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The outermost and thinnest of the solid Earth’s layers, which consists of rocky material that is less dense than the rocks of the mantle below.


Information, often in the form of measurements or observations, which can be analyzed.


When rock changes shape.


The act of laying down rock-forming matter (sediment) by a natural process, such as wind, water, or ice.


The height of an object above a particular reference level, usually sea level.


A rock fracture or fracture zone along which there has been movement.

geologic time

The period of time covering the physical formation and development of Earth, as recorded within the succession of rocks.


The study of Earth, its history, its composition, its structure, and the dynamic processes that shape it.


A permanent body of ice that shows evidence of downslope or outward movement due to the stress of its own weight.


The study of glaciers.


A massive chunk of glacier ice floating in water or stranded on a shore.kilometer (km)A unit of length equal to 1,000 meters, or 0.62 miles.


Imaginary horizontal lines that allow the measurement of a position north or south of the equator. Latitude is measured in degrees (at the equator, one degree = 60 nautical miles, or 111 kilometers). The equator is at a latitude of 0° and the poles lie at latitudes of 90° north (North Pole) and 90° south (South Pole). Because of Earth’s oblateness, a degree of latitude near the polar regions is about 112 km in length. Because of Earth’s oblateness, a degree latitude near the polar regions is about 112 km in length.


The layer within Earth that lies between the crust and the core.


A unit of length in the metric system equal to 3.28 feet.


A theoretical system that represents scientific processes using a set of variables and the quantitative relationships between them.

plate tectonics

The theory and study of plate formation, movement, interaction and destruction; the attempt to explain seismicity, volcanism, mountain-building, and paleomagnetic evidence in terms of plate motions.polarRelating to or located near the North Pole or South Pole.


Unconsolidated particles, ranging from clay-size to boulders, produced by the breakdown of rocks that may be carried by natural agents (wind, water, and ice) and eventually deposited to form sedimentary deposits. Organisms and chemical precipitation can also produce sediment.


The study of earthquakes and other seismic waves.

subduction zone

The zone of convergence of two tectonic plates, one of which usually overrides the other.


Relating to the forces and the movements of Earth and its lithosphere. Earthquakes, volcanoes, and mountain building are related to tectonic activity.

tectonic plate

One of several large, mobile pieces of Earth’s lithosphere adjoining other plates along zones of seismic activity.


The outer, lower margin of a glacier.terraneA fragment of crust broken off of one tectonic plate and attached to the crust on another plate.


The surface elevation of land and its variations.


The process or result of raising a portion of Earth’s crust through tectonic mechanisms.