A caldera lake is formed in several stages following a cataclysmic volcanic eruption.
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| Crater Lake is a lake that was formed in a caldera from precipitation and snow melt. |
Cataclysmic Eruption
During a cataclysmic eruption (below), a fast-moving column of ash, hot gas, and rock escapes from a subsurface magma chamber blasting up through the ground surface and spewing into the atmosphere. As subsurface materials are transported and displaced to the surface, the volume of the magma chamber decreases.
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| Cataclysmic Eruption |
Caldera Collapse
The volcano and land mass above a magma chamber is supported, in part, by the magma itself. As a significant volume of magmatic material is displaced by the eruption, a volcanic summit forms. Vertical fissures formed beneath the summit (below) advance the collapse and subsidence of the displaced volume of erupted material. A conical ring of pumice and ash surround the collapsed summit.
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| Caldera Collapse |
New Caldera
After the ash settles, and the magmatic system finds a new isostatic equilibrium, the remaining surface depression is the newly formed caldera. In the depiction below, ground water interacts with hot deposits causing eruptions of steam.
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| New Caldera |
Caldera Lake
The depression fills with precipitation to become a lake (below). Over time, renewed eruptions from vents in the caldera might form an island in the lake. Wizard Island is a cinder cone that formed an island in Crater Lake.
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| Caldera Lake |
REFERENCES
- Caldera, Wikipedia.
- Crater Lake, Wikipedia.
- Crater Lake, Oregon, Wikipedia.
- Pyroclastic Flow, Wikipedia.
- 42 of the World’s Most Beautiful Crater Lakes.
- Some fundamentals about Crater Lakes.
- The Science of Volcanic Lakes, by Greg Pasternack, 1996.
