A term to describe a volcano that is currently erupting.
A form of stress produced by the action of equal and opposite forces, the effect of which is to reduce the length of a material. Compression is a form of pressure.
A tectonic process whereby plates move toward each other.
The uppermost division of the solid earth, representing less than 1% of its volume and varying in depth from 3 mi. to 37 mi. (5-60 km). Below the crust is the mantle.
A tectonic process whereby plates move away from each other.
A term to describe a volcano that is not currently erupting but is likely to do so in the future.
One of two principal forms of tectonism, the other beingorogenesis. Derived from the Greek words epeiros ("mainland") and genesis ("origins"), epeirogenesis takes the form of either uplift or subsidence.
A term to describe a volcano for which no eruption has been known in recorded history. In this case, it is likely that the volcano has ceased to erupt permanently.
An area of physical geology concerned with the study of landforms, with the forces and processes that have shaped them, and with the description and classification of various physical features on Earth.
A region of high volcanic activity.
A notable topographicalfeature, such as a mountain, plateau, or valley.
The upper layer of Earth's interior, including the crust and the brittle portion at the top of the mantle.
The thick, dense layer of rock, approximately 1,429 mi. (2,300 km) thick, between Earth's crust and its core.
Structure or form or the study thereof.
A series of ranges stretching across a continent for a greatdistance.
An irregular grouping of mountains, which lacks the broad linear sweep of a range or chain.
A relatively localized series of peaks and ridges.
A combination of ranges, chains, and masses of mountains that stretches across vast distances, usually encompassing more than one continent.
A Greek word meaning "mountain," which appears in such words as orogeny, a variant of orogenesis; orogen, another term for "mountain" and orogenic, as in "orogenic belt."
One of two principal forms of tectonism, the other being epeiro-genesis. Derived from the Greek words oros ("mountain") and genesis ("origin"), oro-genesis involves the formation of mountain ranges by means of folding, faulting, and volcanic activity. The processes of oro-genesis play a major role in plate tectonics.
Boundaries between plates.
The name both of a theory and of a specialization of tectonics. As an area of study, plate tectonics deals with the large features of the lithosphere and the forces that shape them. As atheory, it explains the processes that have shaped Earth in terms of plates and their movement.
Large, movable segments of the lithosphere.
A form of stress resulting from equal and opposite forces that do not act along the same line. If a thick, hard-bound book is lying flat, and one pushes the front cover from the side so that the covers and pages are no longer aligned, this is an example of shear.
The ratio between the change in dimension experienced by an object that has been subjected to stress and the original dimensions of the object.
In general terms, any attempt to deform a solid. Types of stress includetension, compression, and shear.
A term that refers either to the process of subsiding, on the part of air or solid earth, or, in the case of solid earth, to the resulting formation. Subsidence thus is defined variously as the downward movement of air, the sinking of ground, or a depression in Earth's crust.
The study of tectonism, including its causes and effects, most notably mountain building.
The deformation of the lithosphere.
A form of stress produced by a force that acts to stretch a material.
The configuration of Earth's surface, including its relief as well as the position of physical features.
A process whereby the surface of Earth rises, as the result of either a decrease in downward force or an increase in upward force.
A natural opening in Earth's surface through which molten (liquid), solid, and gaseous material erupts. The word volcano is also used to describe the cone of erupted material that builds up around the opening or fissure.
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