Transcript The Ocean Floor

The Ocean Floor
Chapter 13 Section 2
Studying the Ocean Floor
Sonar- used on ocean surface
Satellite- Seasat and Geosat- used in
space
Sonar
Sound Navigation and Ranging
Scientists send sound waves to the bottom
of the ocean by ship.
The sound waves bounce off the ocean
floor and return to the ship.
The deeper the ocean , the longer it takes
for the sound waves to return.
SONAR-FYI
Measuring Water Depth
Today's oceanographers use sonar instruments
to generate a sound signal that is bounced or
"echoed" off the sea floor and then recorded on
board the ship. The speed of sound in water is
1,500 m per second, four times faster than the
speed of sound in air. By carefully measuring the
round-trip time of the sound waves and taking
into account the variables of temperature and
salinity, the depth of the water and the distance
to another object can be measured accurately.
Seasat
Satellites send images to Earth that
measure direction and speed of ocean
waves
Seasat-1978
Geosat- Navy Satellite
Military satellite
Measures height of the
ocean surface.
Different underwater
features affect the
height of the water
above them.
The Ocean Floor
Continental shelf
Continental slope
Continental rise
Abyssal Plain
Mid-ocean ridge
Rift valley
Ocean trench
Seamounts
You do not have to write
all of these, just make
sure they are your
headings.
Continental shelf A
Continental slope B
Continental rise C
Abyssal Plain E
Mid-ocean ridge F
Rift valley F
Ocean trench H
Seamounts D/G
AA
BC
D
E
F
G
H
Continental Margin
Made up of:



Continental shelf
Continental slope
Continental rise
Continental Shelf
Begins at the shoreline
Continues until the ocean floor starts to
slope
Depth can reach about 200 meters
Continental Slope
Begins at edge of continental shelf
Continues down to the flat part of the
ocean floor
Ranges between 200 meters to about
4000 meters
Continental Rise
Base of continental slope
Made of large piles of sediment
Deep Ocean Basin
Made up of:





Abyssal plain
Mid-ocean ridge
Rift valleys
Seamounts
Ocean trenches
Abyssal Plain
Large, flat area of the ocean floor
Covered in mud and remains of tiny
marine organisms
Average depth 4000 meters
Abyssal
Plain
Mid-Ocean Ridge
Underwater mountain ranges
Form where tectonic plates pull apart
Rising magma between the plates creates
the ridge
Mid-Ocean Ridge
Rift Valley
Zone between the plates
In the rift valley, which can be 15 to 30
miles (24 to 48 kilometers) wide, new
oceanic crust is being made, which means
lots of seismic activity is happening.
Hydrothermal vents were discovered in rift
valleys.
Rift Valley
Ocean Trench
Huge cracks on ocean floor
Created by oceanic plate pushing beneath
continental plate or another oceanic plate
Deep-sea trenches are the deepest parts of the
ocean.
The deepest one, the Marianas Trench in the
South Pacific Ocean, is more than 35,000 feet
(10,668 meters), or almost 6.6 miles (10.6
kilometers) deep.
A Navy-owned submarine, the Trieste, still holds
the record for diving to the bottom of the deepest
part of the Marianas Trench, the Challenger
Deep, on January 23,1960.
Bioluminescence
Scientists estimate that 90 percent of
deep-sea species are bioluminescent .
Bioluminescence is the production of
visible light by living organisms.
Seamounts
Mountains of volcanic material
Formed when magma pushes it way
through or between tectonic plates
If seamounts build up they can become
volcanic islands; Example: Hawaiian
Islands
Seamounts are usually 25 miles (40
kilometers) in diameter and can be 10,000
to 15,000 feet (3000 to 4500 meters) tall.
Seamounts
Less than 0.1 percent of the world's seamounts
have been explored to learn what species live
on them, but many of the species that have been
found so far are new to science.
It has been estimated that more than 30,000
seamounts reaching more than 1,000 meters tall
are found in the Pacific Ocean. Approximately
800 are in the Atlantic Ocean, and an unknown
number exist in the Indian Ocean.
They usually have volcanic origins.
Alvin
Alvin, the world's first deep-sea
submersible
Three-person, self-propelling capsule-like
submarine nearly eight meters long.
Alvin has an operational maximum depth
of about 4,000 meters.
Shinkai 6500- Japan
Shinkai 6500, a Japanese research
submarine built in 1989, can work at
depths down to 6,400 m.
World's deepest-diving manned research
submarine.
Quiz
1. The Hawaiian Islands form from what type of ocean
feature?
2. Where is pressure the greatest or the most intense?
3. What is sonar?
4. Underwater mountain range?
5. Underwater volcano?
6. Feature of the ocean that is at the edge of a
continent?
7. Production of visible light by an organism?
8. Besides organisms in the ocean, what other organism
can you think of that produces visible light?
9. The flat part of the ocean floor?
10. What makes up the continental margin?
11. What makes up the deep ocean basin?
12. Where do tectonic plates pull apart or move away
from each other?
13. Deepest part of the ocean?
Answers
1. seamount
2. at the bottom of the ocean
3. Sound navigation and ranging- scientists send sound
waves to the ocean floor and measure the time it takes
for the sound waves to return
4. mid-ocean ridge
5. seamount
6. Continental shelf
7. Bioluminescence
8. fireflies/lightning bugs
9. abyssal plain
10. continental shelf, continental slope and continental
rise
11.abyssal plain, mid-ocean ridge, rift valley, Ocean
trench and seamount
12. Mid-ocean ridge
13. Ocean trench
The Ocean Floor
The continents lie on the continental plates. The edges of these plates are under
water, and they form the continental shelves. These shelves slope outward very
gently towards the ocean depths. In some places these shelves go out a long way, up
to 900 miles: In other places the shelves are much narrower. These shelves are fairly
smooth because debris from the land is falling onto them from the water. This debris
contains nutrients washed down from the land, and these nutrients, plus the shallow
water, contribute to the abundance of life forms near the continents.
Where the continental shelves end, there is a steep drop downwards. This is
called the continental slope. It plunges down into the dark, cold waters of the ocean.
At the bottom of the continental slope there is a an area that slopes gradually
downward to blend into the abyssal plain. This is the bottom of the ocean as we think
of it.
The ocean floor seems like a different world. There is no sun light down here. The
water is very cold. The pressure of the weight of miles of water above this area would
easily crush a submarine. Tiny flecks of material from the sunlit world float downward
and eventually settle on the bottom. There is almost nothing to eat, and the animals
that live here are few and far between. There are many different kinds of animals, but
they are small and widely scattered. They are able to survive on very little.
However, it is not all silence and darkness here. The earth's crust is thinnest in the
ocean basins, and volcanic eruptions are part of this environment. Here and there
isolated peaks called sea mounts rise above the flat abyssal plain. However, the most
active part of deep ocean geology occurs in the deep sea trenches, where the ocean
floor is spreading apart. Lava comes up through the fissures, building up mountains
and deep sea vents, called smokers. The constantly up-welling lava pushes the sea
floor away from the trenches and out towards the continents. When the sea floor
reaches the continental plates, it subducts, or slides underneath them, carrying the
cold rocky floor back into the hot mantle of the earth.