Download Earth Layers Worksheet

8th Grade Science
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The Layers of the Earth
Earthquakes
Most of the information scientists have gathered about the Earth’s interior has come
from studying earthquakes. Earthquakes happen when a part of Earth’s outermost layer
moves all of a sudden. Earthquakes produce shock waves that travel through the Earth.
These shock waves, which are waves of energy, are called seismic waves, and they are
recorded by a special instrument, called a seismograph.
All earthquakes produce at least two different types of waves at the same time: P waves
and S waves. By determining the speed and direction these waves are traveling,
scientists can determine how Earth’s interior looks like.
Earth’s Interior
The Earth is made up of several different layers. It is believed that as the Earth cooled
the heavier materials sank towards the center of Earth, the lighter materials moved into
the middle of the Earth, and the lightest materials of all rose to the top. This explains
why things like rock are on the surface of the Earth and the much heavier things like
iron are located in the Earth’s core. How many layers there are depends how you look
at it. There are three main layers but you often read that there are 4, counting the inner
and the outer core as a different layer.
The Layers of the Earth are:
• The Crust – the part of the Earth that you live on.
• The Upper Mantle – the upper part of the Upper Mantle together with the crust make
up the Lithosphere. The lower part of the Upper Mantle is the astenosphere. The
astenosphere is partially liquid and causes the movement of the lithosphere.
• The Lower Mantle – This layer is solid
• The Outer Core – liquid metal
• The Inner Core – solid iron
The Crust
Think of the crust like you would of the peel of a fruit. This area isthin compared to the
rest of the layers. The thickness of the crust varies. Crust beneath the ocean, called
oceanic crust, is less than 10 km thick. That is about the distance from Makawao to
Pukalani. Crust beneath the continents, called the continental crust, is about 32 km
thick. That is about the distance from Makawao to Lahaina.
The crust and the stiff upper part of the mantle together make up the rocky lithosphere.
The crust and the whole lithosphere are broken into many different parts called plates.
These plates ‘float’ on the softer part of the upper mantle, called the astenosphere. This
allows the plates to move. Occasionally they will stop moving but when they stick in one
place they build pressure until they snap. When they snap an earthquake occurs.
The crust of the Earth is made of rock. There are two main types of rock that the Earth
is made of, granite and basalt. The oceanic crust is made of basalt, which is a form of
lava (volcanic) rock. The continental crust is made of granite. The oceanic rock is much
denser and heavier than the continental rock. As the continental rock is not as heavy,
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plates carrying the continents usually slip over the plates carrying the oceans.
The Mantle
The mantle is the largest layer of the Earth. The mantle si made up of extremely hot
rock composed of the elements silicon, oxygen, iron, magnesium and sulphur. The
boundary between the crust and the mantle is called the Moho. Here the temperature of
the Earth is about 870°C. As you get deeper into the mantle the temperature rises until
it reaches a top heat of around 2200°C at the bottom of the lower mantle.
The mantle can be divided into the lower mantle and the upper mantle. The lower
mantle is solid because of the high pressure. The upper mantle again can be divided
into two layers, the liquid lower layer called the astenosphere and the stiffer upper part.
The stiffer upper part together with the crust forms the lithosphere.
The lithospheric plates of the Earth move because the mantle moves. Because the
mantle is such a dense material, the plates can drift along on top of the upper mantle,
similar to how oil might float on top of water. Scientists believe, the flowing occurs due
to convection currents. Convection currents are caused by hot material in the bottom of
the mantle rising up, cooling, and sinking to the bottom again. As it gets to the bottom it
again becomes hot and repeats the process continually. This current drags the
lithospheric plates along.
Outer Core
The outer core starts at 2900 km (1800 miles) beneath the surface of the Earth and it is
about 2250 km thick. At its hottest point the outer core will reach a temperature of
5000°C. This is so hot that the entire layer is liquid. This area of the Earth is made up of
molten nickel and iron. This moving mass of molten medal together with the inner core
create Earth’s magnetic field.
Inner Core
The inner core is the final layer of the Earth. The inner core begins at 5150 km (4000
miles) below the earth’s surface. This is a little more than the distance from Honolulu to
Denver, Colorado or the Arctic Circle up in Alaska. The inner core is about 1300 km
(800 miles) thick. The highest temperature in this layer is 5000 °C. At this temperature
the iron and nickel that make up the inner core would be liquid were it not for the intense
pressure in this layer. Because of the pressure the inner core is solid.
8th Grade Science
Team Na Ali’i
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The Layers of the Earth Worksheet
How do scientists know what Earth’s interior looks like?
Why does the Earth have layers?
What is the difference of oceanic crust and continental crust?
(Thickness, rocks, which one is heavier).
What is the boundary between crust and mantle called?
What are the different parts of the mantle? (3)
What is the Lithosphere?
What is the Astenosphere?
Which layers are liquid and which are solid?
Explain convection currents based on what you’ve read.
Label the diagram on the other side of this paper!
8th Grade Science
Team Na Ali’i
Ocean
Oceanic Crust
Continental Crust
Moho
Lithosphere
Upper Mantle – Lithosphere
Upper Mantle – Astenosphere
Lower Mantle
Outer Core
Inner Core
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