Earth's Interior - Key terms



ASTHENOSPHERE:

A region of extremely high pressure underlying the lithosphere, where rocks are deformed by enormous stresses. The asthenosphere liesat a depth of about 60 mi. to 215 mi.(about 100-350 km).

ATMOSPHERE:

In general, an atmosphere is a blanket of gases surrounding a planet. Unless otherwise identified, however, the term refers to the atmosphere of Earth, which consists of nitrogen (78%), oxygen (21%), argon (0.93%), and other substances that include water vapor, carbon dioxide, ozone, and noble gases such as neon (0.07%).

CORE:

The center of Earth, an area constituting about 16% of the planet's volume and 32% of its mass. Made primarily of iron and another, lighter element (possibly sulfur), it is divided between a solid inner core with a radius of about 760 mi.(1,220 km) and a liquid outer core about1,750 mi. (2,820 km) thick. For terrestrial planets, in general, core refers to the center, which in most cases is probably molten metal of some kind.

CRUST:

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.

GEOCHEMISTRY:

A branch of the earth sciences, combining aspects of geology and chemistry, that is concerned with the chemical properties and processes of Earth—in particular, the abundance and interaction of chemical elements and their isotopes.

GEOLOGY:

The study of the solid earth, in particular, its rocks, minerals, fossils, and land formations.

GEOPHYSICS:

A branch of the earth sciences that combines aspects of geology and physics. Geophysics addresses the planet's physical processes as well as its gravitational, magnetic, and electric properties and the means by which energy is transmitted through its interior.

GEOSPHERE:

The upper part of Earth's continental crust, or that portion of the solid earth on which human beings live and which provides them with most of their food and natural resources.

JOVIAN PLANETS:

The planets between Mars (the last terrestrial planet) and Pluto, all of which are large, low indensity, and composed primarily of gases.

LITHOSPHERE:

The upper layer of Earth's interior, including the crust and the brittle portion at the top of the mantle.

MANTLE:

The thick, dense layer of rock, approximately 1,429 mi. (2,300 km) thick, between Earth's crust and its core. In reference to the other terrestrial planets, mantle simply means the area of dense rock between the crust and core.

ORGANIC:

At one time chemists used the term organic only in reference to living things. Now the word is applied to most compounds containing carbon, with the exception of carbonates (which are minerals) and oxides, such as carbon dioxide.

PLATE TECTONICS:

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. Plate tectonics theory brings together aspects of continental drift, seafloor spreading, seismic and volcanic activity, and the structures of Earth's crust to provide a unifying model of Earth's evolution. It is one of the dominant concepts in the modern earth sciences.

PLATES:

Large, movable segments of the lithosphere.

SEISMIC WAVE:

A packet of energy resulting from the disturbance that accompanies a strain on rocks in the lithosphere.

SEISMOLOGY:

The study of seismic waves as well as the movements and vibrations that produce them.

TECTONICS:

The study of tectonism, including its causes and effects, most notably mountain building.

TECTONISM:

The deformation of the lithosphere.

TERRESTRIAL PLANETS:

The four inner planets of the solar system: Mercury, Venus, Earth, and Mars. These are all small, rocky, and dense; have relatively small amounts of gaseous elements; and are composed primarily of metals and silicates. Compare with Jovian planets.

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