Hi there - this is P again after a Saturday Science session on volcanoes. We've always wanted to make a volcano and it seemed like a great way to get back into some Saturday Science after getting out of the routine for a few weeks. We started by thinking about what's inside the Earth. It's very hot in there, so hot that rock melts and is called "magma". When magma breaks through the surface we call it "lava". All that separates us from the magma below is a crust of cooled, solid rock. How thick is the crust? H, R and K made their guesses on the picture above. It turns out, if the Earth were an apple, the crust would be about half the thickness of the apple skin! This is still tens of kilometres thick, but you get the idea.
The crust is broken into tectonic plates which float on the magma below. Where plates push into each other mountains form (like the Himalayas). A fun way to model this is with pancakes floating on maple syrup!
The pushing and rubbing also creates heat and releases trapped gas and this is why volcanoes often form where plates meet. Time to go outside and build some volcanoes!
Take a jar, surround it with soil, add some warm water, sodium bicarbonate, detergent and food dye. Then pour in vinegar and watch the eruption!
Vinegar reacts with the sodium bicarbonate to release carbon dioxide gas. This bubbles up in the detergent and causes a magnificent eruption. Heat causes carbon dioxide to be released also, which is what happens when you cook with self raising flour, and also when carbonate rocks are heated. Our homemade volcanoes erupted many times until at last our supplies ran out. It was a lot of fun. We finished with a great National Geographic video of real volcanoes in action.
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