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Transcript
Crust The Earth consists of four main parts, the inner core, outer core, mantle and the crust. The crust is Earth’s most external layer out of all the four layers mentioned. The crust consists of two parts the oceanic and continental crust. These crusts hover above the earth’s mantle, which is basically a river of molten rocks that is 2850 km thick. This outer most “coating” is more emaciated when compared to the other layers. If you were to look at the whole world through a satellite screening you would be able to tell that the majority of the earth is covered by a great deal of water. Below these large masses lies one of the two types of crust, the oceanic crust. This crust is approximately 4-7 miles thick. When compared to the continental crust, this crust is much younger. The oceanic crust has its own type of rocks, known as tholeiitic basalt. Theoliitic basalt has a very dark, gritty, and fine volcanic structure formed from much liquefied lava. The grains of this rock are so small you must operate a microscope to be able to have a clear observation of the material. This crust on average has a density of 3g/cm3 We by now know that the earth is mostly covered with oceanic crust; the other small percent is land. “Land” as we refer to it was actually a gargantuan ground mass way back, known as Pangaea. As the years passed on, movements of the earths crust began to break down the “super continent”, which eventually led to the creation of 6 large masses of land other wise known as continents. These continents are part of the continental crust. The six continents are Eurasia, Africa, North America, South America, Antarctica, and Australia. Scientist hasn’t really identified the thickness of this crust but they say on hypothesis that below the continents is approximately 26-40 miles max. This crust is much older than the oceanic crust, mentioned above reaching to ages of about 8 billion years old. The continental crust consist of two layers the upper and lower magma. Both layers produce rather igneous rocks, the upper produces granite. Granite has light coloration and is a coarse grain of magma. The lower part produces diorite, which share same compositional make ups with granite, but is scarcer, which is formed by impurities within the magma. On average the density of the continental crust is 7g/cm3 The crust itself does not affect or influence the earth however; the movements of these do leave a mark. The movements of plates are caused by convection currents. These measurable movements cause minor or dramatic earthquakes, which delivers regrettable results. Some times at the weak points volcanoes have the capability of erupting. Due to all these movements of the earth’s crust we now have valleys and mountains.