Yellowstone Volcano's Killer Hazard: Earthquakes

A supervolcano blasting Yellowstone National Park to smithereens may capture the imagination, but the region's real risk comes from earthquakes, researchers reported in Denver on Sunday (Oct. 27) at the Geological Society of America's annual meeting.

"The pervasive hazard in Yellowstone is earthquakes," said Robert Smith, a seismologist at the University of Utah. "They are the killer events."

Smith and his collaborators analyzed 4,520 earthquakes in and around Yellowstone that struck between 1985 and 2013. Their goal: Create the best picture ever of the magma chamber hidden beneath the park's colorful hot springs and spectacular geysers. A side benefit was a better view of the seismic risk from nearby faults. (Infographic: Geology of Yellowstone)

One of these faults triggered the most destructive earthquake ever recorded in the Rocky Mountains - the deadly magnitude-7.3 Hebgen Lake quake in 1959. The epicenter was about 15 miles (24 kilometers) north of West Yellowstone.

Smith said the probability of another magnitude-7 or larger earthquake on one of the major faults near Yellowstone is 0.125 percent. The number reflects the chance an earthquake will occur in any given year, based on past records.

The annual probability of a Yellowstone supereruption is a much smaller 0.00014 percent, Smith said.

Yellowstone National Park is cradled inside a gentle depression created by a giant volcanic eruption 640,000 years ago. The ground collapsed, leaving a bowl-shaped caldera. It was the third in a series of massive eruptions, the first of which exploded 2.1 million years ago.

A mantle plume (also called a hotspot) feeds Yellowstone's supereruptions. Hotspots are massive rising blobs of hot rock from Earth's mantle, the layer beneath the crust. As the planet's tectonic plates trundle over hotspots, the plumes punch through the crust, forming volcanic chains like Hawaii or the Idaho's Snake River Plain and Yellowstone.

In the millennia since the last massive volcanic blowout, magma has again built up beneath Yellowstone. The park trembles constantly with tiny earthquakes as gas and hot fluids course through underground fractures, escaping from the molten rock below.

Led by graduate student Jamie Farrell, the University of Utah group used these tremors like a CT scan, building a precise image of the underground magma reservoir.

However, Yellowstone's magma chamber isn't just a giant pool of molten rock. What's called a partial melt - small interconnected zones of magma filling fractures and small spaces - fills 6 to 7 percent of the crust beneath Yellowstone, Smith said Sunday. "The Yellowstone crustal reservoir is 250 percent larger than previously imaged," Smith said.

The actual volume of molten magma is somewhere between 200 to 600 cubic km (50 to 145 cubic miles), he said.

The reservoir is shaped like a dog's knobby chew toy, with one end about 9 miles (15 km) below the center of Yellowstone National Park, and the other rising to the northeast, about 3 miles (5 km) below the surface.

The shallow end extends 12 miles (20 km) northeast of the caldera rim created 640,000 years ago, Smith said. That distance matches the total tectonic drift of the North American plate over the Yellowstone mantle plume since that time, he said.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.

7 Ways the Earth Changes in the Blink of an Eye Yellowstone and Yosemite: Two of the World's Oldest National Parks Video: Devastating Earthquake Visualized Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Yellowstone is an active volcano. Surface features such as geysers and hot springs are direct results of the region's underlying volcanism.

June 29, 2012:

Predators are both icons and targets. Idealized as symbols of strength and bravery, they are also hunted mercilessly. This duality is exemplified in California's state flag which prominently features the grizzly bear (Ursus arctos horribilis), although the last bear in California was shot in 1922. All is not lost for North America's persecuted predators. Several carnivorous species are beginning to recover slivers of the territory they lost to Western civilization, but as their populations grow, so too do their interactions with humans and livestock. Some of these conflicts and contacts have drawn media attention. This month in Montana, a mother grizzly and her cub had to be relocated after mama bear took down approximately 70 sheep over a two week period. In one night the insatiable ursine mom killed 58 sheep, reported the Great Falls Tribune. In Yellowstone, America's most famous population of grizzlies may have reached the maximum the park can support. The population in the core area of Yellowstone grew by four to seven percent from the 1980s to the early 2000s, but has leveled off at around 600 for the past few years, reported the Wyoming Star-Tribune. But the bears may not be welcome outside of the park. "The bears in the Yellowstone area are filling up their logical habitat," Steve Schmidt of the Idaho Fish and Game Department said in the Missoulian. "We also believe as a committee that bears have met or exceeded their social carrying capacity. The public appetite for further expanding this bear population is very small. And the political appetite is nil." Grizzlies once ranged from the Arctic as far south as Mexico and roamed the Great Plains, but by the mid-20th century they had been reduced to only Canada and Alaska with a tiny remnant population in the lower 48 states. Yellowstone National Park is now the furthest south that the bears live.

