The main idea that I would like you to get from this set of notes is that convection currents are a swirling motion of a fluid that needs a heat source and a cold source to work. The rest of the notes will deal with supporting this idea and giving some examples of convections currents here on earth.
Once the earth collects enough material it will start to get so heavy that it compresses inward toward the center of gravity a lot. This smashing of the atoms of rock causes them to get really hot. Radioactive atoms are also giving of energy. The combination of the two heat sources made the earth so hot that it turned into a molten ball of rock. The fact that everything turned into a liquid allowed the heaviest material to sink to the center of the earth. This forces lighter material out of the way, eventually placing it on the outside edge of the earth and heaviest material on the inside of the earth. The fact that these layers have been created is actually what allows convection currents to form in the first place.
The layers cause specific material, radioactive material, to be concentrated in the center of the earth. This is important because a concentrated heat source is needed to get convection currents to work. If the heat were spread out all over the place, there would be no place for the heated magma to go. When the core gives off the heat energy from radioactive decay and compression, it excites the electrons of the magma nearby. The atoms of magma will push away from each other as the electrons jump to new energy levels. This makes the magma near the core much more spread out and lighter than the rest of the magma around it. Gravity pulls on the denser magma harder than the lighter magma. So the denser goes down towards the core and forces the lighter magma out of the way so that it goes up towards the surface of the earth. However, if the earth were not layered there wouldn't be a...
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