Hydrothermal explosion
Encyclopedia
Hydrothermal explosions occur when superheated
water trapped below the surface of the earth rapidly converts from liquid to steam, violently disrupting the confining rock. Boiling water, steam, mud, and rock fragments called breccia
are ejected over an area of a few meters up to several kilometers in diameter. Although the energy inherently comes from a deep igneous
source, this energy is transferred to the surface by circulating meteoric water
rather than by magma
, as occurs in volcanic eruptions
. The energy is stored as heat in hot water and rock within a few hundred feet of the surface.
Hydrothermal explosions are due to the same instability and chain reaction mechanism as geysers but are so violent that rocks and mud are expelled along with water and steam.
increases, causing the water to become superheated
. A sudden reduction in pressure causes a rapid phase transition
from liquid to steam, resulting in an explosion of water and rock debris. During the last Ice Age, many hydrothermal explosions were triggered by the release of pressure as glacier
s receded. Other causes are seismic activity
, erosion
, or hydraulic fracturing
.
is a thermally active area with an extensive system of hot springs, fumarole
s, geysers, mudpot
s, and hydrothermal explosion craters called caldera
. Eight of these craters are in hydrothermally cemented glacial deposits, and two are in Pleistocene
ash-flow tuff
. Each is surrounded by a rim composed of debris derived from the crater, 10 to 30 yards high.
More than 20 large hydrothermal explosions have occurred at Yellowstone, approximately one every 700 years. The temperature of the magma reservoir
below Yellowstone is believed to exceed 800° Celsius causing the heating of rocks in the region. If so, the average heat flow supplied by convection currents is 30 times greater than anywhere in the Rocky Mountains
. Snowmelt
and rainfall seep into the ground at a rapid rate and can conduct enough heat to raise the temperature of ground water to almost boiling.
The phenomena of geyser basins are the product of hot ground water rising close to the surface, and occasionally bubbling through. Water temperatures of 238° Celsius at 332 meters have been recorded at Norris Geyser Basin.
Pocket Basin was originally an ice-dammed lake over a hydrothermal system. Melting ice during the last glacial period caused the lake to rapidly drain, causing a sudden change in pressure triggering a massive hydrothermal explosion.
One well-known hydrothermal geyser is Old Faithful which throws up plumes of steam and water approximately every hour and a half on average. Rarely has any steam explosion violently hurled water and rock thousands of feet above the ground; however in Yellowstone’s geological history these colossal events have been recorded numerous times and have been found to have created new hills and shaped parts of the landscape.
The largest hydrothermal explosion ever documented was located near the northern edge of Yellowstone Lake
, on an embankment commonly known as “Mary Bay”. Now consisting of a mere 1.5 mile crater, it was formed relatively recently, approximately 13,800 years ago. It is believed this crater was formed by a sequence of several hydrothermal explosions in a short time. What triggered this series of events has not been established, but volcanologists
believe a large earthquake could have played a role by accelerating the melting of nearby glaciers. Alternatively, rapid changes in the level of Yellowstone Lake may have been responsible.
and Mammoth Hot Springs). It is estimated that all the hydrothermal craters seen now were created between 14,000 and 3,000 years ago. Volcanologists believe no magma has ever broken through the fragile crust of Yellowstone Park or stirred the movement of magma in the reservoir beneath Yellowstone. These phenomena are now considered to be mutually exclusive events; hydrothermal explosions are not correlated with volcanism
, although throughout the world all hydrothermal systems are heated and caused by magma
.
Superheating
In physics, superheating is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling...
water trapped below the surface of the earth rapidly converts from liquid to steam, violently disrupting the confining rock. Boiling water, steam, mud, and rock fragments called breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
are ejected over an area of a few meters up to several kilometers in diameter. Although the energy inherently comes from a deep igneous
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
source, this energy is transferred to the surface by circulating meteoric water
Meteoric water
Meteoric water is a hydrologic term of long standing for water in the ground which originates from precipitation. This includes water from lakes, rivers, and icemelts, which all originate from precipitation indirectly.- Overview :...
rather than by magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
, as occurs in volcanic eruptions
Types of volcanic eruptions
During a volcanic eruption, lava, tephra , and various gases are expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed...
. The energy is stored as heat in hot water and rock within a few hundred feet of the surface.
Hydrothermal explosions are due to the same instability and chain reaction mechanism as geysers but are so violent that rocks and mud are expelled along with water and steam.
Cause of explosion
Hydrothermal explosions occur where shallow interconnected reservoirs of water at temperatures as high as 250° Celsius underlie thermal fields. Water usually boils at 100°C but under pressure its boiling pointBoiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
increases, causing the water to become superheated
Superheating
In physics, superheating is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling...
