Transcript The Sea Floor

The Sea Floor
Brain Warmers:
• Q: Of the Norhern 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??
Ocean Floor Structure
• Sir Francis Bacon (1620) considered contents
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 appart,
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
Figure 2.06
These locations are a significant source of geological activity!
Figure 2.07
Figure 2.08
• Sea floor spreading occurs at
mid-ocean ridges.
• Magnetic anomalies occur here too!
“Okay, Dr. K. 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 where ocean floor
plates flow beneath the mantle of the crust 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 a new
formation called a
shear-boundary.
San Andreas Fault, CA
Figure 2.15
Swirlling vs. Pulling
Convection suggests that continents move on a “soup” of rock,
Whearas slab pulling indicates that as rock cools, it sink beneath
the surface and “pulls” lithosphere into the depths (This is the
currently accepted explanation.)
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
Figure 2.25
Figure 2.26
Figure 2.27
Text Art 2.01
Text Art 2.02