Hidden almost 5 miles beneath the spectacular mountains of Yellowstone National Park lies a slumbering giant beast. Approximately 34 x 45 miles in size, the Yellowstone caldera, also known as the Yellowstone super volcano, rocks, rolls and rumbles on a daily basis. Under incredible pressure, the “Yellowstone Hotspot” is a massive chamber of molten rock, a pulsating magma powering Yellowstone’s impressive mud pits, fumaroles, hot springs and the world’s largest collection of geysers.
The oldest park in the United States National Park System, Yellowstone National Park was established in 1872 as America’s first national park. Straddling the Montana and Wyoming border with the majority of the park in Wyoming, Yellowstone is unlike any other spot on the planet. Jaw-dropping scenery, crystal clear sapphire skies, majestic mountains and a diversity of wildlife attract visitors from every corner of the world. A wild mountainous land, home to wolves, grizzly bear, cougar, elk, moose, deer, antelope, bison and a diverse array of small wildlife and fowl, Yellowstone National Park is one of the very few remaining natural ecosystems on the planet.
Without a doubt, the diverse hydrothermal features of the park are its most enticing fascination and “must-see” tourist attraction. There is no other location anywhere in the world that presents as many steam vents, active geysers and hot spring as found within Yellowstone National Park.
Although considered by many to be one of the most beautiful spots on earth, don’t let the awe-inspiring scenery deceive. Yellowstone has a violent and volatile geologic history. The park rests atop numerous shifting layers of ash deposits with an explosive volcanic past. 640,000 years ago, the Lava Creek explosion (the last in a long chain of full-scale eruptions) ejected more than 240 cubic miles of ash, dust and rock into the heavens.
The most devastating earthquake in recent history occurred on August 17th, 1959. Centered near Hebgen Lake, Montana the region was blasted with a magnitude 7.1 quake that triggered giant landslides that killed 28 people and cause in excess of $11 million dollars in property damage. Active geysers in the Park mysteriously changed eruption times. New geysers formed and began to erupt. After the 1959 earthquake, the giant slumbered until Yellowstone awakened again on June 30,1975 with a magnitude 6.4 tremor that shook the valley.
Subsequent manifestations of earthquake activity recorded by seismographs in the Yellowstone region demand the attention of geologists, search and rescue teams, emergency medical personnel and laymen alike.
Yellowstone.net advises, “Even distant earthquakes can affect Yellowstone. In November 2002, the magnitude 7.9 Denali Fault earthquakes struck central Alaska, 1,250 miles (2,000 km) northwest of Yellowstone. Because this quake’s energy was focused toward the active Yellowstone volcanic and hydrothermal system, it triggered hundreds of small earthquakes there. The region’s hydrothermal system is highly sensitive to quakes and undergoes significant changes in their wake. Earthquakes may have the potential to cause Yellowstone’s hot-water system to destabilize and produce explosive hydrothermal eruptions.”
The Yellowstone Volcano Observatory, a cooperative effort of the National Park Service, the U.S. Geological Survey, and the University of Utah, the state geological survey from Idaho, Montana and Wyoming and the University of Wyoming, reports more than 500 separate quakes recorded by seismographic equipment between December 27th, 2008 and January 5th, 2009. Known by geologists and scientists as an “earthquake swarm”, activity centered around the active volcano.
Scientists tell us earthquakes in close proximity to an active volcano are considered fairly common. Typically seismographs positioned around Yellowstone National Park record 1,000 to 3,000 earthquakes each and every year. What caused great concern in 2008-2009 was that the “swarm” of 500 earthquakes occurred in less than a week. The activity renewed the focus of the scientific community and emergency preparation organizations when the Yellowstone Volcano Observatory declared the earthquake swarm “the most intense in this area for some years and is centered on the east side of the Yellowstone caldera.”
The strongest 2008-2009 earthquake recorded was a magnitude 3.9 at the onset of the swarm. The strong quake and numerous aftershocks jolted park rangers, visitors and local residents. Geologists calculated from seismic data that the 2008-2009 quakes occurred at depths ranging from 1 to about 10 miles beneath the surface. The quakes were attributed to rising magma and the subsequent heating and breaking of rocks as the earth shifted.
Due to its unique location within a 40-mile wide ancient caldera, Yellowstone National Park earns the unique distinction of being the location with the world’s largest concentration of active geysers.
Standing like sentinels to the Gates of Hades, hydrothermal vents present travertine, geyserite or sinter deposits built-up around and within them. Sending up wisps of steam that seem to dance in the moonlight, the vents are both mystical and haunting.
The type of geothermal activity found in Yellowstone National Park requires two main ingredients: intense heat and an abundance of water. Yellowstone provides both large quantities.
Geyser basins are found in areas where melting snow and rain can readily percolate into the ground, become indirectly superheated by the underlying Yellowstone hotspot. The pent-up thermal energy then erupts at the surface as fumaroles, hot springs and powerful geysers. Much of the geothermal areas are located in narrow valleys tucked between the glacial moraines and ancient lava flows.
