Mudpots, also called mud pools and paint pots, are puddles of hot bubbling mud. Like other hydrothermal features, mudpots are heated by molten rock or magma found a mile or more underground. Unlike geysers and hot springs, mudpots have almost no water. They release gases instead. Gases cause mudpots to bubble and burst. Gases create the plopping sound. Gases produce the rotten egg odor. Gases dissolve rock and make a muddy clay. But gases don't paint hot mud pools. Mudpots get their color from minerals. Sulfates paint mudpots yellow. Iron compounds stain mudpots red and brown. Colored mudpots are known as paint pots.