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BC
Geology
Around 700 million years ago, the Pacific Ocean covered most of the western provinces and states. Several times over the next half billion years, the ocean advanced and receded, each time depositing layers of silt and sand on its bed that built up with each successive inundation. After around 150 million years, the oceans became home to marine invertebrates and the first crustaceans, which added to the layers of sediment. These sediments were compressed over time into sandstone, shale, and quartzite.
75 million years ago, the Pacific Plate butted into the North American Plate and was forced beneath it. The Rocky Mountains were created as the land at this subduction zone crumpled and thrust upward. Layers of sediment were folded, compressed and rotated, and within 10 million years the present form of the Rocky Mountain chain’s contours was established. Tectonic activity continues to occur off the west coast of Vancouver Island, causing earthquakes and the slow transformation of BC’s land masses.
Around one million years ago the world's climate began to cool and warm by a few degrees. Ice caps formed in Arctic regions and advanced south and retreated north over North America and Eurasia four times. The final major glaciation began moving south 35,000 years ago. A sheet of ice up to 2,000 meters (6,560 feet) deep covered all but the highest peaks of the Rocky Mountains. The ice scoured the terrain, carving hollows into the slopes of the higher peaks. The retreat of this ice sheet, beginning around 12,000 years ago, also radically altered the landscape.
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