Volcanic Hazards
A number of hazards are possible in the Yellowstone region, some being more likely than others from research of previous volcanic patterns and return periods.
Earthquakes
Earthquakes in the Yellowstone area are a likely hazard they are caused from rising magma and hot-ground-water movement, and more significantly due to Basin and Range extension of the western U.S. This is predominantly notable along the Teton and Hebgen Lake Faults (USGS, 2012).
Hydrothermal Explosion
One of the most likely types of eruptions would be of hydrothermal nature, not volcanic. Hydrothermal explosions occur when hot ground waters flash to steam, this violently fractures the confining surrounding rocks (USGS, 2007). Although small, the shallow reservoirs of steam or hot water can launch large rocks from the source of hydrothermal eruption. At Excelsior Geyser in the Midway Geyser Basin, a succession of powerful hydrothermal explosions and geyser eruptions occurred in the 1880’s and early 1890’s. Some of the explosions sent large rocks as far as 15 meters (USGS, 2012). The longevity of these eruptions varies from a few seconds or up to several hours, and explosive activity can occur intermittently for several years (USGS, 2007). Christiansen et al. (2007) discuss that hazards from hydrothermal explosions can affect areas 5-20 times the size of the crater, with rocks being blasted up to 2km from the crater source.Average recurrence of 2 years for small eruptions to 200 years for large eruptions forming craters of >100m (Christiansen et al. 2007).
Lava Flow
Another very likely type of volcanic eruption would extrude lava flows of either rhyolite or basalt. These would be substantial and flows could exceed volumes of 1 km3 (USGS, 2012), the largest recorded basaltic eruption extruded 20 km3 of flood basalt from at least two vents covering approximately 900 square km (Christiansen, et al. 2007). The second largest flood basalt recorded covered an area of approximately 100 square km erupting from 13 vents (Christiansen, et al. 2007). Based on vent and lava flow locations the most likely location for a future basaltic eruption is within the SW end of Island Park Basin however basaltic eruptions could occur anywhere within a band about 40 km wide surrounding the Yellowstone caldera. These basaltic outpourings could possibly flow for up to several months reaching thicknesses tens of meters thick (Christiansen et al. 2007).
There is evidence of at least 17 large rhyolitic lava flows in the Yellowstone Caldera area, the largest of which covered an area > 350 square km at volumes > 30 cubic km.
An average recurrence of 16,000 years for basaltic eruptions and an average recurrence of 20,000 years for rhyolitic eruptions (Christiansen et al. 2007).
Caldera Forming Eruption
The worst-case scenario and least likely volcanic eruption at Yellowstone would be an explosive caldera- forming “super volcano” eruption, three cataclysmic eruptions of this size occurred 2.1 million, 1.3 million, and 640,000 years ago. An eruption of this magnitude would produce extremely large ash columns that exceed 10 km and could reach as high as 50 km covering much of the United States with some ash. These ash particles can enter the stratosphere and encircle the globe, this in combination with SO2 released during eruption can affect global temperatures with many devastating follow on effects (USGS, 2012).An estimated annual probability of > 10^-6 (Christiansen et al. 2007)
Pyroclastic Flows
In association with a caldera forming eruption, are massive pyroclastic flows. These hot (often exceeding 800°C), chaotic mixtures of rock fragments, gas, and ash have the ability to travel rapidly (tens of meters per second) away from a volcanic vent or collapsing flow front, destroying everything in their path (USGS, 2012).
Earthquakes
Earthquakes in the Yellowstone area are a likely hazard they are caused from rising magma and hot-ground-water movement, and more significantly due to Basin and Range extension of the western U.S. This is predominantly notable along the Teton and Hebgen Lake Faults (USGS, 2012).
