Ocean Floor Features

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Ocean Floor Features
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(No Transcript)
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http//ga.water.usgs.gov/edu/waterdistribution.htm
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Source Nace, U.S. Geological Survey, 1967
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East Coast of the U.S.
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How are the ocean floor features found?
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SONAR

• Sound
• Navigation
• Range
• The echo sounder calculates water depth by
  measuring time between emission of a sound signal
  directed toward the ocean floor and the return
  echo.

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Atlantic Ocean Floor Profile
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Ocean Profile
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Ocean Profile
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Topography of the Ocean Floor

• Continental Shelf

• Continental Slope

• Submarine Canyon

• Abyssal Plain

• Seamount

• Mid-Ocean Ridge

• Rift Zone

• Ocean Trench

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Continental Shelf Slope

• Continental shelf a relatively flat part of the
  continent covered by seawater. Lies between the
  coast and the continental slope.

• Continental slope steeply dipping surface
  between the continental shelf and the deep ocean
  basin.

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Continental Shelf Slope
San Francisco
Monterey Bay
The shelf break marks a distinct change in the
slope of the sea floor from the flat continental
shelf to the steep sea floor of the continental
slope.
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CONTINENTAL SHELF

• About 8 of the global seafloor area
• Source of fish, both commercial and sport, and in
  some areas, oil and natural gas.
• Varies in size off the coasts of the U.S.
• West coast narrow
• East coast - wide

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CONTINENTAL SLOPE

• Gradually rises from the abyssal plain but climbs
  as much as 45 degrees as it approaches land.
• Continental Rise - sediment deposits at the base
  of the slope
• Slopes are often gouged by deep valleys or
  submarine canyons

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Submarine Canyon
HUDSON CANYON
CONTINENTAL SHELF
CONTINENTAL SLOPE
HUDSON CANYON - First discovered in 1864
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Submarine Canyons
San Francisco
Canyon leading into Monterey Bay

• Submarine canyons are v-shaped canyons cut into
  the continental slope. Many canyons are
  associated with major rivers such as the Congo,
  Hudson, and others.
• most canyons were originally formed during the
  last Ice Age when the water level was lower
• some are the result of earthquakes.

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ABYSSAL PLAIN

• The true ocean floor
• Result of sediment drifting downward to fill
  depressions of the rocky ocean floor
• remains of marine life
• fine, clay-sized particles (ooze)

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Abyssal Plain
Continental shelf
Continental slope
Abyssal Plain
The abyssal plain is the flat, almost level area
of the deep ocean basin.
OOZE!!!
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Seamount
seamounts
Coast of central California
Monterey
Same area, different perspective
A volcanic mountain found on an ocean basin. It
is not a result of subduction or formed at the
mid-ocean ridge. Possibly an island that has
since eroded.
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SEAMOUNT GUYOT

• Isolated mountains rising from 3,000 to 10,000
  feet above the surrounding seabed.
• Volcanic origin
• Seamounts are found in all oceans, but are more
  numerous in the Pacific Ocean, with over 2,000
  identified.
• Guyots flat-top seamounts

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SEAMOUNT GUYOT
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Map of Seamounts
K. Stocks. 2003. Map of Sampled Seamounts.
SeamountsOnline an online information system for
seamount biology. World Wide Web electronic
publication. http//seamounts.sdsc.edu.
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Mid-Ocean Ridge
Mid-Atlantic Ridge
Underwater mountain chain that rises from the
ocean basins. Created by rising magma.
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Map view showing sea floor spreading at the
Mid-Atlantic ridge.
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MID-OCEAN RIDGE
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MID-OCEAN RIDGE

• Several mid-ocean ridges are longer than the
  longest mountain ranges on Earth.
• Can rise to above sea level to form islands
• Iceland and the Azores - Atlantic Ocean
• Galapagos Islands in the Pacific Ocean.
• Most of the ridges crest at a depth of about
  8,000 feet

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MID-OCEAN RIDGE

• Oceanic ridges have two peaks, separated by a
  rift valley. The valley ranges from 15 to 30
  miles in width and contains an active seismic
  area.

Americas
Africa / Europe
Example of the Mid-Atlantic Ridge
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Rift Zone
A system of cracks in Earths crust through which
molten material rises. Rift zones are found in
the middle of the mid-ocean ridges. Strange
animal life and unique geologic structures have
been found here.
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Rift Zone

• Divergent zones are where two plates are moving
  apart
• Convection currents are rising, bringing up heat
• Earthquakes and volcanic activity

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29 N
Volcanic ridge on zero-age crust, note small and
larger volcanic cones. See cratered volcano at
the top? The narrow, linear, bright features in
the rest of the image are fault scarps. Uniform
gray areas are sediment accumulating.
Rift Zone
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Black Smokers
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Black Smokers
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Black Smokers
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Trench
A deep trough on the ocean floor where oceanic
crust is forced below continental or other
oceanic crust.
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TRENCH

• Found at subduction zones (near continents and
  island chains)
• At least 26 trenches have been identified
• 22 are in the Pacific Ocean
• 1in the Atlantic Ocean (Puerto Rico Trench)
• 1in the Indian Ocean (Java Trench)

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TRENCH
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TRENCH

• Depths of major trenches exceed 18,000 feet, and
  vary from 10 to 22 miles in width.
• The deepest is the Challenger Deep, 35,810 feet
  deep, in the Marianas Trench Mount Everest -
  29,028 feet
• Trenches are not the same
• Peru-Chile Trench off the west coast of South
  America is nearly 1,100 miles long.
• The Japan Trench is 150 miles long and is the
  shortest.
• The Tonga Trench, located between New Zealand and
  Samoa, is the narrowest and straightest.
• The Kurile Trench between Japan and Kamchatka is
  the widest.

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MarIana Trench