Dear Friends,
http://www.earthfiles.com/news.php?ID=1674&category=Science
David
Yellowstone Seismic Swarms - What Do They Mean?
January to February 2010 seismic swarm largest since 1985.
© 2010 by Linda Moulton Howe
“640,000 years ago it's estimated that 240 cubic miles blasted
out of the Yellowstone caldera ...enough material to bury the state of Texas
beneath about 5 feet of debris” - Jacob Lowenstern, Ph.D., USGS Geologist
on the northwestern part of the Yellowstone caldera (red dots on map). By February 8, 2010,
there had been about 1,800 earthquakes – most of them too small to be felt, but some were larger and
people felt them around the Old Faithful geyser. Map by Univ. of Utah Seismology Research Group.
Old Faithful is a cone geyser located in Wyoming's Yellowstone National Park.
The geyser erupts with a frequency that can range between 45 to 125 minutes,
for 1.5 to 5 minutes and can erupt as high as 106 to 185 feet. Image by USGS.
- At 1 PM on January 17, 2010, a swarm of small earthquakes began shaking the ground around Old Faithful in Yellowstone Park. Over the next three weeks until February 8, 2010, there would be nearly 2,000 quakes on the northwestern edge of the Yellowstone Caldera that was created 645,000 years ago when there was a gigantic magma explosion that blasted 240 cubic miles into the atmosphere, enough material to bury the state of Texas beneath 5 feet of ash and debris.
The January to February 2010 Yellowstone seismic swarm is the largest since 1985. None of the quakes were above 3.8 magnitude on the Richter scale, but since the swarm was felt throughout the park and in Wyoming, Montana and Idaho, people began asking: could Yellowstone Park be building up to another big volcanic eruption?
I took that question to the Scientist-In-Charge at the Yellowstone Volcano Observatory in his U. S. Geological Survey office in Menlo Park, California. Jacob Lowenstern received his Ph.D. in Geology from Stanford University in 1992 and has been assigned to Yellowstone since the volcano observatory began in 2002.
The 2010 seismic swarm of earthquakes began on January 17, 2010,
around 1:00 PM MST about 10 miles (16 km) northwest of the Old Faithful
area on the northwestern edge of the Yellowstone Caldera. By February 8, 2010,
there had been about 2,000 earthquakes reaching 3.8 magnitude – a very intense
seismic swarm, the largest since 1985. The above helicorder is seismic data from
January 17 - February 8, 2010, recorded by the seismometer in borehole B207, about
7 miles (12 km) northeast of the 2010 swarm. Source: Plate Boundary Observatory.
Interview:
Jacob Lowenstern. Ph.D., Research Geologist (volcanologist), U. S. Geological Survey (USGS) and Scientist-In-Charge, Yellowstone Volcano Observatory (YVO), Menlo Park, California: “These swarms are something that happens pretty frequently at Yellowstone – they are not all as big as this particular seismic swarm was. This was the second largest swarm that we’ve seen over the last 30 years, but it’s something that does happen. It’s a very active system. There’s magma, molten rock, beneath the ground at several miles depth and there’s a boiling ground water system that causes the geysers in Yellowstone and the hot springs. It’s a very active place and we get earthquakes there.
The largest seismic swarm was in 1985. It lasted a couple of months and had over 3,000 earthquakes – some of them approaching Richter magnitude 5 – a very intense event and larger than this one in 2010.
BUT THIS 2010 IS LARGEST SINCE 1985?
Yes, that’s correct.
THAT’S WHY I THINK THE GENERAL PUBLIC IS CONCERNED ABOUT – COULD THE YELLOWSTONE CALDERA BLOW UP AGAIN WITH MAGMA?
In terms of swarms, one also has to realize that the last time a volcanic eruption happened at Yellowstone was about 70,000 years ago, and swarms like this (2010) and larger have probably been happening on a decadal level every 10 or 20 years for thousands and thousands of years. We certainly have evidence that the place has been active for a long, long time. So, clearly these kinds of earthquake swarms can occur without volcanic eruptions ever happening.
Could 2010 Seismic Swarm
Lead to Magma Eruption?
HOW DO YOU KNOW THAT THE JANUARY TO FEBRUARY 2010 SWARMS ARE NOT LEADING UP TO SOME KIND OF MAGMA ERUPTION?
What we know is that these seismic swarms happen frequently and we aren’t seeing any other sorts of events that are going on that we think might be happening prior to a volcanic eruption. For example, most eruptions when they happen, the magma starts rising and the ground swells a significant amount. At Yellowstone, we might expect on the order of several feet of swelling prior to a magma eruption. We’d also expect that we would start getting some steam explosions occurring as magma started getting closer to the ground water system and started perturbing it.
So, we would look for a combination of these swarms plus explosions plus ground deformations. When we start to see all those things happening, or even more than one happening at the same time, then we’ll definitely think it is somewhat more likely that a volcanic eruption could ensue.
But if we’re only seeing earthquakes in a very localized area and they are relatively small, we know that is something that happens quite frequently and there is no reason to expect anything more at that point.
