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Convection Currents- These movements occur in the mantle. Hot magma is heated by being on the bottom of the mantle, near the outer core. This heat rises and shoots up to the top of the mantle. It cools, and falls back to the bottom of the mantle. This constant movement in the mantle cracked the Earth’s plates and caused the continents, the rock and even the oceans to almost float above the mantle. As the hot magma shoots upward, as it comes out through the valley of the Mid Atlantic Ridge, the two plates are pushed farther and farther apart
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Plate Tectonics- This is a theory that the Earth’s Crust cracked and we call the pieces or cracks, Plates. There is a lot of evidence that this occurred. First is the fact that the ocean floor seems to be getting bigger, while the continents seem to be moving farther and farther apart. Since we have already learned that the entire Earth’s crust is rock and the next layer down is the mantle, which is made up of molten magma, it does seem possible that the rock crust can move and shift over the molten magma.
Sea Floor Spreading- It seems that the cracks in the ocean floor have let magma come up and fill in, pushing the sea floor apart, making the continents move farther and farther away from each other. major types of fossils
Imprint- when an organism lies down on wet sediment and somehow the imprint of the organism remains after the organism is gone, like a foot print in cement Permineralized- when sediment fills the organisms soft and empty parts and other sediment completely covers the organism. In this case the sediment takes on the shape of the organism, long after the organism has decayed Amber- when an organism is covered in Sap and the sap hardens into amber, the organism remains like a mummy inside of the amber stone…. This is useful for scientists because they can study the organisms DNA The relative age of a fossil is a comparison of all of the fossils found on a particular area. Those fossils found closer to the bottom beds of sediment are older. Those fossils found near the top are younger. We can not necessarily find out how old a fossil is with this process, but by comparing the areas the fossils are found, we can determine which is older and about how much older Absolute age has to do with a fossils real age. Scientists are able to do this by using chemicals and testing to find out the actual age of the fossil. They do this by radioactive decay and looking at the half lives of the parts they break down. The fossil record is an incomplete record of all fossils found. It is incomplete because, not all extinct creatures left fossils. |
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