How did this volcano get here?
  • "This volcano" is Mt Victoria, in Devonport, Auckland
  • A volcano marks the point where molten rock, from deep within the earth, has reached the earth’s surface.
  • As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up “fissures” which are narrow cracks in the earths crust. This molten rock is called magma.
  • Once the magma erupts through the earth’s surface it’s called lava. And as the built up lava flows cool and harden into hills we call this a volcano.
  • The type, viscosity (runniness) and density of magma and how it erupts decides what shape forms on the earth’s crust. If the lava is thick and sticky and oozes from the earth’s crust it will travel like flowing porridge and just add a thick layer to the earth’s crust. If it’s thick and sticky and fountains upward it will make the typical volcanic cone shape.
  • The top layer of the built up lava flow cools and hardens as the underneath stuff continues to ooze and cool slowly.
  • Mt Victoria was formed hundreds of years ago when the pressure of the magma about 100 kms below the earth’s surface forced the magma up and out into a volcano.
  Did You Know?
  • If we could have a bird’s eye view of Mt Victoria we would see that it is a horseshoe shaped volcano. The first eruptions made a nice round cone shape. One side of the volcano collapsed when the lava flow erupted more fiercely from one side.
  • Volcanic eruptions vary in force from gentle to violent depending on how much pressure is built up in the magma from gases.
  • Auckland is built on a volcanic field - a place where there has been lots of volcanic activity. Mt Victoria is one of 50 volcanoes in the Auckland area.
  • The largest volcano in the world is Mauna Loa in Hawaii and it's at least 10 kilometers tall!
Make your own volcanic eruption

What you need:
A small plastic container with a lid (like an old film canister)
Some water
An antacid tablet
A space outside

What you do:
First of all fill the container with water until it is half full. Have the lid handy because as soon as you put the tablet into the water you’ll need to put the lid on. Once the lid is on put the container on the ground and move a way from it – quick as you can – about 2 meters.

What happens? The lid should come flying off the container. The as the antacid tablet dissolves in the water it produces carbon dioxide. The carbon dioxide gas builds up in the container until there is too much and the pressure is strong enough to push the top of the container off.
That’s what happens to the earth when the hot magma wants to come out. And that’s how a volcano is made.

Under Pressure

What you need:
An adult to help
2 small bottles full of a fizzy drink.
A place outside where it doesn’t matter if you make a sticky mess :-)

What you do:
Shake one of the bottles hard. Predict what will happen when you unscrew both the lids at the same time. Try it and see. Can you explain the different results?
The fizz is carbon dioxide that has been squashed in there under pressure the more you shake the bottle the more pressure the carbon dioxide is in and it wants to get out!
Make a volcano

What you need:
A sandpit
2 tablespoons of baking soda
Half a cup of vinegar

What you do:
Make a volcano shape in the sand and hollow out a well in the top of the volcano. Put in the baking soda and then pour in the vinegar.
The vinegar reacts with the baking soda to make a chemical reaction and bubbles out over the top of the sand volcano just like a real one does.

Are there any volcanoes in your region? Maybe they’re extinct like nearly all of the ones in Auckland? Or maybe they’re active like Mt Ruapehu or White Island. Find out more about these amazing acts of nature.
What does a volcano wear when it goes out to town?
A LavaLava.
From Jo Wheat

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