004-Plate Tectonics - lithosphere asthenosphere mesosphere...

asthenosphere
lithosphere
mesosphere

Lithosphere (hard)
Asthenosphere (soft)
Mesosphere

Mantle - 1000
o
C
mesosphere
•
Solid
•
~ 2300 km thick
asthenosphere
•
Soft
•
~3000 km thick
lithosphere
•
hard
•
~100 km thick
Inner Core- 4300
o
C
•
mostly iron core
•
inner part is so compressed that it is solid
Outer Core- 3700
o
C
•
iron and sulfur
•
liquid
Crust
•
floats on top of lithosphere
continental crust (granite)
•
20 to 70 km thick
oceanic crust (basalt)
•
~ 8 km thick
Earth formed 4.6 bya

Principles of plate tectonics
•
The Earth is composed of a mosaic of thin
rigid plates (pieces of lithosphere) that move
horizontally with respect to one another
•
Plates interact with each other along their
plate boundaries
•
Plate boundaries associated with tectonic
activity (mountain building, earthquakes,
active volcanoes)

Alfred Wegener
•
Proposed Theory of Continental Drift (1915)
•
Failed to provide a mechanism

Evidence for Continental Drift
•
continental shape
•
similar geology
•
fossil evidence (animal and plant)
•
volcano and earthquake zone
•
paleomagnetism