Download oceanfloor - Home | eaecaoceans11.srsbteachers.ednet.ns.ca

Topography of the Ocean
H.M.S. Challenger
• Topography refers to the shapes of the ocean
crust.
• In this session you will learn the different
surface features of the ocean floor along with
their names.
• Describe the various physiological features
associated with the ocean basins.
5/23/2017
2
What factors affect the topography of the
Earth’s crust after its formation?
Natural Factors
Artificial Factors
• Moving Air
▫ Wind
• Human Activity
▫ Agriculture
 Moves particles too
▫ Tornadoes
• Moving Water
▫ Rain (storms)
▫ Flooding
▫ Wave action
▫ Currents
• Geologic Factors
▫ Earthquakes
▫ Volcanoes
 Land Management
 Land Sculpting
▫ Industrial
 Mining/Resource Retrieval
 Factories
▫ Commercial
Rift Valleys
Mountain Building
Subduction Zones
 Road/Bridge Building
 Land Development
 Housing
 Shopping
Earth Beneath the Sea
• The H.M.S. Challenger was one of the first ships to do
extensive oceanic studies.
• The echo sounder was an innovation that allowed for a
lot of research to be able to be conducted about the
ocean's floor.
• Here is a problem:
▫ Sound travels 5000 ft. per second through water.
▫ It takes one second for the echo to go
from the ship and then be bounced off
the bottom and return to the ship.
▫ The total distance is 5000 feet, so you know
from the ship to the ocean floor it is half of that,
or 2500 feet.
▫ The formula 1/2(5000)(time traveled)
can be used anytime.
• The Earth’s crust can be divided into two parts:
▫ Continental crust
▫ Oceanic crust
• Ocean basins can be divided into two regions:
▫ continental margins
▫ deep ocean basins
•Continental Margin which is
made up of:
▫Continental Slope
▫Continental Rise
▫Continental Shelf
5/23/2017
6
Features of the Deep Ocean Basin
•Abyssal Plains
•Ridges
•Seamounts and Guyots
5/23/2017
7
Vocabulary
• Continental Margin – the part of our continent
that extends into the ocean.
▫ Continental shelf – a slow drop in the ocean floor
beginning at the coast line.
▫ Continental Slope – starting at the outer edge of
the continental shelf the continental slope drops off
steeply toward the ocean floor.
▫ Continental Rise – the area of the ocean floor that
extends between the continental slope and the deep
ocean floor.
5/23/2017
9
Continental Margins
• Made up of three distinct regions, the Continental
Shelf, Continental Slope, and Continental Rise.
• Mostly made up of sediments that have been
washed off of land.
• Considered to be part of each continent’s land mass.
5/23/2017
10
Continental Shelf
• A gently sloping surface (less than one tenth of a
degree) that begins at the shore line and extends to
the beginning of the Continental Slope.
Continental Shelf (continued)
• It is primarily made up of sediments that have been
carried down rivers.
 Numerous hills, terraces, canyons
 The width of the Continental Shelf varies. Scientists claim
the average width is about 65 km.
Submerged part of the continent
Locally cut by canyons formed by currents and moving
sediment
Submarine Canyons and Turbidity Currents
Submarine canyons, steep walled underwater valleys,
are created by turbidity currents. Click on the links
to learn more about them.
Continental Slope
• A fairly steep drop that separates the Continental
Shelf from the Continental Rise.
▫ Between the shelf and the floor and deep ocean
▫ Boundary between continental and oceanic crust
• Slopes an average of 2-3 degrees
▫ 50 degrees off volcanic islands (much steeper!)
• It is made up of the same sediments as the
Continental Shelf.
Continental Rise
•Less steep than Continental Slopes.
• Made of sediment deposited at the boundary
between the continental slope and the abyssal plain.
•The width of the Continental Rise ranges from a few
kilometers to hundreds of kilometers.
The Ocean Basin Floor
• 30% of the Earth's surface are made up by these
landforms:
▫ Deep ocean trenches, where 2 converging plates meet,
are the deepest regions of Earth. The Marianas trench
can reach up to 36,000 ft. deep.
▫ Abyssal plains are very flat regions made of the sediment
carried by turbidity currents.
▫ Seamounts are isolated volcanic peaks made by
hotspots, like Hawaii. Others are near ocean ridges.
Others emerge as land, like St. Helena.
A Deep Ocean Trench
Abyssal Plain
Flat, deep ocean floor.
Depth may be
3,000–6,000 m
or more
Thick accumulations
of sediment
The Topography of an Abyssal Plain
Location of some Seamounts
around the globe
Vocabulary (continued)
• Ridges – the ocean floor has ocean basins in it.
Each basin has mountain ranges just like the
mountain ranges on land. Underwater mountain
ranges form ridges that look like long peaks.
• Seamounts – volcanic mountains that rise more
than 1,000 meters above the ocean floor. Hawaii is
a seamount.
• Guyots – volcanic mountains that have been
flattened by wave action and now are totally
underwater.
5/23/2017
21
Mid Ocean Ridges
• This is where sea floor
spreading occurs, and new
crust is formed.
• These regions make up to
20% of the Earth's surface
▫ They run a course of 40,000
miles around the Earth that
looks like a baseball seam.
• Click here to learn about the
Mid-Atlantic Ridge (below,
the MAR is on land in
Iceland)
Undersea Volcanoes
Thick, black smoke billowed miles into the sky
Scorching, red lava oozed from a turbulent sea
Molten lava hardened into pumice and cinder
Island of Surtsey emerged near
Iceland, 425 feet below the ocean
Seamounts
• Seamounts and Guyots are both individual
volcanic mountains on the ocean floor
• Distinct because seamounts tend to be
circular or conical
•The difference between seamounts and
guyots  Guyots have
been flattened and are below
the ocean surface.
•Some seamounts do not
reach the ocean surface
either.
Guyot
Flat-topped seamount rising from ocean
floor like a volcano but planed off on
top and covered by appreciable water
depth.
Guyot Formation
Coral Reefs and Atolls
• Coral reefs are made of skeletal remains from
coral polyps and algaes.
• They live in warm waters, above 75 degrees F
anually.
• The H.M.S. Beagle expedition
did research on atolls and their
locations.
• Atolls are islands made out
coral.
of
Atolls
• A coral reef that formed around an undersea
volcano which has since been eroded by wind and
waves.
Resources
• Plate Tectonics