Volcano Type: Caldera
Volcano Status: Radiocarbon
Last Known Eruption: 2850 BC (?)
Summit Elevation: 2487 m 8,159 feet
Latitude: 42.93°N 42°56’0″N
Longitude: 122.12°W 122°7’0″W
The spectacular 8 x 10 km Crater Lake caldera in the southern Cascades of Oregon formed about 6850 years ago as a result of the collapse of a complex of overlapping shield and stratovolcanoes known as Mount Mazama. The cone-building stage, during which at least five andesitic and dacitic shields and stratovolcanoes were constructed, took place between about 420 and 40 thousand years ago (ka).
Sunrise at the Crater Lake
Crater Lake was formed around 4680 BC when the volcanic Mount Mazama blew its top in spectacular fashion. The eruption, estimated to have been 42 times more powerful than Mt. St. Helens’ 1980 blast, reduced Mazama’s approximate 11,000 foot height by around half a mile. The mountain peak feel into the volcano’s partially emptied neck and magma chamber, and Crater Lake was formed in the new crater.
Snow around the Crater Lake
Crater Lake has long been revered as sacred by the Klamath tribe of Native Americans, whose myths embody the catastrophic event they witnessed thousands of years ago. The central legend tells of two Chiefs, Llao of the Underworld and Skell of the World Above, pitted in a battle which ended in the destruction of Llao’s home, Mt. Mazama.
Crater Lake
A series of rhyodacitic lava domes and flows and associated pyroclastic rocks were erupted between about 30 ka and the climactic eruption. The explosive eruptions triggering collapse of the 8-10 km wide caldera about 7500 years ago were among Earth’s largest known Holocene eruptions, distributing tephra as far away as Canada and producing pyroclastic flows that traveled 40 km from the volcano. A 5-km-wide ring fracture zone is thought to mark the original collapse diameter. The deep blue waters of North America’s second deepest lake, at 600 m, fill the caldera to within 150-600 m of its rim. Post-caldera eruptions within a few hundred years of caldera formation constructed a series of small lava domes on the caldera floor, including the partially subaerial Wizard Island cinder cone, and the completely submerged Merriam Cone. The latest eruptions produced a small rhyodacitic lava dome beneath the lake surface east of Wizard Island about 4200 years ago.
Originally posted 2010-08-17 05:24:55.
