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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 ...
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 ...
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; Dike – A sheet of rock that is formed in a fracture of a pre-existing rock body; Fissure vent – Linear volcanic vent through which lava erupts
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 ...
This glossary of geography terms is a list of definitions of terms and concepts used in geography and related fields, including Earth science, oceanography, cartography, and human geography, as well as those describing spatial dimension, topographical features, natural resources, and the collection, analysis, and visualization of geographic ...
Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings. [27] Cinder cones may form as flank vents on larger volcanoes, or occur on their own.
Vesicles are found towards the top of a pillow (because the gas trapped as part of the rock is less dense than its solid surroundings). The pillow structures show a convex (rounded) upper surface. The pillows might have a tapered base downwards, as they may have molded themselves to any underlying pillows during their formation.
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.