What are geysers and how are they formed?

1) What are geysers?
A geyser is a hot spring that periodically erupts, throwing water into the air. Though that sounds simple, geysers are extremely rare. As of August 2008, the total of active geysers on earth numbered approximately 1000.
Conditions must be just right for geysers to occur. Three components must be present for geysers to exist: an abundant supply of water, an intense source of heat, and unique plumbing. Water is common in nature, heat can come from volcanic activity, but the plumbing is critical. For water to be thrown into the air, geyser plumbing must be water- and pressure-tight. Geyse scientists and observers have identified the volcanic rock rhyolite as being particularly effective at hosting geysers. Rhyolite is high in silica, which can deposit a water-tight seal along the walls of the geyser plumbing. Most of the geyser fields in the world are found in rhyolite or similar silica-laden rocks (like ignimbrite). The mixture of water, volcanic heat, and plumbing is exceptional at Yellowstone National Park. Over one-half of the world's geysers are located within the park's boundaries.
It is increasingly apparent that geysers must possess a fourth characteristic to exist: remoteness. Within the last fifty years, volcanic heat and abundant water have been increasingly harnessed to turn turbines for electricity production. Geothermal energy can be produced at any site where volcanic heat and water are readily available. Unfortunately, geyser fields are ideal for this type of energy production. Geothermal energy production steals the geysers' water, and destroys geyser activity (for example, Wairakei, New Zealand). A growing threat to geysers stems from mineral extraction. Hot groundwater may precipitate gold or other valuable minerals, and extraction may require removing the geyser plumbing itself. For example, in May 2003, mineral exploration at South America's second largest geyser field (Puchuldiza, Chile), caused cessation in the field's geysers. Few realize the actual rarity of geysers. As a result, many geyser fields have been destroyed and many others are being threatened.
2) How are geysers formed?
Water- A Needed Component in Geyser Development
Superheated water is the needed in order for geysers to form. The heat comes from a buried magma chamber in an volcanic setting. Water is more easily obtained than the heat. The water comes from the groundwater system in the geyser basin. It starts as precipitation and enters the ground water system by percolating down through porous sand and gravel as well as cracks and fissures in the earth. The surface water recharges the water that circulates in the subsurface and is eventually erupted from a geyser or flows out of hot springs. The water does not need to necessarily be present in great volumes on the surface. Geyser do occur in desert environments. In fact some the geysers in Chile occur in one of the the driest valleys in the world. What is important is that water is available, and that it can circulate deep into the earth's surface where it can approach the heat source. It is estimated that it takes several hundred years for the water in Yellowstone to fall as rain or snow, enter the groundwater system, circulate deep down near the heat source and then rise to near the surface where some of it is erupted from geysers. Surface conditions such as droughts or extremely wet periods may not effect geyser eruptions or hot spring flow for hundreds of years. Cooler water in the near surface also mixes with the rising superheated water and may play a role in a geyser's eruption and timing.The heat needed for geyser formation comes from liquid rock or magma when it is near the surface of the earth. That is why geysers and volcanoes are found in the same area. When the magma reaches the surface, a volcano is formed. Geysers, though rare, are found in the same geologic settings where volcanic heat sources are available.Convergent plate margins occur where one of the earth's plates is being subducted under another. The friction causes the rocks in and around the subducting plate to melt and the molten rock moves toward the surface. The rising magma then forms volcanoes. Geysers in Chile, New Zealand, Russia, Mexico and Japan are found in this geologic setting. In Divergent Margins, where rifting is occurring, the plates are moving away from each other. In the oceans, the splitting of the crust or rifting allows magma to reach the surface. Molten rock spills to the surface along these fractures and new oceanic crust is formed. Sometimes continental crust is located at the plate boundaries where the plates are or are starting to move away from each other. On the continental crust when rifting occurs large cracks known as rift valleys form. As the heat from the mantle rises along these big cracks, magma forms and rises to the surface which, in turns, results in volcanic activity. Geysers are found along divergent margins or incipient rift basins where continental crust is involved. Examples of geysers in this setting are found in Iceland, Nevada, and Kenya.
Done by : Maverique
Register number : 31