Yellowstone's Growing Bulge
BUT ISN’T IT TRUE THAT OVER THE PAST SEVERAL YEARS THERE HAS BEEN A GROWING BULGE IN THE YELLOWSTONE PARK AREA?
Yeah, Yellowstone has been rising over time. The Yellowstone caldera itself has risen about 25 centimeters (10 inches) at a maximum, so that’s on the order of 10 inches of growth over the caldera. That’s something again we have seen over time. Between the 1920s and 1970s, there was an 80-centimeters-rise, or about three times that more recent level of uplift.
Seismic Swarms Release Pressure On Magma
What appears to happen is that the seismic swarms help relieve the pressure that has accumulated during the period of uplift. So, in a way what might be happening is that the pressure builds up a bit, the ground is rising and then earthquakes are one way that Nature relieves the pressure. Then in the case of the rise from the 1920s to 1970s, the big swarm in 1985 was associated with the beginning of subsidence or falling of the caldera. So, the current thought is that the earthquakes (seismic swarms) are related to that pressure release.
And so in this particular case (rising caldera), we had uplift from around 2006 to the present (2010) and it’s been slowing. We had a pretty big swarm about a year ago. We’re now seeing another swarm and many of us are suspecting that we’re going to start to see subsidence of the caldera in the future.
The Grand Geyser is the tallest of the predictable Yellowstone geysers in the park.
Grand's fountain erupts every 7–15 hours and reaches a height of as much as
200 feet (60 m), for as long as 9 to 12 minutes. Image by Mbz1.
DO YOU SEE THE SEISMIC SWARMS AND GEYSERS ALONG WITH THE SEISMIC SWARMS AS A RELEASE OF GASES AND HOT WATERS THAT HELP TO KEEP THE MAGMA FROM EXPLODING?
Yes, the geyser system at Yellowstone is Nature’s release system for the magma down below. We have an enormous body of magma. It’s cooling, it’s crystallizing. Gas is passing through it and the geyser system is one way and earthquakes are another way that the pressure is relieved off of that system.
SO A SWARM OF SEISMIC EVENTS AT YELLOWSTONE PARK SHOULD NOT NECESSARILY MAKE PEOPLE NERVOUS. THEY SHOULD BE GRATEFEUL THAT THE SEISMIC RELEASE IS OCCURRING SO THERE WILL NOT BE A MAGMA ERUPTION?
I think that is absolutely correct. I think that earthquakes and the gas release and the eruptions of the geysers – that’s all part of the way the system works. It’s all the way that pressure is released at Yellowstone and heat is transmitted to the surface. That magma has a lot of heat in it and the heat is transmitted to the groundwater and it’s transmitted to the geyser system and that causes earthquakes and that’s the way the system seems to have operated for thousands and thousands of years.
All indications are that throughout Yellowstone’s history, the less explosive lava flows are dominant and much more common. The big explosive events are much more rare.
THAT’S WHAT YOU EXPECT OUR FUTURE TO BE WITH YELLOWSTONE PARK?
Yes, the most likely thing we will see in terms of volcanic eruptions at Yellowstone are large lava flows that could come out along the caldera margin and even within the center of the caldera. For any kind of event to occur, there is going to have to be a lot of rock breaking to form the conduits through which the magma will rise. So we would expect a lot of large earthquakes, much larger than the ones we see during these typical seismic swarms.
WHAT SIZE?
We would expect to see a lot of earthquakes over magnitude 5. So, generally ten to 100 times more energy released than the earthquakes associated with these current swarms.
Could Yellowstone Caldera Blow Up Again?
ARE WE OVER DUE FOR SOMETHING GIGANTIC BLOWING UP IN YELLOWSTONE PARK AGAIN?
Well, no, we don’t think that – we don’t believe that Yellowstone is overdue in any sense. These caldera systems can be active – they can produce one or more eruptions – they don’t have to. Some of them produce only one caldera-forming event.
Will there be more volcanic eruptions in the Yellowstone area? Yes, there definitely will be when you look at geologic time. There will be events again. Some of them might be lava flows that are relatively non-explosive. That would be most likely.
We can have more explosive eruptions and certainly on Earth, there will be very large eruptions similar to those that have happened at Yellowstone and those will happen again. And they could happen at Yellowstone, but in terms of the timing of that sort of event – probably very unlikely over the next – over our lifetimes and maybe even over tens of thousands of years.
640,000 Years Ago: A Blast of
240 Cubic Miles from Yellowstone Caldera
Oblique view of Yellowstone Caldera © 2000 Robert B. Smith.
IN THE LAST BIG CALDERA EXPLOSION 640,000 YEARS AGO, HOW MUCH IN TERMS OF SQUARE MILES, WAS AFFECTED BY LAVA AND ASH AND WHAT WAS THE SIZE OF THE BLAST FROM THE CALDERA?
