Essay Lesson 15 : Earth’s interior

The earth’s  crust, mantle, and core 

The earth’s crust is divided into two crusts one being the continental crust and the other being the oceanic crust.The primary rock found on the earth’s crust is the granite and igneous rock.The continental crust is 18.6-31 miles miles thick, and it is primarily composed of felsic rock.Then there is oceanic crust which is 4.3 miles thick and is primarily composed of mafic rock.Mafic rock contains magnesium and iron.even though the oceanic crust is thinner it is more dense.No machine has ever been able to drill a hole through the earth crust.

The earth’s mantle is mostly solid there are areas in the mantle that has semi melted rock also none as magma chambers and the upper mantle possible consists of ultramafic rock which is  very dense igneous rock the crust and the upper mantle are the lithosphere which is the earth’s plates that move on the earths the lower layer  under the lithosphere is the asthenosphere scientists believe this is a slushy area some of the rock is crystals and the others are liquid  

The earth’s core seismic waves do not appear on the other side of the earth the shadow zone. S waves are the epicenter of an earthquake .Seismologists know that the S waves don’t go through the center of the earth so there is a shadow zone where the seismologist don’t see the occurrence of the s waves. P waves go in other directions like S waves but they start going through the core then start refracting and bending and then start to bend. Even though there are still shadow zones . It is a scientific fact that the core is more dense and is metal.

Earth’s  magnetic shield

The north pole is magnetic south and magnetic north is the south pole. The reason a magnet needle points to the north pole/magnetic south is because the earth is a giant magnet. With magnets opposites attract but if you put both north sides together they will repeal the reason is because the magnetic force that is generated is going the same direction so they are repelled. A compass has a lightweight magnet inside that points to the earths north pole.The magnet picks up the earth’s magnetic field . The earth’s tilt is 11.5 degrees because North is actually 11.5 degrees from south  

Earth’s floor

Evidence suggests that the earth’s plates have moved a lot since the begging of time. These earth plates move from 0.5 to 6in per year. There are ocean floor ridges that indicate that on both sides of the earth’s floor are moving. As the seafloor is expanding there are magma chambers that create more rocks once it cools but it shrinks along the seafloor then it goes under the continental plate and creates mountains. The plate goes down and starts to melt and it goes through the mantle and starts all over again 


An earthquake is a movement alongside boundaries or faults. A fault is a break between rocks. An earthquake is a sudden occurrence of released energy that has been stored. Earthquakes normally occur deep inside the earth sometimes 435 miles deep mostly near the crust. There are three different faults the first is a strike slip fault 2 rocks grind past each other . The second is a normal fault where 1 rock slides down into the ocean ridge. The third is reverse fault where two rock collide into each other.

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