Transcript Continental Drift and Plate Tectonics part 1

Plate Tectonics and
Continental Drift
Plate Tectonics
• The surface of the Earth is composed of about a
dozen major rigid, moving crustal plates and several
smaller plates
•Plates
a. Slabs of Earth’s lithosphere (crust and upper
mantle)
b. Average thickness is 100 km (62 miles)
c. Most plates support both continent and
ocean
Continental Drift
states that the continents have drifted and still are
drifting apart
Why do the plates move?
1. Due to tremendous heat, rock in the
asthenosphere is like hot taffy
2. This allows plates to ride on top of hot, flowing
rock.
3. Plates move because heat is being released
from deep inside the earth.
4. Convection currents causes hot material to
rise and expand (plates diverge) and cooler
material to sink and contract (plates converge).
Continental Drift
_________
Wegener
proposed the
theory that the
crustal plates are
moving over the
mantle. This was
supported by
fossil and rock
type evidence;
also matching of
coastline shapes.
Convection Currents
The force responsible for plate movement is __________.
Plate Boundaries
The following two slides show maps of
the current major plate boundaries
and their relative motions.
 You should be able to describe
various landforms created by different
plate movements.
