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A hot spring is a spring whose water is hot. There are hot springs all over the earth, on every continent and even in the oceans. The groundwater emerging from hot springs is heated by geothermal processes.
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Definitions
There is, unfortunately, no universally accepted definition of a hot spring. For example, one can find the phrase hot spring defined as
a spring with water temperatures above its surroundings
a natural spring with water temperature above body temperature (normally between 36.5°C and 37.5°C, that is, between 97.8°F and 99.5°F )
a natural spring with warm water above body temperature
a thermal spring with water warmer than 98°F (37°C)
a natural spring of water greater than 70°F (21.1°C) (synonymous with thermal spring)
a natural discharge of groundwater with elevated temperatures
a type of thermal spring in which hot water is brought to the surface. The water temperature of a hot spring is usually 6.5ºC (11.7°F) or more above mean air temperature. Note that by this definition, "thermal spring" is not synomous with the term "hot spring".
a spring whose hot water is brought to the surface (synonymous with a thermal spring). The water temperature of the spring is usually 15°F (8°C) or more above the mean air temperature.
a spring with water above the core human body temperature (36.7°C or 98.06°F).
a spring with water above average ambient ground temperature, a definition favored by some.
a spring with water temperatures above 50°C (122°F)
The related term "warm spring" is defined as a spring with water temperature less than a hot spring by many sources, although Pentecost et al (2003) suggest that the phrase "warm spring" is not useful and should be avoided. The US NOAA Geophysical Data Center defines a "warm spring" as a spring with water between 20°C and 50°C (between 68°F and 122°F).
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Sources of heat
The water issuing from a hot spring is heated by geothermal heat, i.e., heat from the Earth's interior. In general, the temperature of rocks within the earth increases with depth. The rate of temperature increase with depth is known as the geothermal gradient. If water percolates deeply enough into the crust, it will be heated as it comes into contact with hot rocks. The water from hot springs in non-volcanic areas is heated in this manner.
In volcanic zones such as Yellowstone National Park, water may be heated by coming into contact with magma (molten rock). The high temperature gradient near magma may cause water to be heated enough that it boils or becomes superheated. If the water becomes so hot that it builds steam pressure and erupts in a jet above the surface of the Earth, it is called a geyser. If the water only reaches the surface in the form of steam, it is called a fumarole. If the water is mixed with mud and clay, it is called a mud pot.
Note that hot springs in volcanic areas are often at or near the boiling point. People have been seriously burned and even killed by accidentally or intentionally entering these springs.
Warm springs are sometimes the result of hot and cold springs mixing but may also occur outside of geothermal areas, such as Warm Springs, Georgia (frequented for its therapeutic effects by paraplegic U.S. President Franklin D. Roosevelt, who built the Little White House there).
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Flow Rates
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Hot springs range in flow rate from the tiniest "seeps" to veritable rivers of hot water. Sometimes there is enough pressure that the water shoots upward in a geyser, or fountain.
A very low flow rate hot spring fed the closed resort, Fales Hot Ditch, which is north of Bridgeport, California. There is a huge subterranean lake below Tonopah, Arizona, which provides natural hot mineral waters to the seven or more hot spring spas that once operated in Tonopah. The ruins of two such spas are still visible in Tonopah.
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High Flow Hot Springs
The Dalhousie Springs complex in Australia had a peak total flow of more than 23,000 liters/second in 1915, giving the average spring in the complex an output of more than 325 liters/second. This has been reduced now to a peak total fow of 17,370 liters/second so the average spring has a peak output of about 250 liters/second.
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Therapeutic uses
Because heated water can hold more dissolved solids, warm and especially hot springs also often have a very high mineral content, containing everything from simple calcium to lithium, and even radium. Because of both the folklore and the proven medical value some of these springs have, they are often popular tourist destinations, and locations for rehabilitation clinics for those with disabilities.
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Infections from Hot Springs
Unfortunately, hot springs can create ideal conditions to spread infections. For example:
the naegleria fowler amoeba lives in warm waters and soils worldwide and can be a cause of meningitis. Several deaths have been attributed to this amoeba, which enters the brain through the nasal passages.
Legionella bacteria have been spread through hot springs.
There is some suggestion that a bather was infected by the herpes simplex virus in his toe from a hot spring in Japan.
There are viruses that have been collected from even very extreme environments in hot springs, like a hot spring with a temperature of 87 to 93°C and an incredibly acidic pH of 1.5 in Pozzuoli, Italy. These viruses were observed to infect cells in the laboratory.
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Hot Springs Parks
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Hot springs around the world
See main article, Hot springs around the world
There are hot springs on all continents and in many countries around the world. Countries that are renowned for their hot springs include Iceland, New Zealand, Chile
and Japan, but there are interesting and unique hot springs in many other places as well:
The town of Spa, Belgium is the origin of the word "spa" and features springs with water temperatures of 32 degrees C. Casanova visited Spa in 1783 looking for business opportunities but was disappointed.
There are more than 275 hot springs registered in Chile.
Ikaria, Greece features a radioactive hot water spring that has been used since the fourth century BCE.
Being located in the "Pacific Ring of Fire", Japan is in a volcanic region, and is home to many hot springs. The onsen (a Japanese word for "hot spring") plays a notable role in Japanese culture. Visiting an onsen is a quintessential Japanese experience and is a popular tourist activity.
Champaign Hot Springs is a shallow submarine geothermal spring system along the coast of the island of Dominica, Lesser Antilles.
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See also
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