Azuhura Msofe
Humanities-8B
17/September/09
Miss Nickell
Plate Tectonic Unit
4,600,000,000 years ago the seven continents of today were once one
“supercontinent” called Pangaea. This theory was developed by a man named Alfred
Wegener in 1915. Even though Alfred Wegener’s’ theory was considered unrealistic and
that there was no way possible the Earth mass could have once been one, evidence
started showing up to prove Alfred’s theory and people started rethinking his theory.
Some of the evidence that was discovered to prove Alfred’s theory was that the same
animal fossils were found in different countries as well as plants. Exactly the same rocks
were exposed then discovered to be in more than one country. Lastly the sea floor is
spreading and it is believed to have spread the coasts of countries apart or together.
One example to prove Alfred Wegener’s theory of Pangaea is that fossils of the
same species of animals were found in different countries that are separated by land
masses of water now days. As well the same plant fossils were found in different
countries. Glossopteris fossils (a fern tree) were found in South Australia near
Melbourne, the North coast of Antarctica near Prince Herald, Southern India and
Southern Madagascar.
This is a picture of a
Glossopteris fossil.
<http://www.rosssea.info/pix/big/Gl
ossopteris.jpg>
Also fossils of Cynognathus a land reptile were discovered in Argentina and South
Africa. Mesosaurus a fresh water reptile have been found in Eastern Brazil and
Cameroon. If we look at this logical it means that the continents of Africa and South
America had to be connected and Alfred figured this out.
Another type of land reptile called a Lystrosaurus was found
in Antarctica, Madagascar north of Antananarivo, Central
India and Eastern Tanzania near Dar Es Salaam.
This picture shows that South America and Africa
were once one like Alfred said. The evidence to prove it is that
the coast lines fit together perfectly. This would explain why Cynognathus and
Mesosaurus were both found in Africa and South America.
<http://members.fortunecity.com/geology99/paloma/fit.gif>
This is a picture to show
what I was saying in my
first paragraph. That all
the Southern Continents
called that were called
Gondwanaland were all
connected. South
America and Africa had
fossils of a Cynognathus.
South America, Africa,
Madagascar, India,
Antarctica and Australia
all had fossils of Glossopteris and Africa, Madagascar, India and Antarctica all had fossils of
Lystrosaurus. Mesosaurus a fresh water reptile have been found in Eastern Brazil and
Cameroon.
<http://www.emc.maricopa.edu/faculty/farabee/BIOBK/aFig4.gif>
In addition, the exactly same rocks were found in different parts of the Earth’s land
masses. One type of rock that was found is called igneous rock or can sometimes be
called “fire rocks” that can be formed underground or above land by molten rock which
magma (underground) or lava (which is above land) that erupts out of volcano’s. Under
the Earth the magma of a volcano starts shooting up looking for any small hole to burst
through but while it is shooting up some of the magma gets trapped in small caves like
holes and starts to cool. As it cools it hardens and turns into what we call igneous rock.
Above land the same magma that was shooting up finds a hole it can burst through,
once out it is too hot to cool so it moves down the hole slowly and after a while when the
erupting as stopped the lava starts to cool down. As the lava cools it hardens and forms
igneous rock. (“How Igneous Rocks Are Formed.”)
This is a picture Arenal
Volcano erupting in
Costa Rica.
This is lava because it
is above land and it is
slowly moving down.
<http://en.wikipedia.org/wiki/File:Arenallong.jpg>
This is igneous rock.
The lava has cooled
down and
transformed.
<http://en.wikipedia.org/wiki/File:Ropy_pahoehoe.jpg>
The second type of rock is sedimentary which is formed from small piece of eroded
Earth been compressed so much that they form rocks. For example limestone is a
sedimentary rock because it is made up of calcium carbonate (CaCO3) from evaporated
lakes or seas. The powder has been compressed so much that it transformed into a
rock. Both these types of rocks have been found in South America and West Africa
furthermore supporting Alfred’s theory. (“How
Sedimentary Rock Is Formed.”)
The rocks the arrow is
coming from are
limestone’s growing
̃̃̃̃
on the beach of Sã̃̃̃̃̃̃̃o
Pedro de Moel.
<http://upload.wikimedia.org/wikipedia/commons/3/31/Limestone_cropping.jpg>
Finally, the sea floor is spreading and pushing the continents apart. We have
enough evidence to prove that there was once a “supercontinent” but what stops some
people from believing that there was once Pangaea is the fact that all the continents are
so far apart but that can be explain. The sea floor plates are spreading apart from each
other allowing magma or sometimes know has lava to rise up and create a new floor.
Now since the sea floor plates are spreading it is pushing the continents away from
each other. This action has been going on for millions and millions of years and it has
pushed the countries to where they are now. (Ritter, Michael. “Sea-Floor Spreading.”)
This is a picture of the sea floor
spreading. It shows the magma
rising up, the ocean crust or ocean
floor moving a part from each
other and the continents forced to
move a part.
<http://www.physicalgeography.net/fundamentals/images/seafloor_spreading.gif>
To conclude even though Alfred Wegener’s theories were not accepted back
then, we thank him for recording them because if he hadn’t his future generation which
are us wouldn’t have known. We wouldn’t have known that with one step you could be
in South America and then take another step and you could be back in Africa. Or that
Antarctica wasn’t always a cold place it was once hot because coal has been
discovered there and coal can only be found in hot places.
Bibliography
1. Name N/A. “How Igneous Rocks Are Formed.” Modified on 9/22/2009. Rock
Hounds. Accessed 22/Sept/09.
<http://sln.fi.edu/fellows/payton/rocks/create/igneous.htm>
2. “Plate Tectonics: The Main Features Are.” Modified on 9/22/2009. Earth Science
From Moorland School. Accessed on 22/Sept/09.
<http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html >
3. “How Sedimentary Rock Is Formed.” Modified on 9/22/2009. Rock Hounds.
Accessed on 22/Sept/09.<http://fi.edu/fellows/fellow1/oct98/create/sediment.htm
>
4. Ritter, Michael. “Sea-Floor Spreading.” Modified on September 26, 2006. The
Physical Environment. Accessed on 22/Sept/09.
<http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html>