Natural geysers form when underground chambers fill with water and are heated geothermally. When the water is heated to its boiling point, the geyser erupts, spewing its contents—and the cycle starts again.
A large hanging lens creates upside-down images of distant objects and right-side-up images of nearby objects. You can locate the upside-down images by using a piece of white paper as a screen. The right-side-up images are harder to find.