9.39 Outer Core Facts

Earth is divided into three main parts: the crust, the mantle, and the core. But did you know that the core is actually made of two different layers? In this lesson, we will talk about the outer core of Earth.

Earth’s Layers

What happens if you mix oil and water together? The oil stays on top of the water because oil is less dense than water. Density refers to how much space something takes up and how heavy it is. The more space something takes up and the heavier it is, the denser the material will be. If you have never seen this, try it now with some water and cooking oil!

The earth beneath our feet is made up of layers. Like the oil and water, Earth’s layers are divided by how dense they are.

The water goes to the bottom of the cup because it is denser than the oil. This experiment illustrates how the core got to be in the center of Earth, because the core is the densest layer.
| |

Earth is made up of several layers. At the surface of the earth, or the part we walk on, is the least dense layer. Each layer below the surface becomes denser and denser. The core is the layer at the center of the earth, and it is made of materials that make it the densest layer. You may have heard all of this stuff already, but did you know that the core is actually two layers? Let’s take a look at one of these layers, the outer core.

The Layers of the Earth
| |

1. Main points:

The concept of density explains why oil floats on water and also illustrates how Earth’s layers are arranged, with the densest layer, the core, at the center. Earth’s core is composed of two layers, with the outer core being one of them.

2. Questions:

• Content Analysis: What does the experiment with oil and water demonstrate about density?
• Thematic Analysis: How does the concept of density relate to the structure of the Earth?
• Socio-cultural Analysis: Why is understanding Earth’s core important in studying the planet?

3. Further Discussion:

• If you could explore any layer of the Earth, which one would you choose and why?

4. Answers:

• Content Analysis: "The oil stays on top of the water because oil is less dense than water. Density refers to how much space something takes up and how heavy it is."
• Thematic Analysis: "Like the oil and water, Earth’s layers are divided by how dense they are… The core is the densest layer."
• Socio-cultural Analysis: "The core is the layer at the center of the earth, and it is made of materials that make it the densest layer."

About the Outer Core

The core is made mostly of two metals called iron and nickel. The outer core is the outer layer of the core that is made of liquid iron and nickel. Since it is a liquid, the outer core can spin, and it does. This spinning causes the entire planet to be magnetic (think of a refrigerator magnet). The magnetism of Earth actually helps us a lot, because it stops some harmful materials from hitting our planet.

How is the Outer Core Different from the Inner Core?

Although they are made of the same materials (iron and nickel), the inner core and outer core are different in one very important way. The inner core is solid, and the outer core is liquid. The inner core is solid because the pressure is so much higher in the very center of Earth. The higher pressure makes it solid even though the temperatures of the inner core and outer core are basically the same.

How Do We Know About the Outer Core?

This image shows the spinning core.
| |

Obviously, we can’t drill down to the core to study it. It is way too hot, and our machines would melt way before we hit the core. Instead, scientists study earthquake waves so they can understand what is happening beneath our feet. The way earthquake waves bounce off the core helps us understand Earth’s layers.

1. Main points:

The Earth’s outer core, composed of liquid iron and nickel, spins and generates the planet’s magnetism. It differs from the solid inner core, which remains solid due to intense pressure. Scientists study the Earth’s core indirectly through the behavior of earthquake waves.

2. Questions:

• Content Analysis: What is the composition of the outer core and how does it contribute to Earth’s magnetism?
• Thematic Analysis: How are the inner and outer cores different in terms of their physical states?
• Socio-cultural Analysis: Why is studying earthquake waves crucial for understanding the Earth’s core?

3. Further Discussion:

• What do you think would happen if Earth didn’t have its magnetic field?

4. Answers:

• Content Analysis: "The outer core is the outer layer of the core that is made of liquid iron and nickel… This spinning causes the entire planet to be magnetic."
• Thematic Analysis: "The inner core is solid, and the outer core is liquid. The inner core is solid because the pressure is so much higher in the very center of Earth."
• Socio-cultural Analysis: "Scientists study earthquake waves so they can understand what is happening beneath our feet. The way earthquake waves bounce off the core helps us understand Earth’s layers."

Lesson Summary

Earth is divided into three main layers. The core is the densest layer and is at the center of Earth. It is divided even further into two layers: the outer core and the inner core. The outer core is made of liquid iron and nickel and is constantly spinning.