Geography Reference
In-Depth Information
Figure 3.1
The interior of the Earth.
Note
The schematic diagram is not drawn to scale.
oceans and that there are valleys in the middle of these mountain
ranges. It was also found that the deepest parts of the oceans are
located very close to the edge of the ocean rather than in the
middle. The ocean floor was found to have 'magnetic stripes'. It is
known that the Earth's magnetic field reverses every few hundred
thousand years and the direction of the poles is recorded at the
time when volcanic lava forms and cools. Alternating north or
south-facing magnetic stripes occur right across the oceans and are
orientated parallel to the mid-ocean mountain ridges showing that
the ocean floor had formed at the mid-ocean and then moved
slowly away on either side of the mid-ocean towards the conti-
nents. This provided the first real evidence that large masses of rock
on Earth can slowly drift.
