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Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. [1] In contrast, intrusive rock refers to rocks formed by magma which cools below the surface. [2]
Extrusive igneous rock is made from lava released by volcanoes Sample of basalt (an extrusive igneous rock), found in Massachusetts. Extrusive igneous rock, also known as volcanic rock, is formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, rapidly ...
Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. [9] [10] Intrusions must displace existing country rock to make room for ...
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Intrusion is one of the two ways igneous rock can form. The other is extrusion, such as a volcanic eruption or similar event. An intrusion is any body of intrusive igneous rock, formed from magma that cools and solidifies within the crust of the planet. In contrast, an extrusion consists of extrusive rock, formed above the surface of the crust.
Trap rock, also known as either trapp or trap, is any dark-colored, fine-grained, non-granitic intrusive or extrusive igneous rock. Types of trap rock include basalt, peridotite, diabase, and gabbro. [1] Trap is also used to refer to flood (plateau) basalts, such as the Deccan Traps and Siberian Traps. [2]
Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. [1]
When extrusive rocks make contact with the atmosphere they cool quickly, so the minerals do not have time to form large crystals. The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt, andesite, and rhyolite.