Transcript The Ocean Floor


The ocean floor has similar features to the surface
of the Earth where we live.
◦ Mountains, valleys, volcanoes
◦ The features of the ocean floor are very big, with deep
trenches and tall mountains – it sort of looks like a
rollercoaster.

Scientists have used echo sounding to figure
out the topography of the ocean floor
◦ Topography is the surface of land. In this case we
are taking about the land beneath the ocean.

Gently sloping shelf of land extending from the
shoreline to the continental edge


A sharp underwater hill that connects the
continent to the ocean
The way the continental slope looks matches
the continental shelf
◦ If the continental slope is rocky, the continental
shelf is rocky too
Check for
Understanding:
What would the
continental shelf
look like if the
continental slope
was smooth?


A gently sloping hill that connects the continental slope
to the ocean floor. (This is where you are no longer on
the continent)
The continental rise is created by the deposition of
sediments
◦ The height of the continental rise can increase if a storm or
intense waves cause a lot of erosion and deposition!


A steep V-shaped canyon that cuts through the
continental shelf and continental slope.
Some submarine canyons are bigger than the Grand
Canyon!!


The flat smooth part of the deep ocean floor
Extremely dark – no sunlight can reach here!
◦ Challenge: What do you think this means for plants?


Valleys cut deep into the ocean floor.
This is the deepest part of the ocean floor.


A steep, pointy extinct volcano.
Basically it is a tall underwater mountain.


A seamount that has a flat top
The top is flattened by the
action of waves

An undersea mountain range.
 DO YOU remember how this is formed??

A deep valley in a mid-ocean ridge that is formed
when the sea floor is pulled apart.
 WHAT CAUSES THE SEAFLOOR TO SPREAD APART??
riftvalley is
IN the
midocean
ridge

http://www.classzone.com/books/earth_scie
nce/terc/content/investigations/es2301/es2
301page03.cfm?chapter_no=investigation


Because it is
impossible to see the
sea floor, scientists
use a technique called
echo sounding
Echo Sounding is how
long it takes a sound
wave to go from a
ship to the sea floor
and back to the ship
Videos:
http://www.youtube.com/watch?v=yFu2676bc6g
http://player.discoveryeducation.com/index.cfm?guidAssetId=4F6C5
920-9267-41B4-9DA01C532229B567&blnFromSearch=1&productcode=US
Check for understanding: in 1-2 COMPLETE
sentences—summarize what sound echoing or
sonar echoing is and what is it used for.

Check for understanding: Which ocean is the
deepest ocean?

Sound waves travels 1,520 m/s in sea water.


So, if a pulse of sound waves makes a round trip in
2 seconds, then it has traveled 1,520 meters to the
bottom of the ocean & back up to the surface.
To find the depth of the ocean at any point,
scientists measure the time of the round trip in
seconds, multiply that by 1,520 m/s and then
divide that by 2.
Questions:
1.
Waves (pings) from an
echo sounder aboard a
ship make a round trip in
8 seconds. How far
beneath the ship is the
ocean floor?
2.
Another ship records
waves (pings) that make
a round trip in 20
seconds. How far
beneath the ship is the
ocean floor?
Answers:
1. _____________
2.
_____________



We are going Magic
School Bus style—
down to the bottom of
the ocean.
We are going 9,00010,000 meters into
the ocean to see the
ocean floor!
What kind of scary sea
animals will we run
into?
In pairs calculate the depth
of each creepy crawly
ocean animal to find out
which animals we will be
swimming with.
A scientist sends out Sound wave A that takes
9 seconds to echo back. A second sound wave
B takes 14 seconds to echo back.
◦ Which sound wave hit a deeper part of the ocean?
(circle one)
A
or
B
◦ Which sound wave (A or B) found an Abyssal Plain?
__________________
◦ Which sound wave (A or B) found a Ocean Trench?
____________________