November 25, 2002
Among the largest volcanic eruptions on Earth are the flood basalts. They erupt from long fissures in the ground and have spewed out thousands of cubic miles of lava over hundreds of thousands of years. The basalt that forms Hat Rock in northern Oregon (pictured above) is the result of one of these eruptions that occurred in the American northwest from 16 million to 12 million years ago. Covering much of eastern Washington and Oregon, these Columbia River Basalts were subsequently eroded by epic floods, the Pleistocene Missoula Floods. These floods started in what is present day Montana when glacial Lake Missoula catastrophically drained. At their peak, these floodwaters had a larger volume than all the world's rivers combined. These raging torrents sculpted Hat Rock into its unique shape. Lewis and Clark passed Hat Rock as they paddled down the Columbia to the Oregon coast in 1805. Hat Rock is located north of Pendleton, Oregon, near the Columbia River.