Two factors essential to create geysers are missing here: geysers require superheated water, and they need rock harder than the limestone to provide the required plumbing and buildup of pressure. Colors and Patterns in the Terraces Some of the bright colors in the runoff come from mineral deposits, but most come from microorganisms that thrive in hot water. These microorganisms begin to appear just a few days after a new spring is born. The resident bacteria and algae help extract some of the carbon dioxide from the hot spring water. Calcium carbonate is precipitated on top of the organisms, which in turn seek sunlight and begin to build up above the mineral deposits. Looking closely, you can find filamentous patterns in the formations, showing the results of this precipitation and growth. Inactive terraces are white; long-inactive ones are various shades of gray. What makes the springs that build the terraces so unpredictable?
The accumulating travertine tends to clog the plumbing, and varying water supply, chemistry, temperature, and frequent earthquakes may also contribute to the changes. Some Facts and Figures about Mammoth Hot Springs Every day at Mammoth an estimated 1.4 million gallons (5.3 million liters) of water is discharged and about two tons of new travertine are deposited. However, Mammoth is not the world’s largest set of active travertine terraces; a larger one, Pamukkale (ancient Hierapolis) in southwestern Turkey, covers several square kilometers, and there may be others. Besides the large terraces, other types of travertine features at Mammoth Terracettes forming on Lower Hymen Terrace (2000) are cones, such as Liberty Cap; fissure ridges, that is, mounds of travertine fed by water rising through cracks along their center plane; and terracettes. Terracettes are the individual semicircles of travertine formed at the edges of a hot spring pool. In over 100 years of observation, geologists have concluded that the overall thermal activity has neither declined nor increased. Over time, some hot springs seal themselves and never reopen, others cease and resume, and new ones appear with no warning.