Air bubbling up through sand creates the impression of a volcanic landscape. Pools of air and sand, acting like underground chambers of hot rock, rise through the denser material above them and erupt on the surface. Visitors can move the lever to change the rate of air flowing through the sand. At high flow rates, the entire mass of sand becomes fluid, like water, though no water is present. "Caldera" displays a cross-sectional view of how an actual volcanic dome might develop and collapse.