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Ocean Landforms
Revealing the Ocean Floor
• If you could travel to the bottom
of the ocean, you would see the
world’s largest mountain chain
and canyons much deeper than
the Grand Canyon.
• How can the ocean floor be
mapped?
Revealing the Ocean Floor
 Sonar (stands for Sound
Navigation and Ranging)
 Invented in the 1920s
 Primary instrument for
measuring depth
 Reflects sound from ocean
floor
Revealing the Ocean Floor
 Use of satellites for mapping
 Employs satellites equipped with radar
altimeters
 Scientists are able to measure the
direction and speed of ocean currents.
 Measure the different heights of the
ocean surface to make maps of ocean
floor.
 Can cover more territory using
satellites rather than ship sonar.
Continental Shelf
• Begins at the shoreline
• Continues until it begins to slope
more steeply downward
• Depth can reach 200 meters
• This is what you walk on at the
beach.
Continental Slope
•Begins at the edge of shelf
and continues to flattest part
of ocean floor
•Depth ranges from 200
meters to 4000 meters
•Continent ends at bottom of
continental slope
Abyssal Plain
• Broad, flat portion of the deep-
ocean floor.
• Covered with mud and remains of
marine organisms.
• Average depth is 4,000 meters
Mid-Ocean Ridges
• Mountain chains formed where
tectonic plates pull apart.
• Pulling motion creates cracks in
the crust called rift zones.
• Rift Valley forms between
mountains in the mid-ocean ridge.
Seamounts
• Individual mountains of volcanic
material.
• If a seamount builds up above
sea level, it becomes an island.
• A guyot is a flat-topped
seamount.
Actual footage of an erupting
underwater volcano.
Ocean Trench
• Seemingly bottomless cracks in
the ocean basin.
• Formed where one oceanic plate
is forced underneath another
plate.
• Most famous: Marianas Trench