page_title: Columbia River Gorge
section_title: Geology
hierarchical_section_title: Columbia River Gorge / Geology
caption_attribution_description: English: A view of the Columbia River Gorge from the near the top of Hamilton Mountain, looking south from the Washington state side of the gorge. On the left side of the image, the Bonneville Dam is visible. On the left-center is the small town of North Bonneville. Behind the hills in the center of the image, the peak of Mt. Hood is just barely visible. The large rock at the river's edge on the right side is Beacon Rock.
context_page_description: The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to 4,000 feet deep, the canyon stretches for over eighty miles as the river winds westward through the Cascade Range, forming the boundary between the state of Washington to the north and Oregon to the south. Extending roughly from the confluence of the Columbia with the Deschutes River in the east down to the eastern reaches of the Portland metropolitan area, the water gap furnishes the only navigable route through the Cascades and the only water connection between the Columbia Plateau and the Pacific Ocean. It is thus the route of Interstate 84, U.S. Route 30, Washington State Route 14, and railroad tracks on both sides.
  A popular recreational destination, the gorge holds federally protected status as the Columbia Gorge National Scenic Area and is managed by the Columbia River Gorge Commission and the U.S. Forest Service.
context_section_description: The Columbia River Gorge began forming as far back as the Miocene (roughly 17 to 12 million years ago), and continued to take shape through the Pleistocene (2 million to 700,000 years ago). During this period the Cascade Range was forming, which slowly moved the Columbia River's delta about 100 miles (160 km) north to its current location.
  Although the river slowly eroded the land over this period of time, the most drastic changes took place at the end of the last Ice Age when the Missoula Floods cut the steep, dramatic walls that exist today, flooding the river as high up as Crown Point. This quick erosion left many layers of volcanic rock exposed.
caption: A view of the Columbia River Gorge from near the top of Mt. Hamilton, looking south from the Washington side of the gorge. On the far left side of the image, the Bonneville Dam is visible. On the left-center is the small town of North Bonneville. Behind the hills in the center of the image, the peak of Mt. Hood is just barely visible. The large rock at the river's edge on the right side is Beacon Rock, which is 848 feet (258 m) tall. The high point to the right of center is Nesmith Point, the highest point on the rim of the gorge at 3,848 feet (1,173 m).
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