Chapter 13

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