Gray Wolves

Like the grizzly bear, wolves once ranged over most of North America. Gray wolves (Canis lupus) were Earth's widest ranging land mammal until the rise of Homo sapiens. By the 1950s, the wolf had nearly disappeared from most of the lower 48 states of the U.S., though populations remained strong in northern Canada and Alaska. In 1995, Canadian wolves were captured and reintroduced into Yellowstone National Park in northwest Wyoming. The wolves thrived in the park. The return of the wolf packs balanced the area's ecosystem because the howling hunters chowed down on the overpopulated elk that were devouring too much vegetation. All those tasty elk did the trick and the wolf population grew from a founding group of 68 in 1995 to 98 at the end of 2011, according to the National Park Service. In other parts of the increasingly wild West, wolves rebounded as well. Now, approximately 1,774 wolves roam Idaho, Montana and Wyoming. The predatory packs had been protected until last year, when Congress ordered the wolves removed from the Endangered Species List. Although this caused outrage, a group of wolf advocates decided not to appeal the case to the Supreme Court earlier this month, according to the Seattle Post Intelligencer. Other wolf species face fiercer foes than legislators. Two packs of highly endangered Mexican gray wolves are threatened by the intense wildfire raging in New Mexico, reported the Christian Science Monitor. The species was extinct in the wild until captive bred wolves were released in New Mexico and Arizona in 1998. There are now approximately 50 wild wolves roaming the Southwest.

Cougar

Pumas -- also known as cougars, mountain lions, and panthers -- once prowled from central Canada to the tip of Argentina and from the Atlantic to the Pacific. The big cats still prowl much of their range, but were exterminated in most parts of North America east of the Rocky Mountains. Where the cats still live, attacks are rare but brutal. An estimated 4,000 to 6,000 cougars live in California, but since 1890 there have been only six fatal attacks, according to the San Francisco Chronicle. The last fatal attack in the U.S. was in New Mexico in 2008. The low probability of a fatal attack doesn't reduce the fear Midwesterners may feel now that mountain lions are returning to the region. A recent study in the Journal of Wildlife Management documented the cougar comeback. Between 1990 and 2008, there were 178 confirmed cougar sightings in Midwestern regions where the cats had previous been mostly eradicated. The pumas pounced on Nebraska the hardest, with 67 sightings, reported the Omaha World-Herald. Some cats made it as far as Connecticut, 1,500 miles away. So far most of the meandering mountain lions are believed to be restless males wandering hundreds of miles in search of mates. If females start to spread as well, the cats could return anywhere there is enough prey, such as deer. Perhaps nature will soon provide the solution to the suburban deer that regularly devour homeowners' gardens and landscaping.

Black bears

Of all the large carnivores making a comeback, the black bear (Ursus americanus) is the most likely to be found napping in the basement waiting for the TV repairman. A baby bear might even be hanging around the garage until mama bear comes along to let it out. If a bear gets bored of chilling out in suburbia, it can always hitch a ride downtown. Black bears once lived in most forested areas of North America, but the bears' territory shrank as cities and farms expanded. But this bear isn't rare. There may be as many as one million black bears, mostly in the U.S. and Canada. Beware of the bear! Although not as territorial and defensive as its massive cousin the grizzly, black bear attack are on the rise as humans push further into the bears' domain. Wild bears killed 63 people over the past 110 years, according to a study in the Journal of Wildlife Management, and the rate has been increasing since the 1960s. Recently, three bears were shot in Arizona after a string of attacks, reported the Payson Roundup. Officials believe the bears may have resorted to raiding human habitations because the animals were having a hard time finding food due to the drought in the region.

