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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 ...
Complex volcano – Landform of more than one related volcanic centre; Cryptodome – Roughly circular protrusion from slowly extruded viscous volcanic lava; Cryovolcano – Type of volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock; Diatreme – Volcanic pipe associated with a gaseous explosion
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. For these ...
In some cases, a lava plateau may be part of a single volcano. An example is the massive Level Mountain shield volcano in northern British Columbia, Canada, which covers an area of 1,800 km 2 (690 sq mi) and a volume of 860 km 3 (210 cu mi). [1]
A unit of area traditionally defined as the area of a plot of land one chain (66 feet) by one furlong (660 feet), equivalent to 43,560 square feet (0.001563 sq mi; 4,047 m 2), or about 0.40 hectare. active volcano A volcano that is currently erupting, or one that has erupted within the last 10,000 years (the Holocene) or during recorded history ...
For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. [14]
The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
The magma ascends to form an arc of volcanoes parallel to the subduction zone. Volcanic arcs are distinct from volcanic chains formed over hotspots in the middle of a tectonic plate. Volcanoes often form one after another as the plate moves over the hotspot, and so the volcanoes progress in age from one end of the chain to the other.