Download Ocean Floor Features

Warm Up
1. 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 land?
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 slope
• 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 crust
• Seafloor Spreading – occurs at divergent plate
boundaries where two lithospheric plates are
moving apart
• 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 water
Profile of North Atlantic Ocean
Assignment
• Read Chapter 14, Section 2 (pg. 401-405)
• Do Chapter 14 Assessment #1-33 (pg. 417-418)
• For Section 2: Do #’s 4-6, 15-18, 26, 27, 30, 33
• For the Multiple Choice Questions (#1-10) write the
questions and answer.
• For the rest of the questions write in complete
sentences.