The portion of the mantle that lies at a depth of 100 to 350 km below the surface. Rocks in the asthenosphere are ductile and easily deformed.

Basin and Range

An area of the southwestern United States characterized by roughly parallel mountain ranges and valleys.brittleA brittle material fractures when it deforms.


A rock fragment produced by the mechanical breakdown of older rocks.

continental crust

The part of Earthàs crust that includes and underlies the continents and continental shelves. The continental crust averages about 40 km thick.


The outermost and thinnest of the solid Earthàs 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.deformationWhen rock changes shape.


The act of laying down rock-forming matter (sediment) by a natural process, such as wind, water, or ice.ductileA ductile material can deform without fracturing.


When Earth's lithosphere stretches.


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


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


The study of Earth's physical positioning system (GPS)A system of satellites, computers, and receivers that can determine the location (latitude and longitude) of a receiver on Earth.


The outer layer of solid rock that includes the crust and uppermost mantle. This layer, up to 100 km thick, forms Earth's tectonic plates.


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


A solid substance with a crystal structure that formed via geologic processes. Minerals can be either elements or compounds.


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


One of several large, interlocking, mobile pieces of Earth's lithosphere.

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.


A geological region that shares distinct characteristics.sedimentUnconsolidated 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.


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