1. Features of the Ocean Floor
Ms. Bridgeland
6th Grade

2. Features of the Ocean Floor
What do you think the Ocean Floor looks like?
Raise your hand if you think that it is flat?
Raise your hand if you think that it is uneven?

3. It is a surprise to many that the ocean floor looks like this….

4. Features of the Ocean Floor
continental shelf –shallow area of ocean floor
continental slope-steep edge of the continental shelf
abyssal plain-smooth, flat region of the ocean floor
mid-ocean ridge-range of mountains that passes through all of Earth’s oceans

5. In Shallow Water: Continental shelf
Continental slope: end of shelf and beginning of slope marks where continental rock ends & oceanic rock begins
Think of Nemo… “The drop-off!”

6. In Open Ocean:
Abyssal Plain: thick layers of sediment lie here, formed by remains of dead organisms
Mid-Ocean Ridge: mountain range along both sides of a central valley –this chain runs through all the oceans in the world
Remember this is where sea-floor spreading occurs magma erupts here and produces new ocean floor

7. Continental Shelf

8. Continental Shelf
*Still considered to be part of the continents (continental rock) *Average width is 40 miles (65 km), but width varies ex. in parts of California = less than 1 km ex. along northern coast of Siberia = 1,290 km (800 miles) *only about 7% of the entire ocean floor

9. Continental Slope Drops down at a sharp angle
Marks the true edge of a continent, transition from continental crust to oceanic crust
Extends from edge of continental shelf to the abyssal plain (between ,200 meters ( ,500 feet)
Most Pacific slopes are steeper than Atlantic slopes
About 8.5% of ocean floor is made up of continental slopes

10. Abyssal Plain The smooth, nearly flat region of the ocean floor
Has thick layers of sediment, formed by the remains of dead organisms from the surface
Remember: FLAT REGION

11. Abyssal Plain

12. Mid-ocean ridge
A continuous range of mountains that winds around the Earth
Formed by plate tectonics
Passes through all of Earth’s oceans
Nearly 80,000 kilometers long
Longest mountain range on earth
Consists of many peaks along both sides of a central valley
Some mountains along the ridge reach above sea level, forming island groups (ex. Azores islands in Portugal)

13. Azores Islands –part of the mountains that make up the mid-ocean ridge

14. Mid-ocean ridge is several times longer than the Andes

15. Mid-Ocean Ridge

16. Seafloor Spreading happens at the Mid-Ocean Ridge
Plates “diverge” or move apart
Along the ridge, magma (lava) squeezes up through the cracks, and as it hardens, it adds a new strip of rock to the ocean floor

17. Trench: A deep, steep-sided canyon or “hole” in the ocean floor

18. Mariana Trench
The deepest trench in the world and the deepest part of the world’s ocean
Mariana Trench is more than five times as long as the Grand Canyon

19. Mariana Trench is deeper than Mount Everest is tall

21. Trenches are formed by Converging Plates
When plates are pushed together, one plate sinks under the other

22. Converging Plates

23. Features of the ocean floor: Volcanic Islands

24. Volcanic Islands:
Appear on the abyssal plain
When they erupt, they create mountains whose peaks break the surface of the ocean
When lava cools, islands are formed

25. Volcanic Islands: Galapagos Islands (west of continental Ecuador)

26. Volcanic activity causes Galapagos Islands to have a unique climate with unique animals that live nowhere else in the world

27. Volcanic Islands

28. Volcanic Islands

29. Seamounts
Mountains whose peaks do not break the surface of the ocean water, and thus are NOT islands
Still formed by volcanic activity

30. Seamounts Provide habitats for organisms
Nutrients are carried upwards toward the sunlit surface, providing food for creatures like corals, fish, & crustaceans

31. Seamounts