Layers of the Earth

The Earth is not just one big ball that’s solid throughout, although it might look that way! But it is made up of different layers, a bit like an onion. Each layer you peel off is made up of different things and they do different things too. Let’s get on with it and find all there is to know about the layers of the Earth!

What are the layers of the Earth?

The Earth is made of three layers. Let’s start from the outside and move our way in. The top layer, which is what we stand on is the crust, next comes the mantle and finally the core. Some of these layers are made up of even more layers and they’re always on the move. The Earth is mostly made of rock and metal. Scientists can’t exactly get in a rocket and head right to the middle of the Earth, or the core, so it’s difficult to know exactly what’s there. But being as clever as they are, they are always coming up with new ideas, and as measuring equipment becomes more advanced so they learn new things all the time.

What is the Crust?

The crust is an outer solid layer and this is where all life exists, including us, animals, mountains, sea and soil. It is about 8km thick in the ocean bed, which is called the oceanic crust. The oceanic crust is mostly made from basalt rock.

Then there’s the continental crust which is covered by land and is made mostly out of granite. Above that granite is sedimentary rock. Sedimentary rocks form over long periods of time and are made from debris, chemical sediment and broken rocks. It is between 5km to 70km thick.

The crust is the only later on Earth that scientists can study, as they can drill into it. So this is the layer that we know the most about!

But how do they study the crust? Well they watch how waves travel through the Earth, called Seismic waves, which are caused from earthquakes or eruptions.

They use a machine called a seismograph to study the waves.

What is the Mantle?

The next layer that comes is called the mantle and here’s all the info you need to understand this layer of the Earth.

The mantle is about 2,900km thick and amazingly it makes up about 85% of the Earth’s weight. Wow! That’s one heavy layer.

It is made molten, or melted, iron, minerals and other semi-solid rocks that will still flow under pressure.

In this layer the rocks rise. Those clever scientists think that when they rise from the very intense heat, and then cool down again, that they sink back to the core. This movement makes the crust break into plates, or different sections.

What happens when the crust breaks up into plates? Well they move and crash into each other and this causes earthquakes and volcanic eruptions. This movement is how new mountains and sea beds are formed. Wow, that’s interesting.

As we mentioned earlier, the oceanic crust is made of basalt, which is a really thick rock, and this can press into the mantle and then fill with water.

This is amazing. The continents were made from lighter blocks that float on the mantle like massive big icebergs.

How do they explore the mantle? This is usually done from the sea bed where the layer is thinner than it is on land. They first explored it back in 1996. But, they actually gave up as they just couldn’t get it right. In 2007 they drilled 7,000m below the seabed from a ship. This drilling was three times deeper than any other drillings that they’d done.

What is the Core?

Next up is the core! This is made up of two layers, the inner and the outer core. The Earth was formed 4.5 billion years ago, and when this happened, all the heavy materials sunk to the middle and this became the inner core. The lighter ones like air and water stayed on the top on the crust.

  • The inner core is kind of like a solid lead ball, which is about 2,400km thick. No wonder it’s like a solid lead ball! There’s heaps of pressure in the inner core, and that means it actually can’t melt. This is unbelievable!
  • The temperature in the inner core is between 4, 982⁰ and 7,204⁰C. That’s seriously hot, and just as hot as the surface of the sun. No wonder they can’t explore here, everyone would fry! Have you ever spilt some boiling water on yourself? Well if you have, you know it’s seriously sore! That water is 100⁰C. Now compare that to the inner core…can you even begin to imagine how hot it is?

The inner core apparently spins at a different speed to the rest of the planet and this causes the Earth’s magnetic field.

It is because of the flow of metals in the inner core that the Earth is magnetic. The effect of this magnetic field spreads way beyond the Earth and goes off far into space. It actually forms a barrier that helps protect the Earth from the Sun’s destructive solar winds. Wow that’s interesting.

The second layer of the core is made of liquid iron and nickel and is about 2,300km thick. As we don’t really know for sure, there are some people who think that it is 5,150km thick and between 3,982⁰C to 4,982⁰C hot! Whoa!

Some Other Interesting Facts

The mantle of the earth is solid rock, but amazingly it can be moulded, just like play dough. This certainly isn’t the type of play dough you’d want to play with; your fingers would burn as it’s so crazy, mad hot!

The inner core and the outer core of the Earth are as big as Mars! Now that’s something.




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