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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 ...
Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks .
Ignimbrite is a type of volcanic rock, consisting of hardened tuff. [1] Ignimbrites form from the deposits of pyroclastic flows , which are a hot suspension of particles and gases flowing rapidly from a volcano , driven by being denser than the surrounding atmosphere.
Hawaiite – Volcanic rock – a sodic type of trachybasalt, typically formed by ocean island volcanism; 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
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. Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass ...
File:Shoshonite lava flows on South Table Mountain, Colorado. Shoshonite is a type of igneous rock.More specifically, it is a potassium-rich variety of basaltic trachyandesite, [1] composed of olivine, augite and plagioclase phenocrysts in a groundmass with calcic plagioclase and sanidine and some dark-colored volcanic glass.
A magmatic dike is a sheet of igneous rock that cuts across older rock beds. It is formed when magma fills a fracture in the older beds and then cools and solidifies. [2] [3] [4] The dike rock is usually more resistant to weathering than the surrounding rock, so that erosion exposes the dike as a natural wall or ridge. [3]
IUGS classification of aphanitic extrusive igneous rocks according to their relative alkali (Na 2 O + K 2 O) and silica (SiO 2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot. [1] An aphanitic volcanic sand grain, with fine-grained groundmass, as seen through a petrographic microscope