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Magma that cools slowly within a magma chamber usually ends up forming bodies of plutonic rocks such as gabbro, diorite and granite, depending upon the composition of the magma. Alternatively, if the magma is erupted it forms volcanic rocks such as basalt , andesite and rhyolite (the extrusive equivalents of gabbro, diorite and granite ...
Intermediate composition magma, such as andesite, tends to form cinder cones of intermingled ash, tuff and lava, and may have a viscosity similar to thick, cold molasses or even rubber when erupted. Felsic magma, such as rhyolite, is usually erupted at low temperature and is up to 10,000 times as viscous as basalt. Volcanoes with rhyolitic ...
Cumulate rock – Igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Flow banding – Bands or layers that can sometimes be seen in rock that formed from magma; Fractional crystallization (chemistry) – Method for refining substances based on differences in their solubility
The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about 20–25 cubic kilometres per year (4.8–6.0 cu mi/a). Global magma production rates on Earth are about 20–25 cubic kilometres per year (4.8–6.0 cu mi/a).
Igneous rocks have crystallised from a melt or magma. The melt is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. The melt is hot and so passes upward through cooler country rock.
Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained . However, the rate of cooling is greatest for intrusions at relatively shallow depth, and the rock in such intrusions is often much less coarse-grained than intrusive rock ...
Over half the original magma remains in the lower crust as cumulates in a system of dikes and sills. [34] [21] As the magma rises, the drop in pressure also lowers the liquidus, the temperature at which the magma is fully liquid. This likely explains the lack of phenocrysts in erupted flood basalt.
Finally, the continuous drop in pressure and temperature in 1800 Ma resulted from further erosion and exhumation. The peak pressure is found to be reached before the peak temperature, owing to the relatively poor thermal conductivity of the rock upon increasing P-T condition, while the rock instantaneously experienced the pressure changes.