Well, the blast 640,000 years ago was truly enormous and one of the larger ones we’ve seen in the geologic record. It covered many hundreds of square miles with thick deposits close to Yellowstone, and then many thousands of square miles with ash as you move away from Yellowstone. There’s no doubt that if you were within several hundred miles of Yellowstone during one of those older eruptions, things would have been very disrupted. In fact, if an eruption happens like that anywhere in the world, it will disrupt air traffic globally and certainly the rivers draining any area near one of those eruptions will be disturbed for many, many years. So, such eruptions are globally-affecting events. They are a big deal. Fortunately, they are not very common.
HOW MANY CUBIC MILES OF DIRT AND ASH AND ROCK WENT UP OUT OF THE YELLOWSTONE CALDERA?
Right, 640,000 years ago it's estimated that 240 cubic miles blasted out of the Yellowstone caldera. That works out to be about a thousand cubic kilometers and that’s enough material, for example, to bury the state of Texas beneath about 5 feet of debris. That’s a lot of material!
Huge Yellowstone Eruption
Would Effect Whole World
WHAT WOULD THAT HAVE DONE TO THE ATMOSPHERE OF THE EARTH AND CLIMATE?
It depends on how much sulfur gas got out during the eruption and how much of it got high up in the atmosphere. Certainly, it would have cooled the planet several degrees. The thought is the effect might last for a decade, possibly even longer. So, even smaller volcanic eruptions that release a lot of sulfur can have a sizeable effect on the short-term climate.
IN 2010 GOING FORWARD INTO THE FUTURE, WE HAVE SO MANY MORE HUMANS AND ANIMALS ON THE PLANET THAT IF THE YELLOWSTONE CALDERA DID ERUPT AS IT DID 640,000 YEARS AGO AND COVERED A THOUSAND SQUARE MILES WITH THICK LAVA AND ASH, THAT WOULD TAKE OUT A LOT OF POPULATION TODAY, WOULDN’T IT?
Certainly that kind of an event, if it happened today – yeah, it would be very, very damaging and destructive to our country. If a similar event happened in other countries, the same thing – and it would have global implications. Nobody doubts that.
Saving Humans Before Such An Eruption?
DO YOU THINK THERE IS ANY WAY TO GET THOUSANDS AND THOUSANDS OF PEOPLE OUT OF AN AREA LIKE YELLOW STONE PARK AND MONTANA AND WYOMING AND THE CANADIAN REGION IN TIME IF YOU WERE GETTING STEAM AND RUMBLINGS AND YOU KNEW THAT MOLTEN LAVA WAS COMING UP TO THE SURFACE – WOULD THERE BE TIME TO GET ALL OF THAT POPULATION OUT?
There are a lot of scenarios for eruptions at Yellowstone and a lot of those scenarios do not involve the worst-case scenario. Probably 9 out of 10 eruptions at Yellowstone, there would be no need to be moving people out of Montana and Wyoming. You’d just need to get the people out of Yellowstone National Park because these lava flows – while they are damaging within the park – are not something that is going to affect wide, wide areas.
Now, certainly if we knew the worst case scenario were about to happen, it would depend upon how much time we had and nobody knows for sure how long the build up is before one of these large eruptions.”
Fate of Yellowstone Park
Over the next million years, Yellowstone is expected to cool down like the lava in Arco, Idaho's Craters of the Moon. Volcanic eruptions first occurred at Craters of the Moon about 15,000 years ago. The most recent eruptions ended about 2,100 years ago and were likely witnessed by the Shoshone people. A Shoshone legend speaks of a serpent on a mountain who, angered by lightening, coiled around and squeezed the mountain until liquid rock flowed, fired shot from cracks, and the mountain exploded. The volcanic area now lies dormant, but its eight eruptive periods formed 60 lava flows which traveled as far as 45 miles from their vents.
Craters of the Moon is in the Picabo Volcanic Field 29 kilometers southwest of Arco, Idaho.
More Information:
For more information about seismic and volcanic events, please see Earthfiles reports in the Earthfiles Archive:
• 07/27/2006 — San Andreas Fault So Stressed, Next Quake Could Be Magnitude 8
• 04/20/2005 — Outer Space Impact At Serpent Mound, Ohio, 256 Million Years Ago
• 03/10/2005 — Juan de Fuca Ridge: 4,000 Small Quakes West of Vancouver Island, Feb. 27 - Mar. 4.
• 02/04/2005 — Swarms of Earthquakes in Ecuador and the Nicobar and Andaman Islands - Is There A Connection?
• 01/07/2005 — 9.0 Sumatra Earthquake Update
• 09/27/2004 — Earthquake Swarms At Mt. St. Helens, Washington
• 12/13/2003 — Yellowstone Is Still An Active Volcano
• 09/19/2003 — Yellowstone Park - Will There Be Another "Super Volcano?"
• 08/30/2003 — Volcanic and Seismic Threats to Northwest U. S.
Websites:
USGS Yellowstone Volcano Observatory: http://volcanoes.usgs.gov/yvo/
USGS Current Volcano Alerts: http://volcano.wr.usgs.gov/activity/status.php
University of Utah Seismograph Stations: http://www.seis.utah.edu/
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