Rattlesnakes

Not all deadly predators are huge beasts. Some hide beneath piles of leaves, or look like a stick in a Wal-Mart garden center. This year an above average number of venomous fangs have been sinking into human flesh. The warm winter leading into an early spring made 2012 perfect for cold-blooded creatures. California's snakebite tally for April and May, 129, is nearly double last years' count of 70. In Texas, two undocumented immigrants from Guatemala were bitten by rattlesnakes. Border patrol agents found them and took them to a hospital where they are expected to recover, reported Valley Central. Besides being caught and deported, those men were lucky. Untreated snake bites can be deadly, like the recent death of a snake-handling Pentecostal preacher bitten by one of his serpents. On the whole, humans aren't usually in harms way of these predators. Snake bites kill an average of 6 people per year in the U.S., according to the University of Florida. An American is nine times more likely to die from a lightning strike than a rattlesnake's strike. On the other hand, some people make a sport of slaughtering serpents. In Sweetwater, Texas, the annual Rattlesnake Round-up draws upwards of 30,000 spectators calling out for cold-blood. In 2003, hunters brought in 4,207 pounds of rattlesnakes to be put on display then massacred. Several other cities, such as Opp, Georgia, have round-ups as well. Conservationists have protested such events, stating that eastern diamondback rattlesnake (Crotalus adamanteus) numbers are declining and that the way they are treated is animal abuse, reported the AP.

Bald Eagle

The rattlesnake was once a symbol of the United States, warning enemies, "Don't tread on me." Another symbol of the States, the bald eagle, had some hard times, but is now back on the branches of America's forests. The eagle plunged from a population in the hundreds of thousands in the 18th century down to only 412 nesting pairs in the lower 48 during the 1950s, though populations in the far north remained strong. Thousands of eagles were shot. Thousands more were unable to reproduce after the insecticide DDT made their eggs too brittle to survive. Strict enforcement of hunting bans and outlawing DDT saved the eagles from disappearing from the land they represent. Once conditions improved, the eagles made a comeback. June 28th was the fifth anniversary of the eagle's removal from the from the Endangered Species list. The species' population is now estimated at more than 100,000. Today's go-getter eagles can even handle the hustle of city life. More than a dozen bald eagle nests can be found within the Chicago metropolitan area, reported the AP. Some bald eagles still need a hand from humans. In May, two bald eagle chicks fell from their nest near Boston, Massachusetts and were taken to a wildlife rehabilitation center. One day before the anniversary of their species' removal from the endangered species list, the birds were set free, reported CBS News Boston.

Coyote

Some predators never had anything to worry about when Western civilization started encroaching on their domain. Coyotes may have suffered somewhat from bullets and traps, but they benefited from having their main rival and threat, the wolf, taken out of the picture by humans. Coyotes were once limited to western North America from Alaska to Panama, but now live virtually everywhere in North America. Coyotes have adapted to the suburbs and can even become city-dwellers. An Ohio State University study estimated that 7,000 wolves live in the metropolitan Chicago area. One consequence of living close to humans is the tendency of coyotes to mate with domestic dogs. The “coydog” offspring have the coyote's wild instincts, but lack their fear of humans. Coyotes don't play coy with wolves either. Many of the canids in New England and eastern Canada may be descendants of hybrid coywolves. The group has formed its own distinct population, called eastern coyotes. A Canadian folk singer, Taylor "Mitchell" Luciow, was killed by coyotes that wildlife managers suggest may have been this larger more aggressive eastern breed, reported National Geographic. Luciow' s death was the first and only known killing of an adult human by coyotes. A recent string of three attacks on humans by coyotes was out of character for the normally shy pure-breed coyotes. The attacks all occurred within a 10 day period. Two attacks injured women in California, reported ABC News. Then a 5-year-old girl was jumped upon and nipped by a coyote in Oregon, but received only scratches. Officials believe that the drought prevailing over much of the U.S. may have made the coyotes agitated and sent them searching for food and water in unfamiliar territory.