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Lecture 7

EPSC201 Lecture 7 Notes.doc


Department
Earth & Planetary Sciences
Course Code
EPSC 201
Professor
Anthony Williams- Jones
Lecture
7

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EPSC201 - Lecture 7 Notes
Continen- tal Drift:
The conti- nents fit together like puzzle pieces, which suggests the
continents used to be connected. Alfred Wegner, a meteorologist and
glaciologist from Swisszterland, found signs of glaciations in places
where there shouldn’t be. He fit the continents together,
and called the massive one continent Pangaea. He con-
cluded that the continents must have slowly drifted to-
gether.
Key
line
of evi-
dence – places where there shouldn’t be glacia-
tions have signs of it. Glaciers tend to polish and
erode the rock. They have a scraping and
scratching effect. Glacial striation along the side
of mountains can indicate flow of glacier.
When plaining wood, one direction is very
smooth and the opposite direction is very rough.
The exact same phenomenon is observed with
glaciations striations. From this you can extrapo-
late what direction the glacier was flowing.
Glaciers scrape huge grooves in the land, which
form lakes. These lakes will be all scraped in the same direction.
Wegner noticed this glaciations all over the
world, like South Australia and South Africa.
These signs were millions of years old. He
measured the directions, and noticed they all seemed to be moving
radially and Northward. Wegners arguments were that the
areas that were glaciated must have been located
near the South pole. They must have migrated
Northward over time.
Gondwanaland – the Southern continent pic-
tured by Wegner. This was Wegner’s key piece
of in- formation the supported the theory of continental
drift
Laurasia – the Northern continent pictured by Wegner, much trickier then Gondwanaland
Pangaea – the combination of Laurasia and Gondwanaland.
When Wegner presented his idea in the 1920s, people laughed at him, because he couldn’t explain HOW
the continents drifted.

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In North America, the idea of continental drift
was rejected until the 1960s. In the southern hemi-
sphere, the idea was more readily accepted.
Huge forests make coal deposits. If you map the coal
deposits, you can map the roughly equatorial zone. If
you put all the continents together, they roughly make a
line. If you move all the continents to current locations,
the coal locations are all over the place. Suggests that
the continents use to be together and the equatorial
area had lots of forests, which eventually turned to coal.
Deserts and areas close to the coast are where salt de-
posits form. This map shows that the continents used to
be together, and the deposits of coal, salt and deserts,
would have all be in similar locations.
Shown be-
low is Gondwanaland, and shows how fossil records show
the continents used to be together. The animals shown below
only move around on land, yet the exact same species fossils are
found all over the world.
Key point – Land restricted species found on different conti-
nents.
Lystrosaurus fossils are even found on Antarctica, so
clearly Antarctica must have been warmer in the past,
then now. Ferns are also found on both Antarctica and
Australia, which suggests that these
continents were connected and in a warmer loca-
tion.
It is also possible to look at geology. If the same
composition is found on two continents, it is possi-
ble to show that they were connected.
For example, the West Coast of Africa has the ex-
act same composition as the East of the Americas.
This shows the two mountain belts on these conti-
nents were connected, and have drifted apart over
time.
Before Pangaea, there were other super continents. We will discuss
this later on.
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