The Sea Floor
Brain Warmers:
• Q: Of the Northern and Southern Hemisphere,
which one contains the most water??
• A: Right! The Southern Hemisphere contains
nearly 80% water by volume.
• Q: Which ocean is the largest? The deepest?
a. Arctic b. Pacific
• A: Pacific
• A: Pacific again!
c. Atlantic d. Indian
Figure 2.02
How did it all get this way?
• Big bang leftovers!
• Density played a major role.
• How’s that work??
• Density = mass/volume
• Lighter stuff stays on the top!
Figure 2.03
Ocean Floor Facts
• Ocean crust is composed of basalt. Basalt is
common to the sea floor also.
• Much of the crust which forms land masses is
composed of granite.
• Much of the ocean floor and crust differs in
age too! (200 myo compared to 3.8 byo!!)
• Why??
About what percent of the Earth’s
surface is covered by ocean?
25%
25
%
25%
85
%
25%
71
%
25%
50
%
A. 50%
B. 71%
C. 85%
D. 25%
Which is true?
A. The Pacific ocean is deepest and smallest
B. The Arctic ocean is shallowest and smallest
C. The Atlantic ocean is deepest and largest
D. The Indian ocean is shallowest and largest
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25% 25% 25% 25%
Ocean Floor Structure
• Sir Francis Bacon (1620) considered
continents puzzle pieces.
• Geological features (coal deposits) matched on
opposite coasts.
Figure 2.04
Ocean Floor Structure
• Sir Francis Bacon (1620) considered contents
puzzle pieces.
• Geological features (coal deposits) matched on
opposite coasts.
• Alfred Wegner (1912) hypothesized
continental drift.
180 mya
Pangea Bound…
• Continents may have been one
piece which later broke apart,
moved, and formed present
day conditions.
150 mya
95 mya
• How??
• Plate tectonics ocean floor
movement.
• Consists of faults (cracks)
which form the mid ocean
ridges (mountains).
45 mya
15 mya
Figure 2.05
Current Mid-ocean ridges & trenches
http://www.youtube.com/watch?v=K8blL9Ki2mQ
Figure 2.06
These locations are a significant source of geological activity!
http://www.youtube.com/watch?v=v5DG5Eup9ss
Figure 2.07
http://www.youtube.com/watch?v=hmMlspNoZMs
Figure 2.08
• Sea floor spreading occurs at
mid-ocean ridges.
• Magnetic anomalies occur here too!
“Okay, Miss Collins. You’re using
big words again!!”
Magnetic anemone!! But seriously….
•Sea-floor spreading
where the ocean floor
moves away from
the mid-ocean ridge
records the magnetic
fields of the earth.
Figure 2.10
Locations and direction of seafloor spreading.
Figure 2.11
Crust and mantle come together to form the lithosphere.
Subduction, and resulting subduction zones, are where ocean floor
plates flow beneath the mantle of the crust and are places of tectonic
activity.
Figure 2.12
Trenches and island arcs can be formed when two sections of ocean
plates come together.
Figure 2.13
Mt. Veniaminof, Alaska
Some areas can be quite acitve!!
Figure 2.14
When plates move
sideways then there is a
new formation called a
shear-boundary.
San Andreas Fault, CA
Figure 2.15
Swirling vs. Pulling
Convection suggests that continents move on a “soup” of rock,
whereas slab pulling indicates that as rock cools, it sinks beneath
the surface and “pulls” lithosphere into the depths (This is the
currently accepted explanation.)
Magnetic anomalies are bands of rock that
run parallel to the mid-ocean ridge system.
What do they provide evidence for?
an
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A. Bacteria lived in the ocean
floor millions of years ago
B. Volcanoes form at ocean
ridges.
C. The sea floor was formed
in layers
D. Granite is denser than
basalt
.. .
25% 25% 25% 25%
Continental plates are believed to move
because of which of these causes?
...
d
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Ne
A. New volcanic rock pushes
them away from spreading
centers.
B. Cooling lithosphere becomes
dense, sinks, and pulls a
plate with it.
C. Plates crack along fault lines.
D. The mantle is fluid and
carries plates along with it
Figure 2.17
Ocean sediments often preserve organism which help
scientist age the ocean floor.
Lithogenous sediment contains minerals, while biogenous
sediment contains fossil remains.
Figure 2.19
Figure 2.20
Figure 2.21
Figure 2.22
Figure 2.23
Figure 2.24
The biologically richest area of the
seafloor is
A. The continental
shelf.
B. The continental
slope.
C. The plain.
D. Deep-sea vents.
E. The abyssal plain
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Red clay is an example of
biogenous sediment.
Tr
50%
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50%
Fa
l
A. True
B. False
A swimmer sees a shark. Some sharks are
dangerous. The swimmer swims away from
the shark based on this information.
25% 25% 25% 25%
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A. Tested a hypothesis
B. Used inductive reasoning
C. Formed a theory
D. Used deductive reasoning
Which of the following is a valid
scientific hypothesis?
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A. Dogs are superior pets.
B. It is immoral to keep
whales in captivity.
C. Dolphins use brainwaves
to communicate.
D. One-spot foxface rabbitfish
prefer green algae to red
algae.
Figure 2.25
http://www.youtube.com/watch?v=GyMLlLxbfa4
Figure 2.26
Figure 2.27
Text Art 2.01
http://www.youtube.com/watch?v=9md0q29ED5w
Text Art 2.02
http://www.youtube.com/watch?v=zRfaZqeehc0
http://www.youtube.com/watch?v=W2qdlYkl2HY