A few geothermal areas are located where fault lines reach the surface near the fracture zone of the giant caldera and at the bottom of steep slopes that contain and drain excess snow melt and groundwater.
Bob Christiansen, the USGS scientist who delineated the three Yellowstone calderas commented about the great eruptions that formed them. Christensen reported “he traced out the caldera boundaries through old fashioned field work… walking around with a hammer and hand lens and looking carefully at the rocks and their distributions”. Most of the key observations were recorded in the 1960s and 1970s.
Because of the high elevation of the Yellowstone Plateau, boiling temperature at Yellowstone’s geyser basins is 199 °F (93 °C). Confined and close to the earth’s surface, periodic releases of built-up pressure create violent eruptions of steam and heated mineral-rich waters that can reach up to 390 feet (120 m) into the air. The water erupting from Yellowstone’s impressive geysers is superheated above that boiling point to an average of 204 °F (95.5 °C) when it leaves the vent. Steamboat Geyser, located within Yellowstone National Park is the world’s tallest geyser.
Water from the geysers cool while airborne and are no longer scalding hot by the time they strikes the ground. However, as a safety precaution, visitors are strongly warned that because of the high temperatures of the water, it is critical that spectators remain on the boardwalks and designated trails. Numerous deaths have occurred in the park as a result of slips and falls into geysers, hot springs and mud holes.
The first prehistoric people that inhabited the area lived in awe and fear of the 10,000 geothermal features and 200 – 250 geyser eruptions annually in and around the area now known as Yellowstone National Park. Ancient artifacts indicate that these first people used the pools for healing, bathing and cooking. For these first tribal people, the life-giving waters held a special spiritual significance.
During the 19th Century, Father Pierre-Jean De Smet reported that native people he talked to believed the terrifying geyser eruptions were “the result of combat between the infernal spirits.”
In 1806, the Lewis and Clark Expedition trekked to the northern rim of the caldera. Local Indian tribes told tales of a mysterious valley of spirits where the earth trembled and roared like thunder; the frightening loud noises proclaiming the land demonically possessed and visitors unwelcome. Afraid and respectful, the Indians rarely dared to go near the fearsome cauldrons.
History notes, John Colter, an adventurous explorer who had left the Lewis and Clark Expedition, as the first known white man to venture into the caldera and see the incredible geothermal events. Colter described what he saw as “hot brimstone.” In the early 1850s, the famous trapper and trekker, Jim Bridger called it “the place where Hell bubbled up.”
Seismic data from 2004 through 2008 indicates that the land surface within the giant Yellowstone caldera shifted upwards, as much as 8 inches at the White Lake GPS station. The caldera floor has risen 3 inches per year for several years. This rate-of-rise is considered more than three times greater than ever observed since such geologic measurements commenced in 1923. As of January 2010, the shifting had slowed considerably.
While earthquake swarms, similar to the 2008-2009 activity, have occurred in the past in Yellowstone without triggering volcanic activity or steam explosions, the threat remains. Concern mounted when 1620 small earthquakes occurred between January 17, 2010 and February 1, 2010. This flurry of activity was the second largest ever recorded at the Yellowstone Caldera. The strongest shock then to date was a 3.8 tremor recorded on January 21, 2010. The 2010 rumblings are well remembered by the folks of the villages of Old Faithful, West Yellowstone, Canyon, Mammoth Hot Springs, Grant Village, Madison, and Gardiner.
The University of Utah Seismograph Stations reported an earthquake of magnitude 3.7 occurred on September 05, 2012. The epicenter of the shock was located in Yellowstone National Park, 12 miles NE of the town of West Yellowstone, Montana. Participating seismograph stations notes a total of 49 earthquakes of magnitude 3.0 or greater have occurred within 16 miles of the epicenter of this event since 1962. The largest of these events was a magnitude 4.2 on November 23, 2000, 2 miles NNW of Norris Junction, Wyoming. The Yellowstone Plateau averages about 1,600 earthquakes a year. Strong potential for hydrothermal explosions and major earthquakes continue.
Currently, scientists and geologists closely monitor fluctuating magna pressure in the Yellowstone Plateau. Yellowstone Volcano Observatory continues to analyze seismic and ground deformation data: endeavoring to evaluate and understand any changes to the thermal masses located near the epicenters. Continuous volcanic activity is evidenced at numerous vents throughout the region, Including famous Old Faithful Geyser.
Mike Stickney, director of earthquake studies at the Montana Bureau of Mines and Geology, said there is no way to predict when the next big one will hit. Stickney stated it will likely occur along one of the 45 faults that line two belts – one stretching from Yellowstone National Park up to Helena, Montana, and a second one along the Montana-Idaho border.
By: Marlene Affeld
Recent Earthquake Activity In The Intermountain West
United States Geological Survey
National Park Service