geo-, ge- +

In cartography, or maps, the plane through the center of the Earth: The geocentric horizon is parallel to the topocentric (a point on the surface of the Earth) horizon:

1. In astronomy, the angular distance in degrees which a celestial object lies north or south of the Earth's equator: The students in Mr. Green's class were asked to locate the geocentric latitude of the planet he assigned them.
2. In geodesy, the angle formed with the major axis of the ellipse (stretched circle with slightly longer, flatter sides) by the radius vector (magnitude and a direction) from the center of the ellipse to the given point: The geocentric latitude is the position on the Earth's surface, the angle between the place of the equator and the center of the Earth.

The angular distance in degrees that a celestial object lies east or west of Greenwich Meridian, or the meridian passing through Greenwich (Greater London borough on the Thames in England: The geocentric longitude was internationally adopted as the Earth's zero of longitude in 1884.

The change in an astronomical object's apparent position: A geocentric parallax is caused by the change in the observer's earthly position because of the motion of the Earth during the day.

In history, the ancient belief that the sun and other bodies of the solar system revolve around the Earth: The geocentric theory was stated in detail by Ptolemy about 140 A.D. and later replaced by the heliocentric theory of Copernicus.

The point at which a line from the center of the Earth through a point on its surface meets the celestial sphere: The geocentric zenith Mr. Tall showed his class was viewed on a model of the universe.

The belief that the Earth is the center of the universe: The opinion that the sun revolved around the Earth and that the Earth was stationary was all the rage in Galileo's day.

In mineralogy, a white, flaky, wax-like hydrocarbon or any of numerous organic compounds which contain only oxygen, carbon and hydrogen: So far geocerite is only found in brown coal.

A reference to the study of the chemical composition of the various phases of the Earth and the physical and chemical processes which have produced the observed distribution of the elements and nuclides in these phases: Geochemical investigations are concerned with the chemistry of the Earth, including the rocks, sediments, and soil that constitute the solid Earth and the fluids which compose the oceans, inland waters, and the atmosphere.

In geochemistry, an unusually high concentration of one or more chemical elements in a sample of rock, soil, vegetation, or water: A geochemical anomaly is a high concentration of hydrocarbons in soil which often indicates a nearby mineral deposit.

The study of the global distribution and the migration of a particular element, mineral, or compound, including the amount liberated by weathering and transported to the Earth sediments and oceans: One example of geochemical balance can be exemplified by the distribution of quartz in igneous rocks, its liberation by weathering, and its redistribution into sediments and in solutions, into lakes, rivers, and oceans.

Sediments refer to solid fragments of inorganic or organic material that come from the weathering (disintegration and decomposition) of rock and are carried and deposited by wind, water, or ice.

In Earth science, the successive stages in the circulation and migration of chemical elements among the lithosphere, hydrosphere, and atmosphere during geological changes: The geochemical cycle is the route or the course that chemical elements travel in the surface and crust of the planet Earth.

Over geological time any change in the chemical composition of some section of the Earth: Geochemical evolution is an important factor in the oceans.

Geochemical evolution is any alteration or change in the chemical composition of a rock in which the amount of a particular component exceeds the amount present in the parent rock.

A geologist or chemist who is an expert in geochemistry: Dr. Evens was a geochemist who knew a lot about the chemical composition of the Earth and various planets.

The scientific study of the chemistry of the Earth, including the rocks, sediments, and soil that constitute the solid Earth and the fluids that compose the ocean, inland waters, and the atmosphere: Geochemistry refers to chemical reactions involving Earth materials, such as soil, rocks, and water.

Geochemistry is the chemistry of the composition and alterations of the solid matter of the Earth or of a celestial body.

The study of the chemistry of the Earth includes the study of the rocks and sediments that constitute the solid Earth, as well as the fluids of the oceans, inland waters, and the atmosphere.

Geochemistry is based on a foundation of other sciences, including chemistry, geology, physics, and biology. This field of research concentrates on the movement, or flux, of chemical elements through the solids and fluids of the Earth.