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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 ...
Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks and they are usually much finer-grained, often resembling volcanic rock. [8] Hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths , or phacoliths .
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 ...
English: Intrusive and extrusive rock formation. Extrusions result in lava flows, while intrusions cool and form igneous rock beneath the surface. Extrusions result in lava flows, while intrusions cool and form igneous rock beneath the surface.
Trachyte – Extrusive igneous rock – A silica-undersaturated volcanic rock; essentially a feldspathoid-bearing rhyolite; Troctolite – Igneous rock – A plutonic ultramafic rock containing olivine, pyroxene and plagioclase; Trondhjemite – Light-colored intrusive igneous rock – A form of tonalite where plagioclase-group feldspar is ...
Half Dome, a quartz monzonite monolith in Yosemite National Park and part of the Sierra Nevada Batholith. A batholith (from Ancient Greek bathos 'depth' and lithos 'rock') is a large mass of intrusive igneous rock (also called plutonic rock), larger than 100 km 2 (40 sq mi) in area, [1] that forms from cooled magma deep in the Earth's crust.
In geology, a chonolith is a type of igneous rock intrusion (also known as pluton). Igneous rock intrusions are bodies of igneous rock that are formed by the crystallization of cooled magma below the Earth’s surface. These formations are termed intrusive rocks due the magma intruding rock layers but never reaching the surface. [1]
Shonkinite is an intrusive igneous rock.More specifically, it is a mafic foidal (feldspathoid bearing) syenite, a holocrystalline (completely crystalline) intrusive rock which, in the restricted sense [clarify], is composed of potassic feldspar (in the form of sanidine), with nepheline, augite, biotite, and olivine. [1]