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By: BriarCraft, 6:18 PM GMT on June 13, 2012
The Columbia River Gorge is something special to behold. It is easy to forget the scale of what you are looking at until you focus on something man-made and notice just how tiny it looks. The Gorge is 80 miles long and up to 4,000 feet deep where the river carves through the Cascade Mountains on its way to the sea. How could a river, even one as big as the Columbia, carve through a mountain range?
The Cascade Mountains are volcanic in origin and 20-40 million years ago, they dumped layer upon layer of ash, lava, and mudflows on the region. 12-17 million years ago, cracks opened in the earth's crust several miles long. Out of these cracks poured basalt floods. Approximately 270 lava flows spread across the region and 21 of those poured through the Gorge forming layers of rock up to 2,000 feet deep. Many of these lava flows cooled into columnar basalt; the lava cracks, forming six-sided columns. 700,000 to 2 million years ago, the Cascades began to uplift. As the mountains rose, the Columbia carved its way through, creating the only near-sea level passage through the Cascades.
14-16,000 years ago, during the last ice age, glaciers covered Canada and descended into the present-day panhandle of Idaho, blocking the Clark Fork River with a 2,000 foot high ice dam. At times, Glacial Lake Missoula extended some 200 miles eastward and grew to about half the size of modern-day Lake Michigan, containing about 500 cubic miles of water. Periodically, the ice dam failed. Floodwaters traveling at 65 miles an hour drained Glacial Lake Missoula in just 2-3 days, stripping away thick soils and cutting deep canyons in the underlying bedrock on its way to the Pacific Ocean. At the site of Bonneville Dam in the heart of the Columbia River Gorge, the raging torrent crested at 650 feet. During a period of 2,500 years as many as 100 of these floods scoured the Gorge.
The Cascade Mountains divide Oregon and Washington into very distinct western and eastern climate zones. Troutdale, Oregon, at the west entrance to the Gorge, has average annual precipitation of 44.9 inches. The Dalles, Oregon, at the east entrance to the Gorge, has just 14.5 inches. Troutdale is 5 degrees F warmer in winter and 5 degrees F cooler in summer than The Dalles. The distance between Troutdale and The Dalles is about 80 miles. At the west end of the Columbia River Gorge, one sees Douglas Fir trees, ferns, and lots of moss. At the east end of the Gorge, there are pine and oak trees, and grasses.
The photos below are posted in the order they were seen, traveling from west to east through the Columbia River Gorge. And now you can apply a basic understanding of the terrain and climate to the remarkable scenery and understand why it changes so much from start to finish.
Put your sandwich and beverage in the cooler and we'll have a picnic along the way...
Updated: 6:36 PM GMT on June 13, 2012
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