Download (granite) and the deep

THE WORLD OCEAN
Covers 71 % of the planet (59.4 % is seafloor)
Divided into major basins –
Atlantic (N & S)
Pacific
Arctic
Indian
Southern
Pacific – largest & deepest
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BATHYMETRY OF THE OCEAN FLOOR
Structures on the ocean floor are mapped by SONAR sound navigation and ranging (echo sounding)
(speed of sound in H20)
depth = time x 1460 meters/sec
2 (round trip)
sea floor
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Continental Margin: the submerged outer edge of a continent
marks the transition between continent and ocean, composed
of shelf, slope & rise
a. continental shelf - underwater extension of the continent, most
biologically productive area because of light availability
b. continental slope – sloping transition between the continent
(granite) and the deep-ocean floor (basalt)
- sediments tumbling down the slope can form turbidity
currents which cut submarine canyons (deep, V-shaped valley
running perpendicular to the shoreline)
c. continental rise – wedge of sediments covering the
joint between ocean crust and continental crust
NOAA
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Ocean Basin:
a. abyssal plain - flat, featureless region similar to a desert;
common in Atlantic and Indian Oceans, rare in the Pacific
b. abyssal hill - occur where sediment is not thick enough to cover
the underlying rock completely. Usually extinct volcanoes or small
formations of rock once extruded in molten form.
c. seamount - peaks of volcanic mountains (sea mountains)
d. guyot - submerged, inactive volcano
truncated by erosion; like “plateaus”
e. island - seamounts extending out of the water.
They differ from continents because they have no
margins.
Volcanic eruptions create and destroy the terrain.
Hot spots under moving plates cause island arcs
such as the Hawaiian Island chain. Parts of the
chain are submerged. More about this later . . . 5
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Hawaii’s volcano, Mauna Kea, is the highest mountain on Earth.
It’s 31,000 ft. from the Pacific
floor - although only 13,823 ft.
of it are above water.
f. trenches – arc-shaped depression in the deep-ocean floor with
very steep sides and flat sediment-filled bottoms, associated with
subduction zones where ocean crust is being recycled into the
mantle
Trenches form a boundary around the Pacific; called the Ring of
Fire because of the volcanic and seismic activity.
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Mt. Everest, at 29,000 ft., could fit into
the Mariana trench and still be 7,000
ft. below sea level.
g. MOR - 40,000 mile long mountain range
where new oceanic floor is being formed.
Divergent plate boundaries are found in all
parts of the ocean - not just in the middle of
the Atlantic.
NOAA
Iceland is a large section of the
MOR extending above the water.
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h. rift “valley” – down-dropped section of a MOR occurring at
divergent plate boundaries, outpouring of magma creates new
ocean floor
NASA
Oceanic bathymetry is very similar to continental topography
except that continent features are smaller due to erosion
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