CLASS SET: DO NOT WRITE ON
Answer on your OWN sheet of paper
The Earth’s Layers
Human beings have always imagined what it would be like to journey to the center of the Earth. There are
many books and movies about characters who have adventures that take them to the Earth’s core, or even all the
way to the other side of world! It’s fun to pretend that we can tunnel to China, but scientists have proven that
humans will never be able to dig through the center of the Earth. The Earth has three very thick layers, and the
center is so hot that humans could never survive there. In this lesson, you will learn about these layers from the
inside out.
The Core
The core is the innermost layer of the Earth. It is made up of two parts: the inner core and the outer core. At the
very center of the Earth is the inner core. It is solid, and is made up almost entirely of iron. The inner core remains
solid because it is under an extreme amount of pressure. It is about 1200 kilometers thick.
Have you ever heard that the Earth’s center is made up of lava? While that is not technically true, the core is
partially liquid. This liquid layer is called the outer core because it surrounds the inner core. It is made up of iron
and another metal called nickel. It also contains sulfur. The outer core is kept very hot by the Earth’s inner core.
When elements like metal get very hot they become molten, or liquid. The outer core is about 2300 kilometers
thick.
The Mantle
The middle layer of Earth is called the mantle. At 2900 kilometers deep, it is the thickest layer of the Earth. Like the
core, the mantle has two layers, the upper (asthenosphere) and lower (mesosphere) mantle. Because of its
thickness, the mantle is where most of the Earth’s heat is located. The average temperature of the Earth’s mantle is
about 1000 degrees Celsius. At this temperature, the mantle remains a solid, but is flexible like plastic. When a
heavy load like an ice cap pushes on the mantle, it can flex and move out of the way to make room. Once the load
lessens, the mantle can return to its original position.
The mantle retains a lot of heat, which is circulated throughout the mantle in spaces called convective cells. The
movement of heat can cause the plates of the sea floor and continents to shift. Over millions of years the plates of
the earth can move quite a lot. When these shifts happen quickly, we experience earthquakes.
The Crust
The top layer of the Earth is called the crust. The crust is the layer upon which we live and build our cities. The crust
is the layer that can sustain life, yet it is the thinnest layer of the Earth. If you measure the thickness of the Earth’s
mantle on a continent, it would be between 35 and 55 kilometers thick. If measured from the deepest basins of the
ocean, the mantle is only 5 to 10 kilometers thick. It is made up of brittle minerals like calcium and sodium.
Because it is very cold compared to the mantle and core, the crust is easily cracked and broken. However, the crust
is also where we find valuable resources like oil, water, and gas.
Summing Up
With special instruments, scientists have been able to create detailed maps of the Earth’s layers. By measuring
temperature, sound waves, and other factors, earth scientists are able to find fossil fuels, element deposits, and
even underground lakes! New technologies even allow scientists to study the changes deep in Earth’s core. We
may never be able to journey to the center of the Earth, but each day scientists make discoveries that help us
understand more about the planet upon which we live.
Copyright 2009 LessonSnips www.lessonsnips.com
CLASS SET: DO NOT WRITE ON
Answer on your OWN sheet of paper
The Earth’s Layers Questions
1. Which one of the following is not one of the Earth’s layers?
a. Inner core
b. Crust
c. Outer mantle
d. Lower mantle
2. Starting with the outermost layer, what is the order of the Earth’s layers?
a. Core, mantle, crust
b. Crust, mantle, inner core, outer core
c. Mantle, outer crust, inner crust, core
d. Crust, asthenosphere, mesosphere, outer core, inner core
3. The core of the Earth is made up almost completey of which element?
a. Granite
b. Sulfur
c. Iron
d. Calcium
4. Which layer of the Earth is the thickest?
6
a. Mantle
b. Inner Core
c. Outer Core
d. Trick question- each of these are the
7
same thickness
5. Which of the Earth’s layers is liquid?
a. Lower crust
b. Asthenosphere (upper mantle)
c. Mesosphere (lower mantle)
d. Outer core
8
6. - 14 Label the diagram with the
following:
Lithosphere, Mantle, Outer Core, Crust,
Asthenosphere, Oceanic Crust
9
Continental Crust, Inner Core, Mesosphere
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
10 Type
11 Type
12
13
14
TRUE/ FALSE
The outer core is liquid.
The center of the Earth is made of molten rock.
Most of the Earth’s heat is stored in the mantle.
Earthquakes occur when heat travels through the mantle and causes tectonic plates to shift.
The thinnest parts of the Earth’s crust are its continents.
Extreme pressure causes the inner core of the Earth to remain solid.
The crust of the Earth is much cooler than its other layers.
The Earth’s mantle is flexible and shifts under heavy loads.
The core is where geologists look for oil, gas, and other resources.
The crust and the upper most part of the mantle make up the lithosphere.
Convection currents occur in the upper layer of the mantle called the mesosphere.
Copyright 2009 LessonSnips www.lessonsnips.com