Transcript THE CONTINTENTAL DRIFT IDEA

THE
CONTINTENTAL
DRIFT IDEA
WEGENER’S THEORY
LESSON 2
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ALFRED WEGENER
 Alfred
Wegener was the
scientist who proposed the
Continental Drift Theory in the
early
twentieth
century.
Simply put, his hypothesis
proposed that the continents
had once been joined, and
over time had drifted apart.
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Before wegener …
 Before
Wegener developed his theory, it
was thought that mountains formed
because the Earth was cooling down,
and in doing so contracted. This was
believed to form wrinkles, or mountains, in
the Earth's crust. If the idea was correct,
however, mountains would be spread
evenly over the Earth's surface. We know
this is not the case.
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The continental drift…
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Pangea e Pantalassa
 Some
300 million years ago all the world's
land masses were beginning to form into
one
supercontinent,
Pangaea,
surrounded by a single universal sea,
Panthalassa.
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The theory of tectonics plate

Plate tectonics is a scientific theory that describes the
large-scale motion of Earth's lithosphere.

This theoretical model builds on the concept of
continental drift which was developed during the first
few decades of the 20th century.
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evidence for the theory:

1.
2.
3.
The geoscientific community accepted the theory
after this concepts:
the same types of fossilised animals and plants are
found in South America and Africa
the shape of the east coast of South America fits the
west coast of Africa, like pieces in a jigsaw puzzle
matching rock formations and mountain chains are
found in South America and Africa
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Accept the theory

In the 1950s, evidence from magnetism in the
ocean floor showed that the seafloors were
spreading by a few centimetres each year. This
showed movement of large parts of the Earth’s
crust, now called tectonic plates.
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There are three kinds of plate
tectonic boundaries:
1.
2.
3.
Divergent
Convergent
transform
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Divergent boundaries:

A divergent boundary occurs when two tectonic plates
move away from each other. Along these boundaries,
lava spews from long fissures ,frequent earthquakes
strike along the rift. Magma from the mantle solidifies
into basalt, a dark, dense rocks that underlies the ocean
floor.
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Convergent boundaries:

The impact of the two colliding plates buckles the edge
of one or both plates up into a rugged mountain range,
and sometimes bends the other down into a deep
seafloor trench. A chain of volcanoes often forms
parallel to the boundary, to the mountain range, and to
the trench. Powerful earthquakes shake a wide area on
both sides of the boundary.
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Transform boundaries:

Two plates sliding past each other forms a transform
plate boundary. Natural or human-made structures that
cross a transform boundary are offset—split into pieces
and carried in opposite directions. Rocks that line the
boundary are pulverized as the plates grind along,
creating a linear fault valley or undersea canyon.
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links
 https://www.youtube.com/watch?v=1-
HwPR_4mP4
 http://educationportal.com/academy/lesson/plateboundaries-convergent-divergent-andtransform-boundaries.html
 http://educationportal.com/academy/lesson/alfredwegeners-theory-of-continental-drift.html