1. Warm Up 2/6/09
What technology do scientists use to measure ocean depth?
a. sonar c. rope
b. submersible d. laser
Differences in ocean-surface height can be measured by ____.
a. satellites c. submersibles
b. sonar d. none of the above
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.

2. Ocean Floor Features
Chapter 14, Section 2

3. Profile of North Atlantic Ocean

4. 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

5. Passive Continental Margin

6. 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

7. 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

8. Submarine Canyons

9. 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.

10. 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

11. 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

12. Abyssal Plain

13. Concept Check What are abyssal plains?
Deep, extremely flat regions of the ocean floor.

14. 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

15. Profile of North Atlantic Ocean

16. Assignment (Due 2/13) Read Chapter 14 (pg. 394-413)
Do Chapter 14 Assessment #1-33 (pg )

17. 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.