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Volcanic rocks and sediment that form from magma erupted into the air are called "pyroclastics," and these are also technically sedimentary rocks. Volcanic rocks are among the most common rock types on Earth's surface, particularly in the oceans.
Trachybasalt – Volcanic rock – A volcanic rock with a composition between basalt and trachyte 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
Beach pebble of variolitic pillow lava (varolite) from the Olympic Peninsula, Washington stateVariolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called varioles, in a fine-grained matrix.
The volcanic rock resulting from subsequent cooling is often also called lava. A lava flow is an outpouring of lava during an effusive eruption . (An explosive eruption , by contrast, produces a mixture of volcanic ash and other fragments called tephra , not lava flows.)
A pyroclastic rock containing 25–75% volcanic bombs and/or volcanic blocks is called tuff breccia. [4] Tuff composed of sandy volcanic material can be referred to as volcanic sandstone. [5] Tuff is a relatively soft rock, so it has been used for construction since ancient times. [6]
Basalt is also the principal volcanic rock in many oceanic islands, including the islands of HawaiĘ»i, [35] the Faroe Islands, [83] and Réunion. [84] The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. [85] Paraná Traps, Brazil. Basalt is the rock most typical of large igneous provinces.
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.
Volcanic lightning is an electrical discharge triggered by a volcanic eruption, not a typical thunderstorm. It forms when ash particles collide and fragment, generating static electricity within ...