Lava lakes form when molten lava, typically basaltic, partially fills a volcanic crater, vent, or a broad depression within a shield volcano's summit caldera.
Formation Mechanisms:
Several processes can lead to the formation of lava lakes:
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Persistent Eruption: A continuous or near-continuous eruption from a vent can supply enough lava to fill a crater or depression. This is the most common formation mechanism.
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Vent Obstruction: If a volcanic vent becomes partially blocked or constricted, molten lava can accumulate within the vent itself or in the surrounding crater.
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Caldera Collapse: Following a major eruption that empties a magma chamber, the roof of the chamber can collapse, creating a large depression (caldera). If subsequent eruptions occur within the caldera, a lava lake can form.
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Drainage Failure: Sometimes, lava flows may pond in depressions if they are unable to drain away efficiently, leading to the formation of localized lava lakes.
Characteristics of Lava Lakes:
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Composition: Most lava lakes are composed of basaltic lava, which is relatively fluid and low in silica. However, some lava lakes can consist of other lava types as well.
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Crusting and Circulation: The surface of a lava lake typically cools and forms a crust. This crust can break up and sink back into the molten lava, leading to constant circulation and mixing.
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Gas Release: Lava lakes often release significant amounts of volcanic gases, such as sulfur dioxide and carbon dioxide.
Examples of Lava Lakes:
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Mount Nyiragongo (Democratic Republic of Congo): Famous for its large and active lava lake.
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Erta Ale (Ethiopia): Hosts a long-lived lava lake in its summit crater.
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Kilauea (Hawaii): Before the 2018 eruption, Kilauea had a lava lake within the Halemaʻumaʻu crater.
In summary, lava lakes are dynamic features formed when molten lava accumulates in a volcanic depression, typically due to continuous eruptions, vent obstruction, caldera collapse, or drainage failures.
