Chapter 2 – Plate Tectonics
Part 1
er 2
The
Sea
Figure 2.01
71% of the earth’s surface is water. Two thirds of
earth’s crust is in the northern hemisphere. 80% of
the southern hemisphere is ocean.
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.
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!
Figure 2.03
The inner core is 4000°C 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.
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. 1960’s geologists
agree the continents do move. Plate tectonics
Figure 2.05
Earthquakes indicate plate boundaries.
Figure 2.06
World War II sonar mapped seafloor, and found many
features like mid-ocean ridge and trenches.
Figure 2.07
Deep earthquakes indicate crust is being destroyed and
shallow earthquakes indicate seafloor spreading.
Figure 2.08
Magnetic reversal shows newest crust is in the middle of
the ocean.
Figure 2.09
Rift is where earth is seperating, causing seafloor
spreading – Divergent boundary- fig. 2.9-Know!
Figure 2.10
Earthquakes indicate plate boundaries
Figure 2.11
Ocean/Continental convergent plate boundary. Subduction
zone – deep earthquake – trench/mountains
Figure 2.12
Ocean/Ocean convergent plate boundary. Subduction
zone – deep earthquake – trench/island arc.
Figure 2.13
Mount Veniaminof - Aleutian Island Arc