Year after year this rift continued to grow and it eventually created a vast ocean basin known as "Panthalassic Ocean," a Greek word meaning "all the seas." As the rift began to split apart from what is now Eastern Washington and Antarctica, it pushed the two continents away from each other. The broken edge where the continents broke apart from each other became tectonically quiet for 400 million years, leaving it drastically less active than it is now. 600 million years ago this region went through glaciation, which is the earliest known Ice Age.
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.
Pangea brought the continents back together and formed another super continent during the later half of the Paleozoic Era. When the Permian Period rolls around nearly 300 million years ago, the super continent was completely formed once again. It was during this time that mu7ch of North America had become desert, and it was these changes that may have contributed to a mass extinction where near 90% of all species were eliminated, and is the largest extinction in the Earths history, even larger than the Dinosaur extinction. Pangea lasted throughout most of the Permian and Triassic Periods a span of some 100 million years. Sediment collected under shallow seas of the continental shelf of Eastern Washington. Life started to recover to a great extent, including Dinosaurs. Than 200 million years ago Pangea started to break apart.
