Geyser

A geyser is a special type of hot spring that from time to time spurts water above ground. It differs from most hot springs by erupting periodically, and its erupting water is generally nearly at boiling for pure water at sea level. Such features are very rare in the world, and they do not exist in Europe outside Iceland.

Two conditions underlie every geyser: a subsurface reservoir where hot water can reach boiling temperatures, and a constriction in the conduit that throttles and focuses erupting fluids. The constriction lets pressure build until an eruption releases it. Geysers are therefore just one type of hot spring, set apart from the rest by the plumbing that governs when they erupt.

Snowmelt and rain move down through rock layers, magma heats the water, the weight of water above builds pressure, and constrictions in the plumbing make water and steam explode with force. Pressure exerted by the enormous weight of the overlying water and rock prevents deep water from boiling. Confined steam bubbles lift water above the vent until the geyser splashes or overflows, which lowers pressure and triggers violent boiling; tremendous amounts of steam force water out of the vent, and the eruption stops when the water reservoir is depleted or the system cools. The rapid transition of water to steam underground drives both geyser eruptions and hydrothermal explosions.

Most geysers are very irregular in their behavior, and each is different in some respects from all others. At the park's elevation water boils at about 93 °C (199 °F), and water deep underground can rise well above that boiling point while remaining liquid under pressure, becoming superheated water with temperatures exceeding 400 °F.

Geysers fall into two broad categories according to the form of their vent and the manner of their eruption. A cone geyser discharges its water as a narrow jet, usually from a mineral cone built up around the opening. A fountain geyser throws water in various directions, typically from a pool rather than a raised cone. The same distinction can be read from the surface itself: eruptions may issue through narrow cones, through large silica structures, or from hot spring pools of the fountain type.

The rock that frames these openings is sinter, a common mineral deposit in thermal areas, made of silica dissolved from rhyolite and left behind when it precipitates from hydrothermal water. At the surface that silica precipitates as siliceous sinter, and deposits with bulbous or cauliflower-like surfaces are known as geyserite. Superheated water takes silica into solution underground and redeposits part of it around the vent, raising the distinctive cone. The same process leaves deposits in cracks, which help the system withstand the pressure required to produce a geyser.

Geysers are rare in the world, and Yellowstone contains more of them than anywhere else on Earth. The park holds more than 10,000 hydrothermal features, among them more than 500 geysers, which amount to about half of the world's geysers. Within one square mile the Upper Geyser Basin holds at least 150 of them. Geysers are especially abundant in the Lower, Midway, and Upper Geyser Basins near Old Faithful, and their intervals vary with changes in the subsurface plumbing.

The park's hydrothermal system is the visible expression of the immense Yellowstone volcano, which releases tremendous heat from an underlying partially molten magma body. The unique thermal features of Yellowstone inspired its establishment in 1872 as the world's first national park.

Among individual vents, Old Faithful is the standard reference point, erupting at average intervals of about 90 minutes for 1.5 to 5 minutes, expelling thousands of gallons of boiling water to heights of 106 to 184 feet (30 to 55 m). Yellowstone was inscribed as a World Heritage site in 1978.

Geysir in Haukadalur is one of the most famous geysers in the world, and its local name gave the word geyser to foreign languages. The Geysir area lies in the western volcanic belt of Iceland, which explains its geothermal activity. When Geysir was most active its eruptions spouted scalding water some 60 to 80 m into the air, and it has risen to 100 metres at its best. Seismic activity has sometimes stirred Geysir, which livened up again after the earthquakes of 2000 but was last known to have erupted in 2016 before settling back into dormancy. Strokkur does not empty between eruptions the way Geysir does, so it quickly refills and erupts at regular intervals, with eruptions that can reach up to 30 m in height every few minutes. Steamboat Geyser in the Norris Geyser Basin is the world's tallest active geyser: major eruptions shoot water more than 300 feet (91 m), plumes have been recorded above 115 m, and minor eruptions reach 6 to 40 feet (2 to 12 m). During the earthquakes of June 2000 the hot springs Konungshver and Blesi started to boil vigorously.

Te Puia in Rotorua is home to the world-famous Rotorua geysers, including the spectacular Pohutu Geyser.

Dolina Geizerov, the second largest geyser field in the world, lies within the Kronotsky Nature Reserve and is part of the Volcanoes of Kamchatka World Heritage site. The geysers of the Valley of Geysers were first discovered in 1941 and remained closed to commercial tourism until 1991 when the area opened to visitors. On 3 June 2007 a landslide buried a number of the valley's hydrothermal features, including the first geyser found there, Pervenets, under an estimated 180 feet (60 m) of debris, and created a natural dam on the Geyser River. The World Heritage Committee inscribed the Volcanoes of Kamchatka on the World Heritage List in 1996.

In sustained fieldwork from 1965 to 1971 Brock took samples from the hot pots, geyser pools, fumaroles and thermal basins of the Firehole River watershed, finding microbes in all of them, including a previously unknown species he named Thermus aquaticus with his colleague Hudson Freeze. The optimum temperature for growth of Thermus aquaticus is 70 °C and the maximum 79 °C.

In 1976 scientists at Cetus Corp. worked with enzymes from Thermus aquaticus, and Kary Mullis created a procedure called PCR that used the adapted enzymes, named Taq, to replicate DNA with great efficiency and precision. Kary Mullis browsed the culture collection and grew batches of Brock's Thermus aquaticus culture to find the enzyme Taq polymerase, whose heat resistance enabled him to rapidly and inexpensively copy genes.

Identifying the locations of hydrothermal features and monitoring their heat, water flow, and chemistry provides land managers with data for management decisions. Ground, airborne, and satellite thermal-infrared sensors can map and monitor hydrothermal activity within individual basins or over a broad region.

On 23 July 2024 a hydrothermal explosion beneath Black Diamond Pool in Biscuit Basin sent steam and debris hundreds of feet into the air and destroyed a nearby boardwalk. A rare eruption of Ear Spring on 15 September 2018 ejected foreign objects including coins and trash dating back to the 1930s. Boiling water surges just beneath the thin crust of most geyser basins, and people have been severely burned after breaking through the fragile surface.

• 15 March 2018
  Steamboat Geyser resumes activity
  Steamboat Geyser began a period of more frequent eruptions after three and a half years of dormancy.^{6Hydrothermal Systems · National Park Service (Yellowstone National Park) ↗}
• 2018
  Steamboat eruption count
  Steamboat erupted 32 times in 2018.^{6Hydrothermal Systems · National Park Service (Yellowstone National Park) ↗}
• 2019 and 2020
  Record years
  Each of 2019 and 2020 saw 48 recorded eruptions, the geyser's record years.^{9Steamboat Geyser · National Park Service (Yellowstone National Park) ↗}
• 2021
  Steamboat slows
  Steamboat slowed to 20 eruptions in 2021 and fewer in the years that followed.^{6Hydrothermal Systems · National Park Service (Yellowstone National Park) ↗}