Features of the Ocean Floor Ms. Bridgeland 6th Grade

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?

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

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

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!”

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

Continental Shelf

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

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 100 -3,200 meters (330 -10,500 feet) Most Pacific slopes are steeper than Atlantic slopes About 8.5% of ocean floor is made up of continental slopes

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

Abyssal Plain

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)

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

Mid-ocean ridge is several times longer than the Andes

Mid-Ocean Ridge

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

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

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

Mariana Trench is deeper than Mount Everest is tall

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

Converging Plates

Features of the ocean floor: Volcanic Islands

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

Volcanic Islands: Galapagos Islands (west of continental Ecuador)

Volcanic activity causes Galapagos Islands to have a unique climate with unique animals that live nowhere else in the world http://video.nationalgeographic.com/video/galapagos-unique-animals-lex

Volcanic Islands

Volcanic Islands

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

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

Seamounts