. A sudden reduction in pressure causes a rapid phase transition
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....
from liquid to steam, resulting in an explosion of water and rock debris. During the last Ice Age, many hydrothermal explosions were triggered by the release of pressure as glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
s receded. Other causes are seismic activity
Seismic wave
Seismic waves are waves of energy that travel through the earth, and are a result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy. Many other natural and anthropogenic sources create low amplitude waves commonly referred to as ambient vibrations. Seismic waves...
, erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
, or hydraulic fracturing
Hydraulic fracturing
Considerable controversy surrounds the current implementation of hydraulic fracturing technology in the United States. Hydraulic fracturing, or fracking, is the process of utilizing pressurized water, or some other liquid, to fracture rock layers and release petroleum, natural gas, or other...
.
Yellowstone
Yellowstone National ParkYellowstone National Park
Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...
is a thermally active area with an extensive system of hot springs, fumarole
Fumarole
A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...
s, geysers, mudpot
Mudpot
A mudpot, mud pool or paint pot is a sort of hot spring or fumarole consisting of a pool of usually bubbling mud. The mud is generally of white to greyish color, but is sometimes stained with reddish or pink spots from iron compounds...
s, and hydrothermal explosion craters called caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
. Eight of these craters are in hydrothermally cemented glacial deposits, and two are in Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
ash-flow tuff
Tuff
Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...
. Each is surrounded by a rim composed of debris derived from the crater, 10 to 30 yards high.
More than 20 large hydrothermal explosions have occurred at Yellowstone, approximately one every 700 years. The temperature of the magma reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
below Yellowstone is believed to exceed 800° Celsius causing the heating of rocks in the region. If so, the average heat flow supplied by convection currents is 30 times greater than anywhere in the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
. Snowmelt
Snowmelt
In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many parts of the world, in some cases contributing high...
and rainfall seep into the ground at a rapid rate and can conduct enough heat to raise the temperature of ground water to almost boiling.
The phenomena of geyser basins are the product of hot ground water rising close to the surface, and occasionally bubbling through. Water temperatures of 238° Celsius at 332 meters have been recorded at Norris Geyser Basin.
Pocket Basin was originally an ice-dammed lake over a hydrothermal system. Melting ice during the last glacial period caused the lake to rapidly drain, causing a sudden change in pressure triggering a massive hydrothermal explosion.
Geysers
A hydrothermal explosion is similar to a geyser's eruption except that "it blows the lid out" of the surrounding rocks.One well-known hydrothermal geyser is Old Faithful which throws up plumes of steam and water approximately every hour and a half on average. Rarely has any steam explosion violently hurled water and rock thousands of feet above the ground; however in Yellowstone’s geological history these colossal events have been recorded numerous times and have been found to have created new hills and shaped parts of the landscape.
The largest hydrothermal explosion ever documented was located near the northern edge of Yellowstone Lake
Yellowstone Lake
Yellowstone Lake is the largest body of water in Yellowstone National Park, The lake is 7,732 feet above sea level and covers with 110 miles of shoreline. While the average depth of the lake is 139 feet its deepest spot is at least 390 feet...
, on an embankment commonly known as “Mary Bay”. Now consisting of a mere 1.5 mile crater, it was formed relatively recently, approximately 13,800 years ago. It is believed this crater was formed by a sequence of several hydrothermal explosions in a short time. What triggered this series of events has not been established, but volcanologists
Volcanology
Volcanology is the study of volcanoes, lava, magma, and related geological, geophysical and geochemical phenomena. The term volcanology is derived from the Latin word vulcan. Vulcan was the ancient Roman god of fire....
believe a large earthquake could have played a role by accelerating the melting of nearby glaciers. Alternatively, rapid changes in the level of Yellowstone Lake may have been responsible.
Recent explosions
Most of Yellowstone’s recent large hydrothermal explosions have been the consequence of sudden changes of pressure deep within the hydrothermal system. Generally, these larger explosions have created craters in a north-south pattern (between NorrisNorris
- In the United States :* Norris, Illinois* Norris, South Carolina* Norris, Tennessee, named after George William Norris* Norris Dam, which forms Norris Lake, Tennessee* Norris Geyser Basin in Yellowstone National Park* Norristown, Pennsylvania...
and Mammoth Hot Springs). It is estimated that all the hydrothermal craters seen now were created between 14,000 and 3,000 years ago. Volcanologists believe no magma has ever broken through the fragile crust of Yellowstone Park or stirred the movement of magma in the reservoir beneath Yellowstone. These phenomena are now considered to be mutually exclusive events; hydrothermal explosions are not correlated with volcanism
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
, although throughout the world all hydrothermal systems are heated and caused by magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
.
