The Active
Earth
How do geological processes
change the planet?
Continental Drift
Continental Drift is
the action of
convection currents
in the Asthenosphere
on the continental
plates causing them
to move small
distances over long
periods of time in
relation to each
other.
Evidence for Continental Drift
Mid ocean ridges
Matching continental margins
Magnetic striping of ocean floor rocks
Corresponding rock types on
continental margins.
Continental Margins
The edges of the continents line
up with each other showing that
they were once joined together.
This is shown in the image
opposite where South America
and Africa’s edges line up
together. Continental Margins
Plate Tectonics
Deep within the earth
molten rock moves up
towards the surface.
When it strikes the
bottom of the tectonic
plates it spreads out
horizontally. This
pushes on the
underside of the plate
causing it the plate to
move as well. This
continual flow of
molten rock is called a
convection current.
Mid Ocean Ridges
Where the oceanic plates meet, the
molten rock pushes its way to the
surface. This causes the edges of
the plates to move away from each
other, and new rock solidifies on
the edge to form new ocean floor.
This process forms Mid- Ocean
Ridges.
Magnetic seafloor striping
As molten rock makes its way to the
surface the iron contained within the rock
is magnetised to the current direction of
the earth’s magnetic field. As the rock
cools and solidifies the direction of the
magnetic field is locked into the rocks
recording any changes in the earth’s
magnetic field. On either side of the
mid ocean ridges the rocks have the
same pattern of magnetic arrangement.
It is identical as you move out away from
the centre.
Magnetic seafloor striping
Corresponding rock types and
fossils on Continents
The rocks on the
edges of continents
have the same
composition and the
same fossils. This
indicates that they
were once joined
together and have
separated over time
to the current
positions of the
continents. Scientific arguments
Were the continents joined
together?
The rocks on the
edges of continents
have the same
composition and the
same fossils. This
indicates that they
were once joined
together and have
separated over time
to the current
positions of the
continents. Scientific arguments
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