Earth Science 12^th Edition

Chapter 13 Vocabulary

By Megan Andrews (GLY 1001 Student North Campus Fall 2006)

Abyssal plain- very level area of the deep ocean floor, usually lying at the foot of the continental rise.

Active continental margin- usually narrow and consisting of highly deformed sediments. They occur where oceanic lithosphere is being sub ducted beneath the margin of a continent.

Bathymetry- measurement of ocean depths and the shape or topography of the ocean floor.

Biogenous sediment- seafloor sediments consisting of material of marine organic origin.

Continental margin- portion of seafloor continents. Includes shelf, slope and rise.

Continental shelf- gently loping surface at submerged portion of the continental margin, extending from the shoreline to the continental slope.

Continental slope- steep gradient that leads to the deep ocean floor and marks seaward edge of the continental shelf.

Continental rise- gently sloping surface at the base of the continental slope.

Continental volcanic arc- mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent.

Deep ocean trench- the portion of seafloor that lies between the continental margin and oceanic ridge system.

Deep sea fan- a cone shaped deposit at the base of the continental slope; the sediment is transported to the fan by turbidity currents that follow submarine canyons.

Echo sounder- an instrument used to determine the depth of water by measuring the time between emission of a sound signal and return of its echo from the bottom.

Gas hydrate- 378 unusually compact chemical structures made of water and natural gas.

Graded bedding- a sediment layer that is characterized by a decrease in sediment size from bottom to top.

Guyot- a submerged flat topped seamount.

Hydrogenous sediment- seafloor sediments consisting of minerals that crystallizes from seawater example of manogese nodules.

Mid ocean ridge- along well developed divergent plate boundaries the seafloor is elevated forming a broad linear swell.

Ocean basin floor or deep-ocean basin- area of the deepest ocean between the continental margin and the mid ocean ridge.

Oceanic plateau- an extensive region on the ocean floor composed of thick accumulations of pillow basalts and other mafic rocks.

Oceanic ridge- continuous elevated zone on the floor of all the major ocean basins and verifying inn width from 500-50000 km’s.

Oceanography- scientific study of the oceans and oceanic phenomena.

Passive continental margin- margins that consist of a continental shelf continental slope and continental rise. Not associated with plate boundaries and experience little volcanic and earthquakes.

Rift valley- along the axis of some segment of the oceanic ridge system is deep down faulted structures.

Seamount- an isolated volcanic peak that rises at least 1000 meters above the deep ocean floor.

Seismic reflection profile- strong low profile frequency sounds are produced by expulsions depth charges or air guns penetrate off seafloor reflects off contacts between rock layers and fault zones.

Sonar- acronym for sound navigation and ranging.

Submarine canyon- deep steep sided valleys out into continental slope and may extend across the entire continental rise to the ocean basin floor.

Table mount- submerged flat topped seamount.

Terrigenous sediment- seafloor sediment derived from terrestrial weathering and erosion.

Turbidite- turbidity current deposit chacterized graded bedding.

Turbidity current- down slope movement of dense sediment –laden water created sand ad mud on the continental slope and shelf are dislodged and thrown into suspension.

Volcanic island arc- chain of volcanic islands generally located a few 100 km.’s from a trench where active subdution of one oceanic slab beneath another is occurring.