2012年7月17日星期二

Lava Volvanoes

Lava Volvanoes is a type of molten rock expelled by a volcano during an eruption. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at temperatures from 700 °C to 1,200 °C (1,300 °F to 2,200 °F). Up to 100,000 times as viscous as water, lava can flow great distances before cooling and solidifying because of its thixotropic and shear thinning properties.

A lava flow is a moving outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. The term lava flow is commonly shortened to lava. Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word "lava" comes from Indonesia and Italian, and is probably derived from the Latin word labes which means a fall or slide.

Lava is molten rock that spews from an erupting volcano. It is extremely hot, reaching temperatures as high as 1,300 to 2,000 degrees Fahrenheit (704 to 1093 degrees Celsius). In a volcanic eruption, lava is in liquid form. When it solidifies, it forms igneous rock. However, it can take quite a long time to cool, traveling great distances before becomes solid. Molten rock is not always called lava. Before a volcano erupts and molten rock is still underground, it is called magma. Besides being a little cooler, molten rock is not dramatically different once it's above ground. The distinction between magma and lava is basically made to make geological occurrences easier to understand and explain.

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