Hydrothermal Explosion
One of the most likely types of eruptions would be of hydrothermal nature, not volcanic. Hydrothermal explosions occur when hot ground waters flash to steam, this violently fractures the confining surrounding rocks (USGS, 2007). Although small, the shallow reservoirs of steam or hot water can launch large rocks from the source of hydrothermal eruption. At Excelsior Geyser in the Midway Geyser Basin, a succession of powerful hydrothermal explosions and geyser eruptions occurred in the 1880’s and early 1890’s. Some of the explosions sent large rocks as far as 15 meters (USGS, 2012). The longevity of these eruptions varies from a few seconds or up to several hours, and explosive activity can occur intermittently for several years (USGS, 2007). Christiansen et al. (2007) discuss that hazards from hydrothermal explosions can affect areas 5-20 times the size of the crater, with rocks being blasted up to 2km from the crater source.Average recurrence of 2 years for small eruptions to 200 years for large eruptions forming craters of >100m (Christiansen et al. 2007).
Lava Flow
Another very likely type of volcanic eruption would extrude lava flows of either rhyolite or basalt. These would be substantial and flows could exceed volumes of 1 km3 (USGS, 2012), the largest recorded basaltic eruption extruded 20 km3 of flood basalt from at least two vents covering approximately 900 square km (Christiansen, et al. 2007). The second largest flood basalt recorded covered an area of approximately 100 square km erupting from 13 vents (Christiansen, et al. 2007). Based on vent and lava flow locations the most likely location for a future basaltic eruption is within the SW end of Island Park Basin however basaltic eruptions could occur anywhere within a band about 40 km wide surrounding the Yellowstone caldera. These basaltic outpourings could possibly flow for up to several months reaching thicknesses tens of meters thick (Christiansen et al. 2007).
There is evidence of at least 17 large rhyolitic lava flows in the Yellowstone Caldera area, the largest of which covered an area > 350 square km at volumes > 30 cubic km.
An average recurrence of 16,000 years for basaltic eruptions and an average recurrence of 20,000 years for rhyolitic eruptions (Christiansen et al. 2007).
Caldera Forming Eruption
The worst-case scenario and least likely volcanic eruption at Yellowstone would be an explosive caldera- forming “super volcano” eruption, three cataclysmic eruptions of this size occurred 2.1 million, 1.3 million, and 640,000 years ago. An eruption of this magnitude would produce extremely large ash columns that exceed 10 km and could reach as high as 50 km covering much of the United States with some ash. These ash particles can enter the stratosphere and encircle the globe, this in combination with SO2 released during eruption can affect global temperatures with many devastating follow on effects (USGS, 2012).An estimated annual probability of > 10^-6 (Christiansen et al. 2007)
Pyroclastic Flows
In association with a caldera forming eruption, are massive pyroclastic flows. These hot (often exceeding 800°C), chaotic mixtures of rock fragments, gas, and ash have the ability to travel rapidly (tens of meters per second) away from a volcanic vent or collapsing flow front, destroying everything in their path (USGS, 2012).
Old Faithful Geyser, Yellowstone National Park. A hydrothermal explosion is similar to a geyser, except it blasts the enclosing rock apart.
Rhyolitic A'a lava flow, higher viscosity than basaltic composition, producing a thicker, slower flow.
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Basaltic lava flow, low viscosity allows the lava to flow easily, covering a large area.
Interpretation of a Yellowstone caldera forming eruption, displaying large volumes of ash and explosive material ejected into the atmosphere from multiple volcanic vents and large pyroclastic density currents flowing from the base of the eruptive columns.
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Hazards documented in this report
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Hazards not documented in this report
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History
Over the last 2.1 million years the Yellowstone region has evolved through 3 cycles of large inundations of rhyolite lava and volcanic ash, each of them experiencing extremely large pyroclastic-flow eruptions; the rapid extrusion of such enormous volumes of material causing collapse of a central area to form large calderas. Other eruptions have discharged basaltic lava flows around the boundaries of the volcanic field (USGS, 2012).
The area is also known to experience significant earthquakes just off the plateau along the Teton and Hebgen Lake faults; A M7.5 earthquake was experience due to rupture of the Hebgen Lake fault in 1959, causing considerable damage to the region (USGS, 2012).
The area is also known to experience significant earthquakes just off the plateau along the Teton and Hebgen Lake faults; A M7.5 earthquake was experience due to rupture of the Hebgen Lake fault in 1959, causing considerable damage to the region (USGS, 2012).
