Composition of the Earth

The Earth is made up of all different kinds of layers and parts and some of the parts are always moving.

The layers get thicker when you get closer to the core of the Earth.

The Earth has four main layers and they go in this order from outside to inside:

  • Crust
  • Mantle
  • Outer Core
  • Inner Core

Geologic layers of Earth

The Crust

The crust is the outermost layer of the Earth.  This layer is thinner than the other layers and it is about 5 kilometers to 70 kilometers thick.

We live on what is called the continental crust which is part of the layer of the Earth.

The crust combines different types of rock, such as Igneous rocks, Sedimentary rock, and igneous.

The continental crust is made up of different rocks but mostly of silica and alumina.  The silica and alumina of the Earth’s Crust are called “sial.”

The crust is the layer of the Earth that people live on.  The crust also has the sea, soil, mountains, oceans, and more.  The crust is around 305 miles thick in the ocean.

More facts about the crust:

  • Made from basalt rock
  • Around 25 miles thick
  • Made of granite rock
  • The only layer that can be drilled to be explored.

The Mantle

The mantle is the part of the Earth’s that is between the crust and the outer core.  The mantle is thicker than the crust and can be over 3000 kilometers thick.  This part of the Earth is made up of silicate rocks that have a lot of magnesium and iron in them.

Many scientists put the mantle into two different categories; the upper mantle and the lower mantle.

There are only tiny differences between the two mantles.

The main difference between the upper and lower mantle is that the upper mantle has a special rock called olivine.  Olivine is made up of silicon dioxide and peridotite.  Peridotite is very heavy rock.

The lower mantle is stronger and is solid.  It is made up of:

  • Ovalene
  • Iron
  • Magnesium
  • Silicate

The mantel has semi-solid rocks that can turn into liquid if there is enough pressure.

When the rocks get very hot and then get very cool, it causes them to sink back into the core and this is what causes the crust to break into different plates and sections.

When these plates and sections move, it is what causes there to be different things that happen on the Earth such as earthquakes and volcanic activity (molten rock and melting lava to flow).

Earth's major plates

Plate Tectonics

When there is a different movement of the crust and the plates, it is called plate tectonics.  Plate tectonics is the cause of earthquakes, tsunamis, and volcanic activity.

When the plates move, they cause mountains and floors in the sea to be formed.

Sea floors are made of basalt, a rock that is very thick.  When the rock is formed, it presses into the mantle and this can cause it to fill with water.

Plate tectonics is part of the creation of continents because continents are formed when plates move and are formed together.  These are formed and moved because of icebergs and other movements.

The Core of the Earth

The core is made up of two different layers:

  • The outer core
  • The inner core

When the Earth has formed billions of years ago, the part of the Earth that was formed that was the heaviest part went to the middle of the Earth and this is how the inner core was formed.

The other substances that were lighter and flowier stayed on the top of the Earth or stayed at the crust of the Earth.

Since the heavier materials went to the middle, this made the inner core almost solid which is what makes it so heavy and thick.

The Outer Core

The outer core is located between the mantle and the inner core of the Earth.  The outer core is mostly made up of nickel and iron and is more than 4000 degrees Celsius, so it is extremely hot.

The nickel and the iron are in liquid form because of it being so hot in the outer core.

The outer core creates a magnetic field, just like the North and South Pole do.  The magnetic field helps to protect the Earth from so much solar radiation and from solar winds that could damage the Earth.

The magnetic field of the outer core goes all the way into space, so the Earth is very protected.

More facts about the outer core:

  • Sphere shaped
  • Molten iron or Fe
  • Lots of pressure
  • Magnetic
  • 3,200 miles thick.
  • Between 7,200 and 9,000 degrees Fahrenheit.
  • The flowing metals are what cause it to be magnetic.

The internal structure of Earth

The Inner Core

The Inner Core is located inside the outer core.  Like the outer core, the inner core is also made up of nickel and iron but instead of it being a liquid, it is solid.

Even though the inner core is very hot just like the outer core, there is a lot of pressure that is applied from all of the other Earth’s layers.  Because of the pressure, it causes the nickel and the iron to be solid.

The inner core, even though the nickel and iron are solid, it is the hottest part of the Earth and it is over 5000 degrees Celsius.

More facts about the inner core:

  • More pressure
  • Very dense
  • Very compact
  • Heavy matter
  • Elements of iron but not pure iron
  • Around 1,500 miles thick.
  • Between 9,000 and 13,000 degrees Fahrenheit
  • Always spinning at a different speed than the rest of the Earth.

What is Happening to the Structure of the earth?

Inside the Earth are things that are happening such as seismic waves.  The waves are caused by things that are going on around the Earth such as volcanic explosions, earthquakes, ocean movement, and more.

When these things happen, it causes seismic waves to move.  There are two types of seismic waves:

  • Shear wave-A shear wave is a wave that does not travel through anything that is liquid or wet.
  • Pressure Wave – A pressure wave will move through both solids and through liquids.

The seismic waves cause energy to travel through the different layers of the Earth.  When these waves move, things can happen like the magma can move, tectonic plates move or landslides can happen.  These energies cause different reactions from the waves.

When scientists study these waves, they use a machine that is called a seismograph.

Composition of the Earth Facts:

  • The layers of the Earth are always moving.
  • The Earth is made up of mostly rock and metal.
  • The way that the inner core spins is what causes there to be a magnetic field.
  • When people explore the Earth’s mantle, it is from the seabed because that layer is thinner than the layers of the mantle that are on the land.
  • The first explorer explored the mantle in 1996 but gave up because the area was so thick and hard to drill through.
  • The inner core and the outer core are as big as the planet Mars.
  • When a meteorite lands, it contains iron and nickel.  Some scientists believe that meteorites are rocks from other planets.
  • Some of the layers of the Earth are made up of even more layers.
  • The mantle is made of rock that is solid but at the same time it could be molded much like clay.
  • There is an area between the crust and the mantle that scientists have called mojo.

What Did You Learn?

  • What are the different parts of the Earth?  The Earth is made up of different parts such as the crust, the inner and outer core, and the mantle.  Each part is made up of different metals and rocks.
  • What is the most inner part of the Earth called?  The most inner part of the Earth is called the inner core.  The inner core is very hot, but it is solid in the middle because of all of the pressure.
  • What is special about the outer core?  The outer core is made up of the same metals as the inner core, but the outer core is liquid and is similar to hot magma.
  • What pare of the Earth do people and animals live?  People and animals live on the crust of the Earth.
  • What are the waves called that are always moving and that are caused by things such as earthquakes?  The waves that are moving inside of the Earth are called seismic waves.  These waves are energy waves that happen from movement on the Earth.