Well, technically speaking it's a volcano in a tea cup, or a glass coffee mug, but let's not split hairs here. It's a cup, it's storm and I had fun making it.
This is a model re-enactment of ...
... how volcanoes work.
Put some wax in the bottom of a fireproof glass container.
Add some sand.
Fill it up with cold water.
Now carefully heat the bottom.
Eventually, the wax underneath starts to boil (representing the moulten rocks under the Earth's crust) and it begins to lift the whole landscape above in a dome shape.
Then, the moment of truth - the pressure becomes too much and at the weakest point, where the sand has bubbles, the hot wax shoots out in a lovely volcanic explosion. The entire wax reservoir empties and you get a lovely effect of a flattened top as well, representing how material from the volcanic explosion forms a layer of ash in the atmosphere.
Great fun to do, and it's true - I've always want to make a storm in a tea cup!
What do you think of this experiment?