Orange Mound Spring
March 30, 2004
The photo above shows the Orange Mound Spring in Yellowstone National Park, Wyoming. Unlike many of the other hydrothermal features of the park, Mammoth Hot Springs sits on layers of limestone. Weakly acidic water dissolves calcium carbonate (CaCO3) from the limestone; this then is deposited at the surface in the form of travertine. Travertine is naturally white. However, various bacterial thermopiles thrive in the sulfur rich waters throughout Yellowstone giving a number of features, such as Orange Mound Spring, its distinctive coloration.
Although the last major eruptive episode in the Yellowstone region was nearly 640,000 years ago, Yellowstone continues to be one of the most volcanically active areas in the U. S. Yellowstone National Park, the nation’s first National Park, sits above the Yellowstone hot spot. Water from rain and snowmelt seeps through the rock layers and is heated by the partially molten rock of the remaining magma chamber.