This demonstration illustrates the properties of the mantle of the Earth, using potty putty mixed with a solution of borax and simple glue. When left on the desk the potty putty will sink and spread. However it will also bounce like a ball if enough borax is used and it can be stretched far more than plasticine if pulled gently, but can also be fractured if pulled suddenly. Students will discover that they should not assume that the Earth's mantle must be liquid just because they see liquid (lava) emerging from volcanoes. In fact the mantle is almost entirely solid but the forces on it allow it to flow, much as the force of gravity can cause the potty putty, which is solid, to flow.
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