Potential Effects
Ash fall (deposit)
Roof collapse in built-up areas – a local effect out to distances where ash fall is a few centimetres
thick (tens of kilometres from the volcano). Exacerbated if rain occurs or ash fall is wet.
Agriculture – devastation and disruption for at least a growing season over most of the area
receiving ash fallout. Longer-term changes to soil composition.
Drinking water – potential for both chemical and filtration/blockage problems associated with water
supply.
Aviation – risk to flying aircraft while ash still airborne (days to weeks); problems with landing and
take-off until airports cleared.
Power generation – effects of ash on hydroelectric and nuclear power plants unknown.
Power distribution – electric pylons and power lines might be susceptible to ash loading and
associated electrostatic effects. Possibly exacerbated if ash fall is wet.
Health (see Gas and aerosols)
Pyroclastic flows and deposits
Burial - all objects on ground and fires on a local scale, up to perhaps 50–80 kilometres from
source volcano.
Destruction - complete destruction of infrastructure in the path of a pyroclastic flow
Gas and aerosols
Climate change – dominantly lower temperatures for a few years after the eruption might change
agricultural yields. Some areas may undergo warming, and there might be short-term, very warm
spells that could also affect growing crops. Changes in rainfall patterns may influence liablilty to
flooding in certain areas.
Dry-fog and acid aerosol air pollution – a Laki-type dry fog in the lower atmosphere (composed
of sulphur dioxide gas and sulphuric acid aerosols) could induce respiratory illness, as could
fine ash (< 10 microns) and other minerals in the ash. Such clouds can attain complete coverage
within a hemisphere. Chemical etching effects of aerosol particles on aircraft engines and
instrumentation is a little understood aspect.
Ozone depletion – stratospheric aerosols will serve to catalyse ozone loss, permitting more UV-B
flux to the ground in high–mid latitude regions, the effect lasting a few years after the eruption.
General
Disruption of national and international relief efforts and cooperation.
Disruption of some communications (satellites may not be able to recieve or transmit information
normally due to ash and/or aerosols in the lower atmosphere.
Possible effects of all the above on world financial markets.
Roof collapse in built-up areas – a local effect out to distances where ash fall is a few centimetres
thick (tens of kilometres from the volcano). Exacerbated if rain occurs or ash fall is wet.
Agriculture – devastation and disruption for at least a growing season over most of the area
receiving ash fallout. Longer-term changes to soil composition.
Drinking water – potential for both chemical and filtration/blockage problems associated with water
supply.
Aviation – risk to flying aircraft while ash still airborne (days to weeks); problems with landing and
take-off until airports cleared.
Power generation – effects of ash on hydroelectric and nuclear power plants unknown.
Power distribution – electric pylons and power lines might be susceptible to ash loading and
associated electrostatic effects. Possibly exacerbated if ash fall is wet.
Health (see Gas and aerosols)
Pyroclastic flows and deposits
Burial - all objects on ground and fires on a local scale, up to perhaps 50–80 kilometres from
source volcano.
Destruction - complete destruction of infrastructure in the path of a pyroclastic flow
Gas and aerosols
Climate change – dominantly lower temperatures for a few years after the eruption might change
agricultural yields. Some areas may undergo warming, and there might be short-term, very warm
spells that could also affect growing crops. Changes in rainfall patterns may influence liablilty to
flooding in certain areas.
Dry-fog and acid aerosol air pollution – a Laki-type dry fog in the lower atmosphere (composed
of sulphur dioxide gas and sulphuric acid aerosols) could induce respiratory illness, as could
fine ash (< 10 microns) and other minerals in the ash. Such clouds can attain complete coverage
within a hemisphere. Chemical etching effects of aerosol particles on aircraft engines and
instrumentation is a little understood aspect.
Ozone depletion – stratospheric aerosols will serve to catalyse ozone loss, permitting more UV-B
flux to the ground in high–mid latitude regions, the effect lasting a few years after the eruption.
General
Disruption of national and international relief efforts and cooperation.
Disruption of some communications (satellites may not be able to recieve or transmit information
normally due to ash and/or aerosols in the lower atmosphere.
Possible effects of all the above on world financial markets.