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The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
Shallow intrusions, which possess structure similar to volcanic rather than plutonic rocks, are also considered to be volcanic, shading into subvolcanic. [citation needed] The terms lava stone and lava rock are more used by marketers than geologists, who would likely say "volcanic rock" (because lava is a molten liquid and rock is solid).
The change of rock composition most responsible for the creation of magma is the addition of water. Water lowers the solidus temperature of rocks at a given pressure. For example, at a depth of about 100 kilometers, peridotite begins to melt near 800 °C in the presence of excess water, but near 1,500 °C in the absence of water. [69]
Igneous rock (igneous from Latin igneus 'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.
Once initially established, continued lava flow creates a steeper upstream face as it battles the rising water, but with most lava flowing unimpeded downstream covering the now-dried river bed and its alluvial sediments, sometimes for miles. Thus emplaced, the shape of a lava dam resembles an elongated blob, wedged in the valley bottom.
The use of rock has had a huge impact on the cultural and technological development of the human race. Rock has been used by humans and other hominids for at least 2.5 million years. [22] Lithic technology marks some of the oldest and continuously used technologies. The mining of rock for its metal content has been one of the most important ...
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.
Pahoehoe lava is a relatively smooth lava flow that can be billowy or ropey. They can move as one sheet, by the advancement of "toes", or as a snaking lava column. [10] A'a lava flows are denser and more viscous than pahoehoe, and tend to move slower. Flows can measure 2 to 20 m (7 to 66 ft) thick.