Search results
Results from the WOW.Com Content Network
Plutonism is the geologic theory that the igneous rocks forming the Earth originated from intrusive magmatic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again.
For example, andesitic magmatism is associated with the formation of island arcs at convergent plate boundaries while basaltic magmatism is found at mid-ocean ridges during sea-floor spreading at divergent plate boundaries. On Earth, magma forms by partial melting of silicate rocks either in the mantle, continental or oceanic crust. Evidence ...
Because of its low viscosity, this is the least explosive form of magma. Basaltic magma may found in regions such as Hawaii, known for its shield volcanoes. [1], [7] Basaltic magma forms minerals such as calcium-rich plagioclase feldspar and pyroxene. The water composition of basaltic magma varies dependent on the evolution of the magma chamber.
The average density of basalt is 2.9 g/cm 3, compared, for example, to granite’s typical density of 2.7 g/cm 3. [16] The viscosity of basaltic magma is relatively low—around 10 4 to 10 5 cP—similar to the viscosity of ketchup, but that is still several orders of magnitude higher than the viscosity of water, which is about 1 cP). [17]
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
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 ...
Magmatic underplating has been identified using multiple techniques that are non-specific to the area in which they are used. Geochemistry allows geologists to determine levels of association between igneous units: in the Karoo Province of southern Africa, large volumes of rhyolite along the continental margin were produced from melts with initially basaltic compositions.
2; the higher the silica content, the greater the ability of the magma to trap and hold on to gas and water vapor. When high-silica magma rises to the Earth's surface, the trapped gases and vapors can erupt explosively to produce ash clouds and pyroclastic flows that consist of superheated gas, ash and volcanic fragments.