Mount St Helens

Mount St Helens is one of several active volcanoes that make up the Cascades Range on the west coast of the USA. These have erupted on several occasions in the last 4000 years (see map).

Image credit – USGS

Tanno and Iguda have been looking into the famous 1980 eruption of Mount St Helens.

The 1980 eruption was a very important event in helping to understand volcanoes.
Find out about what happened at Mount St Helens in 1980 by the scientists that were on the ground monitoring it with the short video from the United States Geological Survey (USGS).

Image/video credit: USGS.
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Before and after Mount St Helens images. Image Credit – USGS

The volcano was so explosive that almost half the mountain was lost during the eruption as you can see from the before and after images of Mount St Helens.

A New Volcano Grows!

Dr Volcano visited the volcano in 2001 and you can see from his image that a new volcanic dome was growing into the crater area. The volcano continues to grow back towards a full mountain. (image Credit – Dougal Jerram).

Tanno and Iguda have discovered that one of the other famous Cascades volcanoes (Crater Lake) was formed by the eruption of an ancient volcano called Mount Mazama some 7700 years ago. The eruption caused the volcano to collapse into what is called a ‘Caldera’, where the lake now sits (shown below).
You can see how a caldera can form with your activity ‘Create your own Caldera’

The formation of Crater Lake caldera, with a view into present day lake and a computer construction of the ‘drained’ lake in 3D.
Image Credit – adapted from USGS


Create your own Caldera. using inflation and collapse you can create your own caldera.

Here you can use some simple movements of inflation and deflation to simulate a magma chamber filling and then collapsing when it erupts to create a caldera.

  • You will need:
    1) A box to hold your experiment in.
    2) A balloon and pump.
    3) Some flour to represent the ground in your model.
  • Place the balloon in the bottom of the box and have neck of the balloon poking out of the box so you are able to pump it up. This may be also achieved with the use of a pipe.
  • Set your balloon to have a small amount of air inside but do not blow it up yet.
  • Fill the box with floor so that your balloon is covered and that there is a layer of a few centimetres of flour above the balloon.
  • You can now start to inflate your balloon and you will se the surface of the floor deform.
  • once you have inflated it for a bit you can take a picture of your inflated ‘volcano’. Note all the cracks and ground movement that has happened….
  • Now let the air out of the balloon as if the magma was erupted out of the volcano.
  • The floor should now collapse forming a ‘caldera’ depression.
  • If you want you can put some coloured lines on the top surface (e.g. with food colouring) to help you see the deformation and movement of the flour.

Below is an example of this experiment by the USGS to help give you some ideas as to how you can set it up…

You can go to the previous Volcanoes secret pages by clicking the places below.

StromboliVesuvius/PompeiiErta Ale