Lava lamp. Glowing lava lamp, an ornamental novelty. This lamp consists of an encased mixture of two immiscible liquids (liquids that will not blend together). These liquids have similar but not identical densities. When the light bulb (not seen) at the base of the lamp is switched on, the liquid nearer the base of the lamp (the more dense liquid, red here) will heat up. As it heats, the liquid will expand and become less dense and consequently rise. As it cools it becomes more dense and will thus fall. This process causes the lamp to display peculiar light patterns.