Geological Time Periods | Search The Web!
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| The Earth has not always been like it is now, especially not in its geography. Our Earth was formed when large masses of dust and gas settled together over millions of years, to form a planetoid. This small, lifeless mass would someday be earth. The tiny planet was continually rained down on by tons of meteors, adding to its mass and gravity. The higher its gravity was, the more meteors were drawn to it, so the larger it became. All this friction generated large ammounts of heat, making the Earth hot all over, like the mantel with the crust ripped off. |
| Eventually, the sun grew and heated up, and sent off a huge nuclear wind, which blew all the stray asteroids into a belt between Mars and Jupiter, away from the Earth. Now the Earth's crust could cool. Back then, the Earth wasn't a nice place. It was very hot, because it did not yet have an atmosphere, and was very dim, because our sun was just young. Volcanoes erupted everywhere as the Earth's crust settled. |
| Eventually, it cooled off enough and formed the solid crust we have today. The volcanoes and created large ammounts of steam, so, when it was cool enough, it rained. Boy! did it ever rain a lot. It did nothing but rain for millions of years, and covered most of the Earth with a vast ocean. After 4 billion years of its existence, Earth could support life, and it did. The appearance of life marks the end of Pre-Cambrian times. 400 million years later, the atmosphere and ozone were formed, and life could come up on land. |
| In Cambrian times, most of the Earth was covered with a shallow sea. Eventually, all of the continents joined together in one giant supercontinent called Pangaea (I have a rabbit named Pangaea. She is nice and spotted). It was Alfred Wegener who first came up with the theory of a supercontinent, because all the shorelines of the continents seem to fit together. He also came up with the theory of continental drift. The theory is basicly this: The Earth's crust is made up of about 20 plates. These plates all sit on the mantel of the Earth, which is a large layer of molten rock. It has the consistency of plastic. The movement of the plates is caused by convection. The core of the Earth is really hot. The heat generated from in there rises, as heat tends to do. But when it reaches the top, it cools down, and drops again. This creates currents beneath the Earths crust, which are responsible for the movement of the plates and continents. |
| Back then, when all the continents were joined into Pangaea, there were no polar regions, and the climate over the whole Earth was warm and wet. Dinosaurs could roam over the whole world and not have to worry about getting stopped by the sea. |
| Then, in the Triassic Period, Pangaea began to break apart into the continents we have today. They very slowly were all drifting away from each other. We now have measurements to prove that the continents are still slowly drifting away from each other today as we speak, at a rate of up to 1 inch a year. Eventually, North America will collide with Asia. |
| During the Cenozoic Era, the North American Plate had drifted far north. Ice sheets advanced downward, then receded, about every 10,000 years. There were four major periods of ice coverage. This time came to be known as the ice age. The climate was also changing rapidly as the continents drifted, getting closer and closer to how it is today. In the Miocene Epoch, many mountain formations were formed, like the Alps, Andes, and Himalayas. About 50,000 years ago, the Pleistocene epoch ended and humans evolved, to change the land forever with our cities. |