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Warm Up 2/6/09
What technology do scientists use to measure ocean depth?
a. sonar
c. rope
b. submersible
d. laser
2. Differences in ocean-surface height can be measured by
a. satellites
c. submersibles
b. sonar
d. none of the above
3. Approximately how much of Earth’s surface is covered by
a. 60 percent
c. 30 percent
b. 70 percent
d. 50 percent
Answers: 1) a. 2) a. 3) c.
Ocean Floor Features
Chapter 14, Section 2
Profile of North Atlantic Ocean
Continental Margins
Continental Margin – the zone of transition
between a continent and the adjacent ocean
basin floor
In the Atlantic Ocean, thick layers of
undisturbed sediment cover the continental
margin. This region has very little volcanic or
earthquake activity
In the Pacific Ocean, oceanic crust is plunging
beneath continental crust. This force results in a
narrow continental margin that experiences both
volcanic activity and earthquakes
Passive Continental Margin
Continental Shelves, Slopes, and Rises
Continental Shelf – the gently sloping submerged
surface extending from the shoreline
Continental shelves contain important mineral
deposits, large reservoirs of oil and natural gas, and
huge sand and gravel deposits
Continental Slope – the seaward edge of the
continental shelf
The continental slope is a relatively narrow feature
along the continental shelf
Continental Shelves, Slopes, and
Rises Continued
Submarine Canyon – deep, steep-sided valleys
cut into the continental slope
Turbidity Currents – occasional movements of
dense, sediment-rich water down the continental
Turbidity currents are known to be an important
factor in sediment transfer in the ocean
Continental Rise – a gradual incline which
merges with the steep continental margin,
occurs in regions where trenches do not exist
Submarine Canyons
Concept Check
Compare and contrast the continental slope and
continental rise.
Continental slope marks the steep boundary
between continental crust and oceanic crust.
The continental rise occurs at the end of the
continental slope and has a more gradual incline.
Ocean Basin Floor
Ocean Basin Floor – area between the continental
margin and the mid-ocean ridge
Deep-ocean trenches are long, narrow creases in the
ocean floor that form the deepest parts of the ocean
Trenches form at sites of plate convergence where
one moving plate descends beneath another and
plunges back into the mantle
Abyssal Plains – deep, extremely flat features and are
the most level places on Earth
The sediments that make up abyssal plains are carried
there by turbidity currents or deposited as a result of
suspended sediments settling
Ocean Basin Floor Continued
Seamounts – the submerged volcanic peaks
which dot the ocean floor
Once underwater volcanoes reach the surface,
they form islands
After millions of years, the tops are eroded away
and the once active islands sink back into the
ocean, forming guyots
Abyssal Plain
Concept Check
What are abyssal plains?
Deep, extremely flat regions of the ocean floor.
Mid-Ocean Ridges
Mid-Ocean Ridge – found near the center of most
ocean basins; an interconnected system of underwater
mountains that have developed on newly formed ocean
Seafloor Spreading – occurs at divergent plate
boundaries where two lithospheric plates are moving
New ocean floor is formed at mid-ocean ridges as
magma rises between the diverging plates and cools
Hydrothermal vents form along mid-ocean ridges and
are zones where mineral-rich water escapes through
cracks in oceanic crust into the surrounding cooler
Profile of North Atlantic Ocean
Assignment (Due 2/13)
Read Chapter 14 (pg. 394-413)
Do Chapter 14 Assessment #1-33 (pg. 417-418)
Cool Down
What is formed at mid-ocean ridges?
New ocean floor
Compare and contrast seamounts and guyots.
A seamount is an underwater volcano that has
not reached the surface yet. A guyot is a
volcanic island that has been eroded and sunk
back under the water’s surface.
What is one thing new that you learned today?
Explain what it is.
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