Crater Lake

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For the general term of a geological feature that goes by the same name, see crater lake.

Crater Lake is a lake in the U.S. state of Oregon that is 5 by 6 miles (8 by 9.6 km) and 1958 ft (597 m) deep. It is Crater Lake National Park's most prominent feature and is famous for its deep blue color, water clarity and vertical driftwood, named Old Man of the Lake. Crater Lake is one of Oregon's four National Parks (Lewis and Clark National Historical Park, Oregon Caves National Monument, and John Day Fossil Beds National Monument being the others). The lake partly fills a nearly 4000 ft (1220 m) deep caldera that was formed around 6900 years ago by the collapse of the volcano Mount Mazama.

The lake's average depth is 1,148 ft (350 m). Its deepest point has been measured at 1949 ft (594 m) deep though as with any lake its depth fluctuates with the climate, particularly rainfall [http://soundwaves.usgs.gov/2000/09/fieldwork.html. This makes Crater Lake the deepest lake in the United States, the second deepest lake in the Western Hemisphere (Great Slave Lake is deepest) and the seventh deepest lake in the world (Lake Baikal is deepest). It also holds the honor of being the deepest lake in the world that is completely above sea level. The caldera rim ranges in elevation from 7000 to 8000 ft (2130 to 2440 m). The average elevation of the lake's surface is 6178 ft (1883 m).

The Oregon state quarter, released in 2005, features an image of Crater Lake.

Geology

The caldera was created in a massive volcanic eruption that lead to the subsidence of Mount Mazama around 4860 BC. Since that time, all eruptions on Mazama have been confined to the caldera.

Lava eruptions later created a central platform, Wizard Island, Merriam Cone, and other, smaller volcanic features, including a rhyodacite dome that was eventually created atop the central platform. Sediments and landslide debris also covered the caldera floor.

In time, the caldera cooled, allowing rain and snow to accumulate and eventually form a lake. Landslides from the caldera rim thereafter formed debris fans and turbidite sediments on the lakebed. Fumaroles and hot springs remained common and active during this time.

In time, the slopes of the caldera rim more or less stabilized, streams restored a radial drainage pattern on the mountain, and dense forests revegetated the barren landscape.

Some hydrothermal activity remains at the lake floor, suggesting that someday in the future Mazama may erupt again. ^*

Water quality

Due to several factors, most prominently that it has no inlets or tributaries, the waters of Crater Lake are some of the purest in terms of the absence of pollutants in North America.

Secchi disk clarity readings have consistently been in the high-20m to mid-30m range, which is very clear for any natural body of water. In 1997, scientists recorded a record clarity of 43.3 meters (142 ft). The lake traditionally has relatively high levels of dissolved salts, total alkalinity, and conductivity. The average pH has generally ranged between 7 and 8.

References

Fire Mountains of the West: The Cascade and Mono Lake Volcanoes, Stephen L. Harris, (Mountain Press Publishing Company, Missoula; 1988) ISBN 0-87842-220-X
Geology of National Parks: Fifth Edition, Ann G. Harris, Esther Tuttle, Sherwood D., Tuttle (Iowa, Kendall/Hunt Publishing; 1997) ISBN 0-7872-5353-7

External links

Crater Lake | Kratersko jezero, ZDA

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Geology

Water quality

References

See also

External links