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Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones ...
Volcanic explosivity index. The Volcanic Explosivity Index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982. Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle ...
t. e. The epicenter (/ ˈɛpɪˌsɛntər /), epicentre, or epicentrum[1] in seismology is the point on the Earth 's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates.
Volcaniclastics are geologic materials composed of broken fragments (clasts) of volcanic rock. [1] These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it was deposited in, or whether nonvolcanic material is mingled with the volcanic clasts. [2]
In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent.
Volcanism. Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. [1] It is caused by the presence of a heat source, usually internally generated, inside the body; the heat is generated by ...
Volcanic hazard. A schematic diagram shows some of the many ways volcanoes can cause problems for those nearby. A volcanic hazard is the probability a volcanic eruption or related geophysical event will occur in a given geographic area and within a specified window of time. The risk that can be associated with a volcanic hazard depends on the ...
A volcanic arc is part of an arc-trench complex, which is the part of a subduction zone that is visible at the Earth's surface. A subduction zone is where a tectonic plate composed of relatively thin, dense oceanic lithosphere sinks into the Earth's mantle beneath a less dense overriding plate.