Chapter 2

1
Chapter 2 Plate Tectonics

• Part 1

2
Chapter 2The Sea Floor
3
Figure 2.01
71 of the earths surface is water. Two thirds
of earths crust is in the northern hemisphere.
80 of the southern hemisphere is ocean.
4
Figure 2.02
Traditionally four ocean basins Pacific,
Atlantic, Indian, and Artic but one real ocean.
The water that surrounds antarctica is referred
to as the southern ocean. connected to the oceans
are Mediterranean Sea, Gulf of Mexico, and South
China Sea.
5
Early earth was molten and the densest material
was pulled to the center of the earth by gravity.
differentiation The earth slowly cools, thin
crust hardens and water condenses into liquid.
The earth just happens to be the right distance
from the sun. No water no life!
6
Figure 2.03
The inner core is 4000C and made of nickel and
iron. It has one million times as much pressure
as the surface of the earth. The outer part of
the mantle is plastic and can flow, the
asthenoshere. Ocean and continental crust float
on top. Ocean crust is thinner and more dense,
mostly basalt.
7
Figure 2.04
Once world map started taking shape, scientists
noticed that Africa and South America fit
together like puzzle pieces. Coincidence?
Alfred Wegener hypothesised that continents
drifted apart. 1960s geologists agree the
continents do move. Plate tectonics
8
Figure 2.05
Earthquakes indicate plate boundaries.
9
Figure 2.06
World War II sonar mapped seafloor, and found
many features like mid-ocean ridge and trenches.
10
Figure 2.07
Deep earthquakes indicate crust is being
destroyed and shallow earthquakes indicate
seafloor spreading.
11
Figure 2.08
Magnetic reversal shows newest crust is in the
middle of the ocean.
12
Figure 2.09
Rift is where earth is seperating, causing
seafloor spreading Divergent boundary- fig.
2.9-Know!
13
Figure 2.10
Earthquakes indicate plate boundaries
14
Figure 2.11
Ocean/Continental convergent plate boundary.
Subduction zone deep earthquake
trench/mountains
15
Figure 2.12
Ocean/Ocean convergent plate boundary.
Subduction zone deep earthquake trench/island
arc.
16
Figure 2.13
Mount Veniaminof - Aleutian Island Arc