Section 1 is about the interior of the Earth, what the inside of Earth is like, and how geologists know what is inside the Earth.
Geologists have 2 ways to figure out what makes up the interior of the Earth. First, they have an indirect way of doing it. The scientists collect rock samples from inside the earth. Second, they use an indirect way. They track seismic waves during an earthquake to see what is inside. We cannot dig a hole through the earth to find out what’s inside because of the extreme heat and pressure that increases the further you go inside.
Using seismic waves and rock samples, they’ve discovered that the earth has 3 main layers, each composed of different materials, different sizes, and have different temperatures. There is a crust, a mantle, and a core, which is divided into an outer core and an inner core. The crust is the thinnest layer of the earth. There are 2 parts of the crust: a thicker continental crust under continents, and a thinner oceanic crust underneath the oceans.
Below the crust is the mantle. The upper part of the mantle is called the lithosphere. Under the lithosphere is the asthenosphere, which is soft but solid rock. Underneath the asthenosphere is the lower mantle. The whole mantle is made of hot but solid rock.
Under the mantle is the outer and inner core. The outer core is liquid. It’s mostly made of iron and nickel. The very center of the earth is the inner core. It is solid iron and nickel because the pressure of the other layers squeezes it. The core is the hottest part of earth. It is about 4000 degrees Celsius!