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Cool Facts About Lava For Kids

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. 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.
  • Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows.
  • Serao described “a flow of fiery lava” as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain.
  • Igneous rocks, which form lava flows when erupted, can be classified into three chemical types; felsic, intermediate, and mafic.
  • These classes are primarily chemical; however, the chemistry of lava also tends to correlate with the magma temperature, its viscosity and its mode of eruption.
  • Felsic lava Felsic lavas such as rhyolite and dacite typically form lava spines, lava domes or “coulees” and are associated with pyroclastic (fragmental) deposits.
  • The high viscosity and strength are the result of their chemistry, which is high in silica, aluminium, potassium, sodium, and calcium, forming a polymerized liquid rich in feldspar and quartz, which thus has a higher viscosity than other magma types.
  • Felsic magmas can erupt at temperatures as low as 650 to 750 °C.
  • Basalt lavas tend to produce low-profile shield volcanoes or “flood basalt fields”, because the fluidal lava flows for long distances from the vent.
  • Ultramafic lava Ultramafic lavas such as komatiite and highly magnesian magmas which form boninite take the composition and temperatures of eruptions to the extreme.
  • Lavas with high viscosity are rhyolite, dacite, andesite and trachyte, with cooled basaltic lava also quite viscous; those with low viscosities are freshly erupted basalt, carbonatite and occasionally andesite.
  • Highly viscous lava shows the following behaviors: tends to flow slowly, clog, and form semi-solid blocks which resist flow tends to entrap gas, which form vesicles (bubbles) within the rock as they rise to the surface correlates with explosive or phreatic eruptions and is associated with tuff and pyroclastic flows Highly viscous lavas do not usually flow as liquid, and usually form explosive fragmental ash or tephra deposits.
  • The ideal lava flow will have a brecciated top, either as pillow lava development, autobreccia and rubble typical of ʻaʻā and viscous flows, or a vesicular or frothy carapace such as scoria or pumice.
  • They range in shape from shield volcanoes with broad, shallow slopes formed from predominantly effusive eruptions of relatively fluid basaltic lava flows, to steeply-sided stratovolcanoes made of alternating layers of ash and more viscous lava flows typical of intermediate and felsic lavas.
  • A caldera, which is a large subsidence crater, can form in a stratovolcano, if the magma chamber is partially or wholly emptied by large explosive eruptions; the summit cone no longer supports itself and thus collapses in on itself afterwards.
  • Lava tubes are formed when a flow of relatively fluid lava cools on the upper surface sufficiently to form a crust.
  • The term “lava” can also be used to refer to molten “ice mixtures” in eruptions on the icy satellites of the Solar System’s gas giants.