File:Giant Geyser (early afternoon, 31 May 2013) 18 (13893151271).jpg

Geysers are hot springs that episodically erupt columns of water. They occur in few places on Earth. The highest concentration of geysers anywhere is at the Yellowstone Hotspot Volcano in northwestern Wyoming, USA.

Giant Geyser has the second-tallest eruptions of any geyser on Earth (# 1 is Steamboat Geyser). Giant’s eruption columns reach between 200 and 300 feet high, with a water output estimated by park signage at about one million gallons. The geyser is the namesake of the Giant Group in Yellowstone’s Upper Geyser Basin. It is the prominent feature in the Giant Platform, which is located on the western banks of the Firehole River, north of Oblong Geyser and south-southeast of Grotto Geyser.

Giant is a cone-type geyser with a massive geyserite cone about 7 x 9 meters in plan view and about 4 meters tall. The upper half of the cone has a breached, somewhat subcylindrical shape. The visible interior of the upper vent has geyserite with a very coarsely scaled morphology.

Very low to moderate-sized splashing occurs frequently in Giant Geyser, sourced from a northern side vent within the throat of the geyser. Splashing usually extends from lower left to upper right, when viewed from the observation platform ("Giant Cage").

Major eruptions of Giant Geyser do not typically occur at regular intervals. Many years can elapse with no eruptions. During some active seasons, major eruptions occur about once a week. Eruption durations are about 1 to 1.75 hours. “Normal function” eruptions are shorter in height (100 to 200 feet), whereas “Mastiff function” eruptions are taller (200 to 300 feet). The latter are accompanied by prominent eruptive spouting from nearby Mastiff Geyser.

Video of Giant Geyser, including a major eruption: