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Shield volcanoes are large, slow forming volcanoes [6] that erupt fluid basaltic magma that cools to form the extrusive rock basalt.Basalt is composed of minerals readily available in the planet's crust, including feldspars and pyroxenes.
In 1992, Coffin and Eldholm initially defined the term "large igneous province" as representing a variety of mafic igneous provinces with areal extent greater than 100,000 km 2 that represented "massive crustal emplacements of predominantly mafic (magnesium- and iron-rich) extrusive and intrusive rock, and originated via processes other than 'normal' seafloor spreading."
However, extrusion at mid-ocean ridges is relatively steady, while extrusion of flood basalts is highly episodic. Flood basalts create new continental crust at a rate of 0.1 to 8 cubic kilometers (0.02 to 2 cu mi) per year, while the eruptions that form oceanic plateaus produce 2 to 20 cubic kilometers (0.5 to 5 cu mi) of crust per year.
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one meter in diameter.
Vesicular texture in volcanic rock from Tenerife Vesicular olivine basalt from La Palma. Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities (known as vesicles) at its surface and inside.
In geology, an igneous intrusion (or intrusive body [1] or simply intrusion [2]) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth.
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section.
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 ...