period that the first major groups of animals started to appear off it’s shore 540 million years ago. Fish started to appear in the Ordovician Period 500 million years ago, and plants sprouted on the land during the Silurian Period 420 million years ago. Then somewhere during the Devonian Period some 370 million years ago the oceanic plate plunged underneath the continent and created a new subduction zone ending a peaceful 400 million years of inactivity.

During the Omineca Episode, the Intermontane Islands collided and welded to the continent, and adjacent to where the island used to appear, a group of volcanoes rose out of the ocean. The Coast Range Episode is when another chain of volcanic islands collided with the continent and molded into it. Both during the Omineca and Coast Range Episodes the rock that crashed into the continent was crushed and folded, forming mountains and volcanoes. Since the islands were so massive, they couldn’t just fo underneath the continent, so they formed new subduction zones. The volcanoes and mountains have since been lost due to erosion. The Challis Episode brought upon a folding and re-arranging of the Pacific Northwest. This is the most active and drastic Period in the geologic history of Washington. Eventually, Washington is buried in sediment mostly sand and silt, which preserved fossils of the time, which include palm trees, which give the coast a tropical setting of that time period. Finally there is the Cascade Episode, which brings us up to present time. The Cascade Range of mountains contain erupting volcanoes which continue to shape the region. 17 million years ago, the eastern part of Washington was

Some topics in this essay:
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