The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid. The term elevation is mainly used when referring to points on the Earth’s surface, while altitude or geopotential height is used for points above the surface. Elevation is not to be confused with the distance from the center of the Earth.

Mantle (geology)

A mantle is a layer within a planetary body that is bordered below by a core and above by a crust. Mantles are composed of rock or ice and are the biggest and most substantial layer of a planetary body. Mantles are found on planets that have experienced density differentiation. Mantles are found on all terrestrial planets (including Earth), a few of asteroids, and certain planetary moons.


A hypothesis (plural hypotheses) is an explanation proposed for a phenomena. The scientific method demands that a hypothesis be testable in order for it to be considered a scientific hypothesis. Scientists often develop scientific hypotheses on earlier data that cannot be explained satisfactorily by the established scientific theories. Despite the fact that the terms “hypothesis” and “theory” are sometimes used interchangeably, a scientific hypothesis is not the same as a scientific theory. A working hypothesis is a hypothesis that has been tentatively accepted and is being offered for further investigation, in a process that begins with an informed guess or notion.