Plate tectonics
a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past adjacent plates.
a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past adjacent plates.
Continental Drift
The theory that the earth's continents move gradually over the surface of the planet on a substratum of magma.
The theory that the earth's continents move gradually over the surface of the planet on a substratum of magma.
Pangaea
the hypothetical landmass that existed when all continents were joined, from about 300 to 200 million years ago.
the hypothetical landmass that existed when all continents were joined, from about 300 to 200 million years ago.
Asthenosphere
the region below the lithosphere, variously estimated as being from fifty to several hundred miles (eighty-five to several hundred kilometers) thick, in which the rock is less rigid than that above and below but rigid enough to transmit transverse seismic waves.
the region below the lithosphere, variously estimated as being from fifty to several hundred miles (eighty-five to several hundred kilometers) thick, in which the rock is less rigid than that above and below but rigid enough to transmit transverse seismic waves.
Lithosphere
the rigid outer part of the earth, consisting of the crust and upper mantle.
the rigid outer part of the earth, consisting of the crust and upper mantle.
Mid-Oceanic ridge
any of several seismically active submarine mountain ranges that extend through the Atlantic, Indian, and South Pacific oceans: each is hypothesized to be the locus of seafloor spreading.
any of several seismically active submarine mountain ranges that extend through the Atlantic, Indian, and South Pacific oceans: each is hypothesized to be the locus of seafloor spreading.
Rift valleys
a long narrow valley resulting from the subsidence of land between two parallel faults, often associated with volcanism. The East African Rift Valley is an example
a long narrow valley resulting from the subsidence of land between two parallel faults, often associated with volcanism. The East African Rift Valley is an example
Subduction
the process of one tectonic plate sliding under another, resulting in tensions and faulting in the earth's crust, with earthquakes and volcanic eruptions
the process of one tectonic plate sliding under another, resulting in tensions and faulting in the earth's crust, with earthquakes and volcanic eruptions