Transcript Oceanic Topography

OCEANIC TOPOGRAPHY
By Greg Schwab
May 7, 2007
Competency 39
• The teacher understands structure and
function of the hydrosphere
39.9
• The beginning teacher identifies the
characteristics of different ocean zones
(e.g., coastal, lighted, deep, estuaries,
bays).
TEKS: Geology, Meteorology,
Oceanography
• (11) The student knows characteristics of
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oceans. The student is expected to:
(11A) Identify physical characteristics of ocean
water including salinity, heat capacity, colligative
properties, and density.
(11C) Compare the topography of the ocean
floor to the topography of the continents.
Word Wall
Continental Shelf
Continental Slope
Continental Rise
Oceanic Basin
Oceanic Ridges
Oceanic Trenches
Seamount
Guyout
Atoll
Volcanic Island Arc
Bathymetric
Continental Shelf
A feature of the ocean floor; the flooded
margins of the continents that form a zone
of relatively shallow water adjacent to the
continents
Characteristics of the shelf
• Considered part of the continent not the ocean
• Slopes gently away from land for an average of
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75km (47 miles)
Average water depth is 130 m (425 ft)
Much wider on some parts of the continents
than other parts
Retains features of the adjacent land that is
above water
Continental Slope
A feature of the ocean floor; a steep slope
forming the transition between the
continental shelf and the deep ocean
basin.
Characteristics of the slope
• Transition between the continent and the
deep ocean basin
• Water depth ranges from 120 m (390 ft)
to 3,000 m (10,000 ft)
• Width of the slope is 20-40 km (12-25
miles)
• Steeper than the shelf
• Some slopes have submarine canyons
Submarine Canyons
• Long deep-sided trenches extending from
the top of the slope to the ocean basin
• Can be similar in size and depth to the
Grand Canyon
• Believe to been formed by turbidity
currents (a muddy current produced by
underwater landslides)
Continental Rise
The Transitional area of the continental
margin between the continental slope and
the abyssal plain.
Characteristics of rise
• Less steep than continental slope
• Created mainly by sediment deposits from
turbidity currents flowing down submarine
canyons.
Continental Margin
Composed of the continental shelf,
continental slope, and continental rise.
North American East Coast
North American Gulf Coast
North American East Coast
North American West Coast
North American West Coast
Ocean Basin
The deep bottom of the ocean floor, which
starts beyond the continental slope.
Characteristics of the Basin
• Deepest part of the ocean floor
• Under 4-6 km (2-4 miles) of seawater
• Features include: Abyssal plain, Oceanic
ridges, Oceanic trenches, and Seamounts
• Ocean basin and ridges cover more than
half the earth’s surface
• More surface area than all of the land
continents
Abyssal Plain
The practically level plain of the ocean
basin.
• Covers an area equal to the continental
land mass
Oceanic Ridges
Long, high, continuous, sub-oceanic
mountain chains; for example, the MidAtlantic Ridge in the center of the Atlantic
Ocean Basin
Characteristics of ridges
• Part of a chain of mountains that are
84,000 km long
• Mid-Atlantic Ridge is longest mountain
chain on earth
• Ridges are spreading centers or divergent
plate boundaries where new ocean floor is
created
Oceanic Trenches
Long, narrow, deep troughs with steep sides
that run parallel to the edge of continents
Characteristics of trenches
• Extend 8-11 km below sea level
• Long narrow basins
• Develop adjacent to subduction zones
• Zone of convergence
• Form parallel to continents
Seamounts
Steep submerged volcanic peaks on the
abyssal plain.
Characteristics of seamounts
• More than 10,000 scatter the ocean basin
• By definition rise more than 1 km (0.6
miles) above the ocean floor.
• Can extend above sea level (called an
island)
• Most Pacific Basin islands are seamounts.
Guyout
• A flat topped seamount which has
subsided beneath the water’s surface
because of wave action.
Atoll
Volcanic Island Arcs
• Curving Chains of volcanic islands that
occur over belts of deep-seated
earthquakes
• For example the Aleutian Islands are
volcanic island arcs, formed over the
Aleutian oceanic trench
Bathymetric
• Measurement of depths of the oceans;
also the data derived from such
measurement, especially as compiled in a
topographic map.
Exploring the Ocean Floor
• Challenging at best
• Single soundings
• Sonar (single beam)
• Multibeam sonar
• Sidescan Sonar
• Satellite surface water topography
Ocean Topography Quiz
• 1. Most seamount islands are found in the
___________ Ocean Basin.
• 2. T/F Volcanic Island arcs are associated with
subduction zones in zones of convergence?
• 3. In ocean basins, the youngest crust material
would be found closest to or farthest from the
oceanic ridge?
Ocean Topography Quiz
• 4. Submarine canyons are associated with
what part of the ocean’s topography?
• 5. The continental shelf is an extension of
the __________?
• 6. What is the longest mountain chain on
earth?
Ocean Topography Quiz
• 7. For the North American Continent, the
continental slope would be steeper on the east
or west coast?
• 8. The best surfing would be on the west or
east coast of North America?
• 9. The most accessible beaches in North
America would be on the west or east coast?