Orange Mound Spring is one of the several

hot springs A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

Yellowstone National Park Yellowstone National Park is a List of national parks of the United States, national park of the United States located in the northwest corner of Wyoming, with small portions extending into Montana and Idaho. It was established by the 42nd U ...

. The name comes from its dark orange appearance caused by orange

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

living on the

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process ...

, the rock that it is made of. The Orange Mound Spring is part of the

Mammoth Hot Springs Mammoth Hot Springs is a large complex of hot springs on a hill of travertine in Yellowstone National Park adjacent to Fort Yellowstone and the Mammoth Hot Springs Historic District. It was created over thousands of years as hot water from the ...

area of the park. The Orange Mound Spring is arguably most notable for its prominence above the ground, compared to the rest of the Mammoth Hot Springs, which are mostly flat and leveled terraces. It was named by early Yellowstone assistant superintendent and guide, G.L. Henderson.

Flow, age and color

The Orange Mound Spring is thermally cooler (~170˚F) than most springs in Yellowstone and at the Mammoth Hot Springs themselves, allowing the orange-tinted cyanobacteria to thrive and color the spring a darker shade of orange than the rest of the Mammoth Terraces. Depending on the nutrients that the bacteria receive, the color may change throughout the year. The Spring is said to be very old due to the shape and size of the mound as well as how little water flows out of the spring itself. It has created other nearby cone-shaped springs from itself due to the travertine deposits wearing away. Often in the Mammoth Hot Springs, flow will turn on and off, so on some days it may have no flow at all, and others it may have a lot.

References

Yellowstone National Park Geysers of Wyoming Yellowstone Caldera Geothermal features of Yellowstone National Park Geothermal features of Park County, Wyoming Landforms of Park County, Wyoming {{Wyoming-geo-stub