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Crater Lake National Park is a United States National Park located in Southern Oregon whose primary feature is Crater Lake. It was established on May 22, 1902 as the fifth National Park in the U.S. The park encompasses Crater Lake's caldera, which rests in the remains of a destroyed volcano posthumously called Mount Mazama. The lake is 1,958 feet (597 m) deep at its deepest point, which makes it the deepest lake in the United States and the seventh deepest anywhere in the world. The caldera rim ranges in elevation from 7000 to 8000 feet (2100 to 2400 m). The average elevation of the lake itself is 6178 ft (1883 m). The park covers 286 mi² (741 km²). Crater Lake has no streams flowing into or out of it. The lake's water regularly has a striking blue hue.
Volcanic activity in the area is fed by subduction off the coast of Oregon as the Juan de Fuca Plate slips below the North American Plate (see plate tectonics). Heat and compression generated by this movement has created a mountain chain topped by a series of volcanoes, which together are called the Cascade Range. The large volcanoes in the range are called the High Cascades. However, there are many other volcanoes in the range as well, most of which are much smaller.
About 400,000 years ago, Mount Mazama began life in much the same way as the other mountains of the High Cascades, as overlapping shield volcanoes. Over time, alternating layers of lava flows and pyroclastic flows built Mazama's overlapping cones until it reached about 11000 feet (3400 m) in height.
As the young stratovolcano grew, many smaller volcanoes and volcanic vents were built in the area of the park and just outside what are now the park's borders. Chief among these were cinder cones. Although the early examples are gone—cinder cones erode easily—there are at least 13 much younger cinder cones in the park, and at least another 11 or so outside its borders, that still retain their distinctive cinder cone appearance. There continues to be debate as to whether these minor volcanoes and vents were parasitic to Mazama's magma chamber and system or if they were related to background Oregon Cascade volcanism.
After a period of dormancy, Mazama became active again. Then, around 4860 BC, Mazama collapsed into itself during a tremendous volcanic eruption, losing 2500 to 3500 feet (760 to 1100 m) in height. The eruption formed a large caldera that was later filled with a deep blue lake known today as Crater Lake.
The eruptive period that decapitated Mazama also laid waste to much of the greater Crater Lake area and deposited ash as far east as the northwest corner of what is now Yellowstone National Park, as far south as central Nevada, and as far north as southern British Columbia. It produced more than 150 times as much ash as the May 18, 1980 eruption of Mount St. Helens. Wikipedia |
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