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Crater Lake |
During the few centuries preceding the last, climactic eruption, at least two large eruptions of rhyolite occurred in the area underlain by the magma chamber. Tephra from one of these eruptions extended into eastern Washington and western Nevada. The climactic eruption of Mt. Mazama occured 6850 yrs ago, and took place over a number of months. The eruptions produced tephra-fall and two episodes of pyroclastic-flow deposits. Tephra deposits from this series of eruptions have been found in 8 western states and 3 Canadian provinces. The major episode of pyroclastic-flow in this series of eruptions extended to 60 km (40 miles). Following this series of eruptions, the caldera finally collapsed into the magma chamber, and Mt Mazama became dormant except for activity which formed a small cinder cone in the center. The collapsed caldera filled with water and became what we now know as Crater Lake. The total volume of magma erupted during the climactic eruption was about 10 times larger than that produced during any other explosive eruption in the Cascade Range during postglacial times. The Yakima People who lived near Mt. Mazama when it fell have a different story of what caused the mountain to collapse. |
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During the few centuries preceding the last, climactic eruption, at least two other large eruptions occurred. Ash and pumice from one of these eruptions extended into eastern Washington and western Nevada. The last climactic eruption of Mt. Mazama occured 6850 years ago, over a number of months, and produced major outbursts of ash, lava, and hot vapors. Deposits from this series of eruptions have been found in 8 western states and 3 Canadian provinces. Following the final series of eruptions, the cone of the volcano collapsed into the magma chamber, and Mt Mazama became dormant except for activity which formed a small cinder cone in the center (shown in this picture). The collapsed volcano filled with water and became what we now know as Crater Lake. The Yakima Indians who lived near Mt. Mazama when it collapsed have a different story of what caused the mountain to fall. |
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6850 years ago, Mt. Mazama erupted for a final time. The eruption occured over a number of months, and produced major outbursts of ash, lava, and hot vapors. Following this series of eruptions, the cone of the volcano collapsed into the ground, and Mt Mazama became dormant except for activity which formed a small cinder cone in the center (shown in this picture). The collapsed volcano filled with water and became what we now know as Crater Lake. The Indians who lived near Mt. Mazama when it fell have a different story of what caused the mountain to collapse. |
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