Download The Ocean Basin

The Ocean Basin
Ocean Basin Features
Continental Margins
Composed of the
 Continental shelf
 Continental slope
 Continental rise
Continental Shelf
A shallow submerged extension of the
continent.
 Exposed during times of low sea-level.
 Composed of continental crust.
 Gentle slope – 1.7 m/km (9 ft/mile)
 Ends at shelf break – the abrupt
increase in slope at the junction
between the continental shelf and
continental slope. Usually 140m deep.

Continental Slope
The transition between the gently
descending continental shelf and the
deep-ocean floor.
 Average angle 4 degrees. (The same as
a movie theater.)
 Extends from shelf break to the
continental rise or a trench.

Submarine Canyons
Cut into continental shelf and slope and
terminate on the sea-floor in a fan
shaped wedge of sediment.
 Mainly formed by turbidity currents –
underwater landslides. Sediment mixes
with water and the more dense mixture
moves downslope eroding the
continental slope with it.

Submarine Canyon
Turbidity Current

Sediments
produced
are called
turbidites.
Submarine Canyons – Con’t.
Some are drowned
valleys or are
extensions of
continental rivers.
 Hudson River Canyon.

3 km deep
 300 km out to sea.

Continental Rise
Wedge of sediment at the base of the
continental slope.
 Width varies from 100 km to 1000 km.

Active Continental Margins
Associated with active tectonic
processes. – Subduction, earthquakes,
volcanoes, faulting.
 Narrow continental shelf
 No continental rise.
 Continental slope usually terminates in
a deep-sea trench.

Active Continental Margins
Passive Continental Margins
No active tectonic process.
 Typically broad continental shelf.
 Continental slope terminates at the
continental rise.
 No trench.

Passive Continental Margin
Deep-Ocean Basins
Abyssal Plains
Flattened places on the ocean floor.
 Basaltic crust covered by sediments up
to 3 miles thick.

Abyssal Hills
1-10 km across.
 Approximately 100 m in height.

Sea Mounts

Undersea
Mountains
Guyots
Flat topped
seamount.
 Top eroded off
by wave
action, then
the mountain
sank below
sea level.

Trenches
Form at
subduction
zones.
 Deepest
places in
the ocean.

Mid Ocean Ridges
Divergent boundaries which usually
occur in the middle of oceans.
 Constantly forming new oceanic crust.
 Mid Ocean ridge system is 40,000 miles
long.

Mid Ocean Ridges
More M.O.R