Friday, March 14, 2008

shaping of the earth from tectonic plates

Plate Tectonics

Question: Explain how the movement of the tectonic plates shapes the earth using specific examples.

Response: There are many reasons why the earth is shaped why it is, but the two main reasons are heat and pressure. Heat is one of the leading causes of the formation of the earth. Heat helps form the earth by convection. Seawater, groundwater in the crust, and different magmas help convection. Most of the earths heat is generated from the decay of long-lived radioactive isotopes. As potassium, thorium, and uranium are concentrated in the upper continental crust, the heat produced by their decay accounts for 40% of the average continental heat flow.
The three main types of continental crusts are exposed continental shield (cratons), continental platforms, and mountain belts.
The ocean floor has many plates as well. The oceans crust tends to move away from mid-ocean ridges. Mid-ocean ridges transect the major basins of the world and are active sights for generating new crust from magmas rising from the mantle below from the linear fractures. The ocean floor is found at the ocean margins. Some of the known ocean rocks (oldest found) are only 200 million years old while most others are only 100 million years old. Some of the lowest heat flows are on old ocean floors and trenches, and in rapidly subsiding basins on the continental crust.
Pressure is another factor. The main pressure on the earth comes from the weight of overlying rocks and sub ducted plates. The standard unit for (Pa) is (1 atm=101 325Pa.). Mantle rocks have higher density, which further increases downward pressure.


1 comment:

Anonymous said...

great info loved reading it -CG5