of the earth
studying plate-tectonics the best starting point is examining
of the earth. The earth is very similar to a peach in its
structure. In the centre is a solid core.
Surrounding the core is the inner
core, then the mantle,
which is covered in the earths 'skin' or crust.
Drift and Plate Tectonics
Wegener published a theory to explain why the Earth looked
like a huge jigsaw. He believed the continents were once joined
forming a supercontinent he called Pangaea.
Over 180 million years ago this supercontinent began to "break
up" due to continental drift.
During the 20th Century, scientists developed the theory of Plate
Tectonics. The theory suggested that the crust of the Earth
is split up into seven large plates (see map below) and a few
smaller ones, all of which are able to slowly move around on the
Earth's surface. They float on the semi-molten mantle rocks, and
are moved around by convection currents within the very hot rocks.
The are two types of tectonic plates - continental
plates and oceanic
The point where two or more plates meet is known as a plate
boundary. There are four main types of plate boundary. These
are constructive, destructive, conservative and collision margins.
/ Constructive (divergent
) plate boundaries
plate boundaries occur when two plates move away from each
American and Eurasian Plate
/ Destructive (subduction
zones) plate boundaries
plate boundaries occur when an oceanic plate is forced under
(or subducts) a continental plate (diagram).
Plate and the Eurasian Plate
(transform faults) plate
plate boundaries occur when two plates slide past each other.
American Plate and the Pacific Plate
plate boundaries occur when two continental plates move towards
and the Eurasian Plate