A PowerPoint illustrating what continental drift is and who helped to discover it.

2. Definition
 The very slow movement of the continental plates on the
surface of the Earth due to tectonic activity through
geological time.

3. What is the evidence of Continental Drift?
 Continental Fit
 Some continents such as the Western seaboard of Africa and
the Eastern seaboard of South America seem to fit together as if
placed beside each other.

4. What is the evidence of Continental Drift?
 Geological evidence
 Rocks of the same age and type and
displaying the same formations are found
in south-east Brazil and South Africa.
 The trends of the mountains in the eastern
USA and north-west Europe are similar
when placed in their old positions.
 Similar glacial deposits are found in
Antarctica, South America and India, now
thousands of km apart.
 Striations showing the same orientation
when the continents are reunited, are
found in Brazil and West Africa.
 Striations means a series of ridges, furrows or
linear marks, and is used in several ways

5. What is the evidence of Continental Drift?
 Climatic evidence
 Parts of Antarctica, North America and
the UK all contain coal deposits of
similar age that were formed in tropical
conditions.
 These areas are no longer in tropical
climates which suggests that they have
drifted apart since the Carboniferous
period.
• Glacial Striations (scratches in the
rocks) can be found that match in
Brazil and West Africa
• Glacial deposits are also very similar in
India, South America and in the Vaal
Valley in South Africa
• These landmarks suggest that although
these areas are very far apart now they
once had a very similar climate

6. What is the evidence of Continental Drift?
 Biological evidence
 Similar fossil formations are found on either side of the
Atlantic. For example, a reptile called Mesosaurus, is found
only in South America and Southern African sediments.
 These are dated from the Permian age (aprox. 280million years ago).
 Plant remains from the humid swamps that later formed coal
deposits have been found in India and Antarctica.
 Marsupials are found only in Australia because it
drifted away from the main supercontinent before
the predators that wiped them out elsewhere had
migrated there.

8. What is the evidence of Continental Drift?
 Paleomagnetism
 This is when hot magma rises to the earth's surface and cools, the minerals themselves
become magnetized.
 Rocks formed in different places on the planet are magnetized differently.
 When rock layers were discovered with different magnetism than the original rock, it
points to continental drift.
 The Mid Atlantic Ridge was the first piece of evidence to support Wegener’s Theory.
 2 British Geologists, Vine and Matthews, discovered magnetic stripes or banding running
parallel to the ridge in the 1960s.
 These stripes corresponded to times when the Earth’s magnetic field reversed from North
to South and so on, and iron particles in the erupting magma either side of the ridge
cooled and aligned themselves with the Earth’s polarity at that time.
 These symmetric stripes supported a theory by Hess on sea floor spreading, which we
now know exists at the Ridge. In addition, by studying the stripes rates of spreading could
be calculated.
 This has been further supported by studies of the ages of rocks either side of the ridge.
Rocks closest to the ridge are youngest (up to 10 million years old) and those furthest away
are oldest (over 156 million years old) on both sides of the ridge.

11. Theory of Continental drift
 In 1915, the German geologist and meteorologist Alfred Wegener first proposed
the theory of continental drift, which states that parts of the Earth's crust slowly
drift atop a liquid core. The fossil record supports and gives credence to the
theories of continental drift and plate tectonics.
 Wegener hypothesized that there was a gigantic supercontinent 200 million
years ago, which he named Pangaea, meaning "All-earth".
 Pangaea started to break up into two smaller supercontinents, called Laurasia
and Gondwanaland, during the Jurassic period. By the end of the Cretaceous
period, the continents were separating into land masses that look like our
modern-day continents.
 The theory of continental drift was not accepted for many years. One problem
was that a plausible driving force was missing. And it did not help that Wegener
was not a geologist.
 Other geologists also believed that the evidence that Wegener had provided was
not sufficient.
 It is now accepted that the plates carrying the continents do move across the
Earth's surface; ironically one of the chief outstanding questions is the one
Wegener failed to resolve: what is the nature of the forces propelling the plates?

12. Jigsaw Evidence
 Francis Bacon was one of the first people to note that the West
coast of Africa and Europe seem to have a “jigsaw fit” with the
Eastern seaboard of North and South America.
 Wegner provided more evidence stating that the shape of the east
coast of South America fits the west coast of Africa, like pieces in a
jigsaw puzzle.
 Alfred described how the continents would of fit together forming
a super continent which he named Pangea.
 However Wegener was trained as an astronomer and a
meteorologist therefore many geologists did not think that he had
the right background to judge or make geological theories. For
this reason they dismissed much of his evidence.

13. Fossil Evidence in Support of the Theory
 Eduard Suess was an Austrian geologist who first realized that there had
once been a land bridge connecting South America, Africa, India,
Australia, and Antarctica. He named this large land mass
Gondwanaland (named after a district in India where the fossil plant
Glossopteris was found).
 This was the southern supercontinent formed after Pangaea broke up
during the Jurassic period. Suess based his deductions on the fossil plant
Glossopteris, which is found throughout India, South America, southern
Africa, Australia, and Antarctica.
 Fossils of Mesosaurus (one of the first marine reptiles, even older than
the dinosaurs) were found in both South America and South Africa.
 These finds, plus the study of sedimentation and the fossil plant
Glossopteris in these southern continents led Alexander duToit, a South
African scientist, to bolster the idea of the past existence of a
supercontinent in the southern hemisphere, Eduard Suess's
Gondwanaland.
 This lent further support to A. Wegener's Continental Drift Theory

14. Ocean floor spreading theory
 In the 1960s a Scientist called Harry Hess said that not only were the continents
moving but also the sea floor was moving.
 The conveyer belt motion of the sea floor meant that youngest rocks were found on
the mid-ocean ridges and then get older, further away from the mid-ocean ridge.
This shows that the sea floor is spreading and ultimately moving the continents to
cause the continental drift.
 Hess said that the movement of the sea floor
was to do with the convection currents in the
mantle because the hot magma that rises is
less dense than the cooler magma; this magma
cools are forms new rocks when it reaches the
seas surface and consequently other magma
that rises pulls the sea floor apart moving the continents around. Then at the plate
boundaries the cool rocks sinks and melts from the mantles heat.

15. 2 new supercontinent
 South African geologist Alexander du Toit maps out a
northern super-continent, "Laurasia," to explain coal
deposits, which presumably indicate the remains of
equatorial plants, in the Northern Hemisphere.
 Laurasia formed when Pangea broke up to form 2 smaller
supercontinents.
 The other supercontinent was located
in the southern hemisphere and was
known as Gondwanaland.

16. Jack Oliver
 Jack Oliver provided a research
paper on plate tectonics that proved
vital in providing hard evidence for
the existence of continental drift,
which was released in 1968.
 The 1968 paper finally proved
Wegener right and continental drift
was accepted by the world of
science.