File:Little Anemone Geyser eruption (background) & Big Anemone Geyser (foreground) (2-21-2-24 PM, 1 June 2013) 01.jpg

English: Geysers are hot springs that episodically erupt columns of water. They occur in few places on Earth. The highest concentration of geysers anywhere is in Yellowstone’s Upper Geyser Basin (northwestern Wyoming, USA).

Little Anemone Geyser is a frequently erupting small geyser in the southern Geyser Hill Group. It is immediately adjacent to Big Anemone Geyser - together they make up “Anemone Geyser”. Little Anemone has a nearly circular basin about 2 meters in diameter, floored by light grayish to pinkish-gray nodulose geyserite, and rimmed by dark brown nodulose geyserite. Geyserite is a friable to solid chemical sedimentary rock composed of opal (hydrous silica, a.k.a. opaline silica: SiO2•nH2O), It forms by precipitation of hydrous silica from hot spring water. Geyserite is the dominant material at & around Yellowstone hot springs and geysers (the Mammoth Hot Springs area is a major exception to this). The silica in the geyserite is ultimately derived from leaching of subsurface, late Cenozoic-aged rhyolitic rocks by superheated groundwater. Rhyolite is an abundant rock at Yellowstone.

Little Anemone Geyser has frequent, low to moderately low splashing eruptions. Eruption durations vary considerably, from less than 1 minute long to almost 20 minutes. Intervals between eruption starts also vary. Eruptions usually start with slow to moderately slow pool filling. Eruption cessations are followed by halting, partial pool drains or complete pool drains. Crescentic-shaped eruption splash pools rim Little Anemone Geyser’s basin. Runoff and overflow from eruptions drain southward toward the Firehole River - some of it ends up in Cascade Geyser’s pool. Extremophile microbial mats coat much of the perimeter of Little Anemone Geyser’s basin and runoff channels.