Earth's Physical Characteristics
Lithosphere
the rigid outer part of the earth, consisting of the crust and upper mantle. |
Mantle Convection
Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior of the Earth to the surface.
Mid-Ocean Ridge
A mid-ocean ridge is an underwater mountain system formed by plate tectonics. |
Pangaea
Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. |
Seafloor Spreading
the formation of new areas of oceanic crust, which occurs through the upwelling of magma at mid-ocean ridges and its subsequent outward movement on either side.
Subduction
the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate. |
Tectonic Plates |
the lithosphere of the earth is divided into a small number of plates which float on and travel independently over the mantle and much of the earth's seismic activity occurs at the boundaries of these plates. |
Tectonic Plate Boundary |
A boundary between two or more plates.
Transform plate boundary |
tectonic boundary. In the theory of plate tectonics, a boundary between two or more plates.
Continental Drift |
the gradual movement of the continents across the earth's surface through time. |
Convection
the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in the transfer of heat. |
Convection Currents |
A current in a fluid that results from convection. |
Convergent Plate Boundaries |
A tectonic boundary where two plates are moving toward each other. If the two plates are of equal density, they usually push up against each other, forming a mountain chain. |
Divergent Plate Boundaries |
A tectonic boundary where two plates are moving away from each other and new crust is forming from magma that rises to the Earth's surface between the two plates. |
Gondwana
A vast continental area believed to have existed in the southern hemisphere and to have resulted from the breakup of Pangaea in Mesozoic times. It comprised present-day Arabia, Africa, South America, Antarctica, Australia, and the peninsula of India. |
Laurasia
The supercontinent of the Northern Hemisphere that, according to the theory of plate tectonics, broke up into North America, Greenland, Europe, and Asia except for the Indian subcontinent. |