Learnabout.co.uk Geography - Volcanoes and Earthquakes

The earth isn't just a lump of rock. It's a complex thingumie of ultra-hot magma in the middle with a toasty mantle around it, all wrapped up by a tiny, but nice and cool, crust.

Thin crust around hot mantle with magma core

Lava LampBecause of all that, it doesn't stay still. (Well, would you sit still if you were at 3000°C?) The heat from the core pushes the mantle (which is, believe it or not, a sort of liquid) towards the surface (hot things rise) where it cools down and starts to sink again (just think of a lava lamp).


The mantle flows

This constant changing pushes the crust around, resulting in...

Continental drift

Countries just can't stop moving. They're constantly whizzing around at the astounding rate of, er, 2cm a year. That might seem incrediblty slow, but you have to remember that they weigh thousands of tonnes, so they can't move as quickly as you can.
Millions of years ago, all the countries were one big lump of land near the north pole. Now, they're spread all around the globe. So you can see that while they may move slow, they can go a very long way.

The thing is, it's hard to move thousands of tonnes of continent. It takes a lot of pushing power, which the earth just doesn't have. So the smaller forces build up over a long time, until suddenly...

Earth quake!

After an eathquake - this building wasn't strong enoughThe continent will grind it's way along, rumbling as it goes, shaking everything on it to peices unless it's strong enough.
This is why buildings in earthquake zones are made stronger. If they're too weak, they end up looking like the picture on the left.


Another result of the mantle moving around is...

Volcanoes

Now, volcanoes are nasty neibourghs. Every couple of hundred years (sometimes more frequently, sometimes less) they turn up the music to full blast, pump toxic gas into the sky and throw tonnes of mud everywhere, in one giant eruption.
Things to know about eruptions:
  • First, the ground shakes as the magma tries to push up through the surface
  • Then, with a deafening BOOM, the top of the volcano explodes, throwing mud everywhere
  • Soon after, toxic gases and mud start pumping into the sky forming black clouds and surrounding the landscape in darkness
  • And finally the red-hot magma pours out (and is called lava once on the surface), slowly spilling down the mountain
After the eruption, the lava will cool down and become normal rock. This makes the volcano get bigger each time it errupts. Sometimes the top of the volcano (also known as the cap) will land beside the main cone, and form a smaller hill.

This animation shows what happens:




And that's all there is to it. Now ask your teacher for some worksheets, or if you prefer (let's face it, who wouldn't?) play the game!
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