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seafloor spreading

(Encyclopedia)CE5 Schematic model of the oceanic crust, showing seafloor spreading seafloor spreading, theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwate...

Tharp, Marie

(Encyclopedia)Tharp, Marie, 1920–2006, American oceanographer and cartographer, grad. Univ. of Michigan (M.A. 1944). A geologist with experience in mapping, she came to Columbia Univ. as a geology research assist...

Hess, Harry Hammond

(Encyclopedia)Hess, Harry Hammond, 1906–69, American geologist and oceanographer, b. New York City, B.S., Yale, 1931, Ph.D., Princeton, 1932. He taught at Rutgers (1932–33) and was a research associate at the G...

rift valley

(Encyclopedia)rift valley, elongated depression, trough, or graben in the earth's crust, bounded on both sides by normal faults and occurring on the continents or under the oceans. The central flat block forming th...

subduction zone

(Encyclopedia)subduction zone, large-scaled narrow region in the earth's crust where, according to plate tectonics, masses of the spreading oceanic lithosphere bend downward into the earth along the leading edges o...

subsidence

(Encyclopedia)subsidence, lowering of a portion of the earth's crust. The subsidence of land areas over time has resulted in submergence by shallow seas (see oceans). Land subsidence can occur naturally or through ...

Ewing, William Maurice

(Encyclopedia)Ewing, William Maurice, 1906–74, American oceanographer and geologist, b. Lackney, Tex., grad. Rice Institute, now Rice Univ. (B.S., 1926; M.A., 1927; Ph.D., 1931). He taught physics and geology at ...

plate tectonics

(Encyclopedia)CE5 Plate tectonics: Map of the world showing major plates and plate boundaries CE5 Plate tectonics: Schematic model of the oceanic crust, showing the three types of plate boundaries plate tect...

hydrothermal vent

(Encyclopedia)hydrothermal vent, crack along a rift or ridge in the deep ocean floor that spews out water heated to high temperatures by the magma under the earth's crust. Some vents are in areas of seafloor spread...

Mesozoic era

(Encyclopedia)Mesozoic era mĕzˌəzōˈĭk [key] [Gr.,=middle life], major division of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 65 to 225 million years ago. Great crustal disturb...