Alfred Wegener & Continental drift

1. Alfred Wegener’s Theory
and Evidence
By Tiara, Evelyn and Katelen

3. Wegener’s Theory
A revolutionary theory by Alfred Wegener, a
german meteorologist and geophysicist
changed the world’s perspective of the Earth.
This theory was proposed between 1912 and
1915. His theory was that the continents were
once joined together and gradually moved apart
over millions of years. It offered an explanation
for the existence of similar fossils and rocks on
continents. However, this theory took a long
time to be accepted, due to the lack of
evidence.
Pangaea

5. From Pangaea to Gondwana and
Laurasia
Pangaea was the supercontinent that included almost all of Earth’s landmasses
and spread across nearly ⅓ of Earth’s surface. The global ocean that
surrounded it was called Panthalassa ocean. Pangaea became fully assembled
around 270 million years ago and then around 200 million years ago, it began
to split apart.
It was then theorised that the supercontinent divided into two land masses
called Gondwana and Laurasia. The division occurred approximately 200
million years ago.
Gondwana was the Southern Landmass and consisted of the current
continents: Australia, Africa, South America, New Zealand, Madagascar, India
and Antarctica.
Laurasia was the Northern Landmass and it consisted of the current continents:
North America, Europe and Asia.

6. Continental Drift
- Geological theory states that the positions of the continents on Earth have moved to
different positions over time. This movement was called ‘Continental Drift’.
Continental Drift is a result of large convection currents in the earth’s mantle. There
is now, much evidence to support this theory of the continents moving. Similar plant
and animal fossils can be found on the shores of various continents, further implying
that they were all once joined. For example: a crocodile fossil was found in both
Brazil & South Africa, another reptile’s fossils were found in South America, Africa
and Antarctica. In addition, there is also some living evidence—species of some
earthworm families found on South America and Africa. Therefore the theory was
proved by three main pieces of evidence :
- Landforms
- Fossils
- Climate

7. Evidence Alfred Wegener single-handedly demolished the theory that large land
bridges once connected the continents that had sunk into the sea as
part of a general cooling and contraction of the Earth. He proved that
the continents are made of various, lesser dense rock than the volcanic
basalt that makes up the deep-sea floor in which Wegener proposed
that the continents floated like icebergs in water.
He discovered that land bridges once connected the continents and
that they have since sunk to the ocean bottom as a part of a general
cooling and contraction of the Earth.
Continents that are made up of less dense rock (granite) rather than the
volcanic basalt that makes up the deep-sea floor. Wegener proposed
that continents floated in the ocean like icebergs.
If continent sized land bridges had once existed and had somehow
been forced to the ocean bottom, they would have “bobbled up” again
when force was released.

8. Thankyou