Transcript Features of the Ocean Basins

The Ocean Basins
Physical Oceanography
Features of the Ocean Basins
• Continental margin: portion of
ocean made up of continental crust
Features of the Ocean Basins
• continental shelf:
flat part of continental
margin covered by shallow ocean water
Formed by changes in sea level
Avg depth = 60 m
Shelf
• Relatively shallow
• 0 – 200 m
• Relatively flat with
a gradient of 2 m
drop per kilometre
Features of the Ocean Basins
• continental slope:
boundary between
continental crust and oceanic crust - The average
angle displayed by the slope is about 5 degrees.
Features of the Ocean Basins
• submarine canyons: deep, v-shaped
valley that cuts through shelf & slope
Features of the Ocean Basins
• continental rise: wedge of sediments
that separates slope from ocean floor
Features of the Ocean Basins
• abyssal plain (floor): very flat areas at
depths of 3-5 km
Features of the Ocean Basins
• mid-ocean ridge: mountain range on
ocean floor due to seafloor spreading
Features of the Ocean Basins
• trench: deep narrow valleys along the edges of subduction
zones in the ocean floor; 90% of trenches are found around the
Pacific rim.
Marianas Trench in Pacific ocean is the deepest point on
earth - 10,668 meters
Bathymetric Charts – show the contours and depths of the
seafloor topography
General Slope Features
• Sharp break from the shelf
• Angle is gentle, averaging less than 5
degrees
• Continues to a depth of 3600 m
• Often carved by deep canyons - Hudson
Canyon is famous in N.A.
Submarine Canyons
• V-shaped
• Hudson Canyon steeper than the Grand
Canyon
• Form deep sea fans from sediments
• Originated from rivers during ice ages
The
Gully!
Submarine canyon off Nova Scotia
•
• Marine protected area because of the rare corals found there
• The natural gas pipeline goes right by it…problems?
The Gully
Turbidity currents
• Turbidity currents are caused by the
slumping of sediments from the continental
slope.
• can travel at over 55 km/h
• can spread 700 km+
• Can damage underwater pipelines,
transatlantic cables
Rise
• Slope about ½ degree toward the
abyssal plain
• Sediment deposition from continent
• Range from 100 to 1000 km in width
• Only occur along passive margins,
often off the mouth of large rivers
Another look 
Features of the Ocean Basins
• seamount: underwater volcanic
mountain (some more than 1000 m high)
•
Features of the Ocean Basins
Atolls
A ring shaped island of coral reefs and coral debris.
These often form over sinking inactive volcanoes.
Features of the Ocean Basins
• coral reef: limestone structures
containing shells of animals that
surround volcanic islands
Features of the Ocean Basins
• guyot: a flat-topped submerged
seamount due to erosion
Features of the Ocean Basins
• rift valley: deep crevice in between
mountain ranges
Which coast has the wider shelf?