Tectonics

The earth, from its deep majestic oceans to its breathtaking mountains, is our home. But what goes undetected to humans is the violent cycle that is going on underneath our earth at this very moment. Volcanoes are spouting hot magma. Earthquakes are destroying cities and the continents we live on are moving around the ocean. But why do these phenomenon occur and what causes them to happen?

From space the earth may look like one large floating mass. But underneath all of the oceans and continents there lies many large. These plates were once all formed together in one large continent called Pangaea. Over the millions of centuries the plates have shifted and formed the continents that we now see today. Scientists first discovered this theory when they noticed that the Northeastern part of South America seemed to fit into the Southwestern part of Africa. These plates have been very instrumental in the forming of our planet. They form the high mountains and the deep oceans. They form volcanoes and cause earthquakes. The plates underneath our earth are very important to us and I believe we need to pay more attention to them.

The plates themselves are very large, the largest being the Pacific and Antarctic plates. There are two types of plates on the earth. The first, oceanic is made up of a heavy rock called basalt. This causes the plate to sink deeper into the earth’s mantle causing our oceans to appear. The other type of plate is continental. These plates are made up of granite, which is much lighter than the basalt that makes up the oceanic plates. Oceanic plates are not as thick as continental plates. Oceanic plates average 5 kilometers in thickness while continental plates can be up to 100 kilometers thick. This allows the formations of mountains to occur.

The plates were first outlined by charting where the major earthquakes were occurring and drawing a line, more or less down the center of them to show a line of best fit. This was first done in 1961 and it outlined the main plates of the world.

500 million years ago the earth was not made up of the seven continents we see today. It was made up of one giant continent called Pangaea(see figure C). Around 200 million years ago the continent Pangaea broke into smaller continents called Gondwanaland and Laurasia. Over time these two continents slowly broke apart to form the continents we see today the reason we see the continents as they are today is because of continental drift. Scientists believe that this may not be the only time there has been a “Pangaea”. Continental drift has caused the separation of many of the “Pangaea’s” in the past before the one that existed 200 million years ago. In 250 million years scientists believe once again that the continents will come together forming what they call “Pangaea Ultima” and eventually Pangaea Ultima will once again break apart forming new continents.

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Engr.Aftab