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Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C (1,470 to 2,190 °F). The volcanic rock resulting from subsequent cooling is also often called lava. A lava flow is an outpouring of lava during an effusive eruption.
When erupted, the temperature of the molten iron oxide magma is about 700 to 800 °C (1,292 to 1,472 °F). [42] Sulfur lava flows up to 250 metres (820 feet) long and 10 metres (33 feet) wide occur at Lastarria volcano, Chile. They were formed by the melting of sulfur deposits at temperatures as low as 113 °C (235 °F). [16]
The temperature of a Pāhoehoe lava flow can be estimated by observing its color. The result agrees well with other measurements of temperatures of lava flows at about 1,000 to 1,200 °C (1,830 to 2,190 °F). When the body is black, the absorption is obvious: the amount of light absorbed is all the light that hits the surface.
Low viscosity lava can generate massive lava fountains, while lava of thicker viscosity can solidify within the vent, creating a volcanic plug. Volcanic plugs can trap volcanic gas and create pressure in the magma chamber, resulting in violent eruptions. [36] Lava is typically between 700 and 1,200 °C (1,300–2,200 °F). [37]
The behaviour of lava depends upon its viscosity, which is determined by temperature, composition, and crystal content. High-temperature magma, most of which is basaltic in composition, behaves in a manner similar to thick oil and, as it cools, treacle. Long, thin basalt flows with pahoehoe surfaces are common.
Molten rock (either magma or lava) near the atmosphere releases high-temperature volcanic gas (>400 °C). In explosive volcanic eruptions, the sudden release of gases from magma may cause rapid movements of the molten rock. When the magma encounters water, seawater, lake water or groundwater, it can be rapidly fragmented.
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Ultramafic lava may have been detected on Io, a moon of Jupiter, because heat-mapping of Io's surface found ultra-hot areas with temperatures in excess of 1,200 °C (2,190 °F). The magma immediately below these hot spots is probably about 200 °C (360 °F) hotter, based on surface-to-subsurface temperature differences observed for lava on Earth.