Download The Ocean Floor

The Ocean Floor
The Ocean Floor
Imagine flying around the world. Below you see a land filled with
mountains, plains and deep canyons. Now, picture this same area
somewhere under the ocean.
Under water there are also numerous hills, slopes and very deep
canyons as you can see from the ocean floor map on this slide.
The ocean looks very different without the water. Notice how easy it is
to see the mid-ocean ridge and all the other features of the ocean
bottom. We know about all this because of sonar.
What is sonar?
The Ocean Floor
• The sea bottom is divided into three areas:
* The continental shelf
* The continental slope
* The deep ocean floor
The Ocean Floor
The Continental Shelf
 Surrounds all continents
 Relatively shallow when compared to the other regions of the ocean
 Extends to the continental slope
 This region contains the highest amount of plant and animal life.
The Ocean Floor
The Continental Slope
 A steep drop off that leads toward the deep bottom of the ocean.
 Canyons cut through many areas of the continental slope.
How did the canyons get there?
The Ocean Floor
The Ocean Floor
 Much of the deep ocean floor is covered in basins
 Many mountain ranges spread across the ocean floor
 There are deep ocean trenches that are found in areas of volcanic
activity
The Ocean Floor
What causes the mountain ranges, and deep sea trenches on the
ocean floor?
Tell me in your own words:
•What creates the mid-ocean ridge?
•How do deep ocean trenches form?
The Ocean Floor
Plate Tectonics!!!
This is the movement of Earth's crustal plates (continental drift)
which causes mountains to push higher and oceans to grow wider.
Seafloor spreading causes oceans to grow wider and subduction
causes the deep ocean trenches to develop on the ocean floor.
Mid-Ocean Ridge
The Ocean Floor
In the following diagram there is evidence
of seafloor spreading by showing the ages
of the ocean floor.
The red colors are the youngest parts of the seafloor, where fresh new
crust is formed as lava seeps up from the deep interior of the Earth
at spreading ridges.
The green colors are the spreading ridges, older crust, that moves
away from the ridge as new crust is formed.
The blue colors are the oldest regions of the seafloor. They are either
next to continents, or are near areas on Earth where subduction is
taking place.
Deep Ocean Trench
The Ocean Floor
The deepest ocean trench is the
Marianas Trench in the South
Pacific Ocean, it is more than
35,000 feet, or almost 6.6
miles deep. The deeper you
go in the ocean water column
the colder the water
temperature gets and the
greater the pressure becomes.
The pressure at this depth is
very great. Humans have only
visited here one time, in 1960,
and had to leave in a hurry
after the window on their
submarine started to crack
because of the pressure.
The Ocean Floor
What is going on at the Marianas trench?
The oceanic plate or in this case the fast-moving pacific plate, plunges
downward toward the mantle, while the continental plate or the
Philippine Plate, rides up over the top. The forces driving the two
plates together are really intense, so the underlying oceanic plate
creates a trench where it drags the edge of the continental crust
down as it descends underneath.
Now let’s observe a demonstration of water pressure.
The Deep Ocean Floor
The abyssal plain which is out beyond the continental slope is a nearly
flat region of the ocean floor covered with thick layers of sediment.
Sometimes there are volcanic mountains that have built up enough
lava to break the surface. These are volcanic islands.
Sometimes the mountains are not tall enough yet to break the surface.
These are called seamounts.
Some volcanic islands called guyots have eroded so much that their
tops are now below sea level.
Overfly of New Zealand and surrounding ocean floor
Assessment
Use the word bank to complete the major features.
shallow
animal
begins
subduction
nearly flat
plant
drops off
sea-floor spreading
sediment
continental slope
Major Features
Continental Shelf- The continental shelf is _______________ and extends outward to the
____________________________ _______________________.
This region contains the highest amount of ____________________ and_________________ life.
Continental Slope- The continental slope ______________ where the bottom of the ocean sharply
______________ __________ into a steep slope.
Abyssal Plain-The abyssal plain which is out beyond the continental slope is a_____________
______________ region of the ocean floor covered with thick layers of___________________.
shallow
animal
begins
subduction
nearly flat
plant
drops off
sea-floor spreading
sediment
continental slope
Mid-Ocean Ridge- At the mid-ocean ridges ____________ - ______________
_________________ causes the ocean to grow wider.
Deep-Ocean Trenches- ____________________________ causes the deep ocean
trenches to develop on the ocean floor