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Volcanic rock. 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.
volcanic plateaus. Upper Table Rock and Lower Table Rock are two prominent volcanic plateaus located just north of the Rogue River in Jackson County, Oregon, U.S. Created by an andesitic lava flow approximately seven million years ago and shaped by erosion, they now stand about 800 feet (240 m) above the surrounding Rogue Valley.
Basalt columns seen on Porto Santo Island, Portugal. Columnar jointing of volcanic rocks exists in many places on Earth. Perhaps the most famous basalt lava flow in the world is the Giant's Causeway in Northern Ireland, in which the vertical joints form polygonal columns and give the impression of having been artificially constructed.
Basalt (UK: / ˈbæsɔːlt, - əlt /; [1] US: / bəˈsɔːlt, ˈbeɪsɔːlt /) [2] is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low- viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt.
The geology of the Canary Islands is dominated by volcanoes and volcanic rock. The Canary Islands are a group of volcanic islands in the North Atlantic Ocean, near the coast of Northwest Africa. The main islands are Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma, and El Hierro. [Note 1] There are also some minor islands ...
Pyroclastic plateaus are produced by massive pyroclastic flows. They are underlain by pyroclastic rocks: agglomerates, tephra, volcanic ashes cemented into tuffs, mafic or felsic. Pyroclastic plateaus are also called ignimbrite plateaus. Examples include the Shirasu-Daichi, which makes up almost all of southern Kyūshū, Japan, [3] and the ...
The average composition of felsic volcanic rocks in Archean greenstone belts is between dacite and rhyolite (Table 2). [ 3 ] [ 6 ] In comparison, the modern felsic volcanic rock average composition (after Archean, <2.5 Ga) is similar to rhyolite, indicating a more felsic shift with greater alkali content in felsic volcanism. [ 6 ]
Scoria. Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts. [1][2] It is typically dark in color (brown, black or purplish-red), and basaltic or andesitic in composition. Scoria has relatively low density, as it is ...