Download Layers of the Earth - Mrs. Rasmussen Science Class

An Overview
The Earth is made of 5 main
internal layers and one
external layer (the
atmosphere). This diagram
shows the locations and
approximate thicknesses of
each internal layer.
The Atmosphere
Technically, the very outermost layer of the Earth is
the one that we live in—the atmosphere. The
atmosphere contains all the air we breathe and the
weather we experience. Although we often use the
term “air,” the atmosphere is made out of many gases
like: nitrogen (78%), oxygen (21%), and other gases
like argon and carbon dioxide (1%). Since there isn’t
a distinct boundary between the atmosphere and
outer space, it is generally stated that the atmosphere
is around 100 km thick but it can extend up to 480 km
if you count the very thinnest parts. Temperature
also varies a great deal in the atmosphere, depending
on what altitude you are at but it can get as cold as 90° C.
The Crust
The crust is the rocky, outermost layer of the earth.
Oceans and soil sit on top of the crust. This layer is
divided into two types: oceanic crust and continental
crust. The crust is relatively thin compared to the
earths others layers. Oceanic crust averages 7 km in
thickness, while continental crust can be as thick as 100
km. The temperature of the crust at the surface
depends on where you are at. But the temperature of
the crust can be up to and 400 degrees Celsius in its
deepest parts. The crust is completely solid and is
composed of rock with many less dense elements like
oxygen, silicon and aluminum.
The Asthenosphere (Upper Mantle)
Below the crust is the mantle. The top part of the mantle
is a special layer called the asthenosphere or upper
mantle. The asthenosphere is about 180 km thick and
much hotter than the crust (about 500 degrees Celsius).
While it is technically still a solid, the rock in this layer is
hot enough and under enough pressure that it flows like
asphalt. A solid that can flow like this is called a plastic.
Another example of a plastic is silly putty. The fact that
the asthenosphere is a plastic has a major impact on the
crust. It is this layer that causes the tectonic plates of the
crust to move and, therefore, is the reason why we have
earthquakes. This layer is composed of rock that has
significant amounts of denser materials like calcium,
magnesium and iron.
The Mantle (Lower)
The lower or main part of the mantle is the largest layer of
the Earth and is about 2300 km thick. The temperature in
the lower mantle is much greater than the upper mantle
(about 2000 degrees). Even though this layer is hotter than
the asthenosphere, the lower mantle is actually a solid. It
is a solid because the great amount of pressure at this
depth keeps the molecules from moving like a liquid. The
lower mantle is composed of many of the same materials
as the upper mantle with the addition of a significant
amount of iron.
The Outer Core
The core of the Earth is divided into two parts. The outer
core lies beneath the mantle and can reach temperatures
up to 5000 degrees Celsius. Due to high temperatures, all
its components are in a liquid state. The outer core is
2200 Km thick. This layer is composed of melted iron,
melted nickel, and sulfur. Because it is liquid, it flows
constantly. This flowing metal in the outer core is
responsible for creating the Earth’s magnetic field. This
field surrounds the Earth and is important not only in
navigating, but in protecting us from harmful solar
radiation.
The Inner Core
The inner core is located at the very center of the earth
and is approximately 1200 km thick. Like the outer core,
it is composed of iron and nickel. The temperatures at
the core of the earth can reach almost 11,000 degrees
Celsius, that’s hotter than the surface of the sun!
Because of the immense pressure at the center of the
planet, the iron and nickel cannot flow and the inner core
remains a solid. The pressure is so powerful, that if you
were to journey to the center of the Earth, you would be
squished into something the size of a marble!
Patterns in Earth’s Layers