Potential Volcanic Hazards
Hidden underground, powerful volcanic, tectonic, and hydrothermal forces are continually reshaping the landscape of Yellowstone National Park. Evidence of these include numerous earthquakes (although not all are felt by humans), uplifting and subsidence of the ground surface. Eventually the unrest will culminate in a large earthquake or volcanic eruption.
A Interfermetric Synthetic Aperture Radar (InSAR)
This InSAR image is able to give a direct and precise measurement of the vertical changes in ground level at Yellowstone National Park in a four year period from 1996-2000. The white dotes here show the locations of earthquakes. Source: http://pubs.usgs.gov/fs/fs100-03/
Evident in the diagram above is the prominent dome-shaped uplifting, this suggests that there is a continuous rise in the caldera from magma reservoirs beneath the earth's surface which has the potential to form a volcano and is also linked to the frequent earthquakes.
Yellowstone Caldera Diagram
The hydrothermal and volcanic activity at Yellowstone Lake are fueled by a large reservoir of magma beneath the caldera that formed 640,000 years ago. Source: http://pubs.usgs.gov/fs/fs100-03/
This diagram shows how the less dense magma from reservoirs deep within the earth move upward and lift the surface of a caldera causing the faults to shift and produce earthquakes.
Seismic Activity at Yellowstone National Park
The Yellowstone area has one of the most seismically active parts in the United States, this graph shows the number of volcanoes in a year and an upward trend in cumulative earthquakes in a span of almost 30 years. Source: http://pubs.usgs.gov/fs/fs100-03/
The largest earthquake recorded to rattle Yellowstone was the Hebgen Lake earthquake in Montana on August 18th, 1959. It had a magnitude of 7.5, killed 28 people and caused damages of $11 million (equivalent to $70 million in 2003).
A landslide broken road Source: www.geo.arizona.edu/ ~cparkjr/hebgen/page3.html
Along with the earthquake threats Yellowstone faces on a daily basis, if ever there was a volcanic eruption the size of those in Yellowstone's history the effects would be devastating for the United States and it would effect the entire world. Such predictions are hard to envision but with the ongoing activity geologists have been observing we can only presume that Yellowstone will erupt once again.
This diagram shows the different hazards that a volcano produces. Source: http.//USGS.org
Volcanologists use two measures of eruption size: the magnitude of the eruption (the volume or mass of magma erupted) and the intensity (the rate of magma eruption). (Magma is the hot, molten, often gas-laden rock material stored under volcanoes.) In principle, these two parameters are independent, but there is good evidence that they are linked. Thus, super-eruptions are not only huge (high magnitude), but also very violent (high intensity).
Eruption of Mount Pinatubo, June 12th, 1991, this eruption is the largest documented with a column of ash and gas rising as much as 20 km into the atmosphere and yet a super-eruption would make this look miniscule. Source: http://encarta.msn.com/.../ Mount_Pinatubo_Eruption.html
A super-eruption has the potential to cover the United States in 3 feet of ash from a plume. Pyroclastic flow would engulf the greater part of three states, and there is evidence that the last major 'super' eruption plunged the world into a freezing, volcanic winter that lasted a decade. An eruption would devastate world agriculture, severely effect the distribution of food and cause mass famine.
This diagram shows the potential range of the total destruction.