Mountains Near The Edges Of The Plates example essay topic

The Shifting of Pangea Have you ever noticed that a map of the world looks like a puzzle and the continents look like the pieces that would fit together to complete the puzzle. In 1912, Alfred Wegener, a German scientist and an adventurer, came up with a theory that the continents had once been part of a "supercontinent". Wegener proposed that, over 200 million years, what he called Pangea had separated and became individual pieces. Pangea means "all lands" in Greek, and that is what Pangea was, a very large landmass when all of the continents were connected. When Wegener first proposed this idea in 1912, people did not buy into this theory. One of the problems that Wegener faced was that he believed that the continents had drifted apart, but he couldn't explain how they had drifted apart.

Another problem was that there was a theory already in place called the "Contraction Theory". This theory stated that the Earth was once a molten ball and in the process of cooling, the surface cracked and folded up on itself. One of the problems with this theory was that it suggests that all mountain ranges were the same age, and this could not be true. Wegner's explanation was that continents shifted and these shifting plates would collide, encounter resistance from one another, compress, then fold upwards to form mountains near the edges of the plates. Eons ago India and an ancient ocean called the Tethys Ocean sat on a tectonic plate. This place was shifting northward towards Asia at a rate of 10 centimeters per year.

The ocean got progressively smaller unit about 55 million years ago when it collided with Asia. There was no more ocean left of lubricate the subduction and so the plates formed the High Plateau of Tibet and the Himalayan Mountains. Evidence that Pangea may have existed can be found in land animals, vegetation, mountains, and the climate. Fossils and plants that are the same, can be found on different continents, across oceans.

Assuming that the land was once connected, animals could have walked across the large land mass and not have to swim. For example, the mesosauras (a land animal) could not have traveled from South America to Africa because of the Atlantic Ocean. Yet, there are fossils of this animal on both continents. Another example is there are trees in South America, Africa, India, Australia, and Antarctica that are of the same origin.

How would the seeds have traveled over so many different continents? One explanation is that the lands were once connected. Other evidence is the formation of mountains. The Appalachian Mountains are found in North America as well as the British Isle and Scandinavia, which is now separated by the Atlantic Ocean. The mountains are of the same age and structure. More evidence why scientists believe in the Pangea hypothesis is the climate.

Since the Southern Hemisphere was once by Antarctica and the Northern Hemisphere was once by the equator, the climates were different than those we know today. There is evidence that ice sheets once existed in the Northern Hemisphere. The temperature of the earth hasn't changed much, but the location of the continents have. The earth's core is made up of nickel and iron ball encompassed by an outer shell of molten metal. After that is a space of rock call the mantle. In the first part of the earth's existence, an outer layer of hot rock cooled to make the earth's surface, or the lithosphere.

The top layer, which is the most brittle, of the lithosphere is called the crust. Over millions of years the earth's crust has cracked making huge stone slabs called plates. There are seven large and dozen smaller plates. The plates seem to float on the mantle and move around when the plates around them cool and move. The places where these plates come in contact with one another are called faults, or fault lines. At these places of impact, there is much seismic and volcanic activity.

At the location were plates collide against each other the plates can at in three different ways: they can push against each other and form mountains; they can "slide" past each other sometimes starting earthquakes; or one can dive beneath the other, when this happens the descending plate can melt and rise up and form a volcano. The plates are still moving, and the Atlantic Ocean will be much larger in 50 million years and the Pacific Ocean will be smaller. North and South America will have moved farther west, while Greenland will have moved farther northwest, the western part of Africa will rotate clockwise and run into Europe. Also, Australia will move farther north into the tropics, while New Zealand will move to the south of Australia. These are just predictions and these movements of the continents may only happen is the plates continue to move in the direction that they are currently moving, and at the same rate of speed.