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Geology Final


Measurement of ocean depths and the charting of the shape or topography of the ocean floor

Echo Sounder

Invented in the 1920's
Primary instrument for measuring depth
Reflects sound from ocean floor

Four main ocean basins

Pacific Ocean- the largest and has the greatest depth
Atlantic Ocean- about 1/2 the size of the pacific and not quite as deep
Indian Ocean- slightly smaller than the atlantic, largely a southern Hemisphere body
Arctic Ocean- about 7% the size of the Pacific

71% of Earth's surface

is represented by oceans and marginal seas

29% of the Earth's surface

Continents and islands compromise the rest

Northern Hemisphere

the land Hemisphere

Southern Hemisphere

the water Hemisphere

Multibeam Sonar

Employs and array of sound sources and listening devices
Obtains a profile of a narrow ship of sea floor

3 Major topographic units of the Ocean Floor

Continental margins
Ocean Basin Floor
Mid-Ocean ridge

Continental Shelf

Flooded extension of the contents
Varies greatly in width
Gently sloping
contains oil and important mineral deposits

Submarine Canyons

deep, steep sided valleys cut into the continental slope
Some are seaward extensions of river valleys
Most appear to have been eroded by forbidding currents

Passive Continental Margins

Features composing a passive continental margin
Found along most coastal areas that surround the Atlantic Ocean
Not associated with plate boundaries
Continental Slope
Relatively Sleep Structure
Boundary between

Continental Shelf

Some areas are mantled by extensive glacial deposits
Most consist of thick accumulations of shallow water sediments

Turbidity Currents

Downslope movements of dense, sediment laden water
Deposits are called turbidites

Continental Rise

Found in regions whee trenches are absent
Continental slope merges into a more gradual incline
Thick accumulation of sediment
At the base of the continental slope turbidity currents that follow submarine canyons deposit sediment that forms deep sea fans

Abyssal Plains

Likely the most level places on Earth
Sites of thick accumulations of sediment
Found in all oceans

Seamounts and guyots

Isolated volcanic peaks
Many form near oceanic ridges

Mid Ocean Ridge

Consist of layer upon layer
Mid-Atlantic Ridge has been studied more thoroughly than any other ridge system

Terrigenous Sediment

Material weathered from continental rocks
Virtually every part of the ocean receives some
Fine particles remain suspended for a long time
Oxidation often produces red and brown colored sediments

Biogeneous Sediment

Shells and Skeletons of marine animals and plants
Most common are calcareous oozes produced from microscopic organisms that inhabit warm surface waters
Silliceous oozes composed of skeletons of diatoms and radioiariams

Energy Resources

Oil and Gas
Gas Hydrate

Other Resources

Sand and gravel
Evaporate Salts
Manganese Nodules


The most common sediment on the deep ocean floor

Hydrogenous Sediment

Minerals that crystalize directly from seawater
Mangenese Nodules
Calcium Carbonate
Metal Sulfides

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