April 26, 2019– Mary Greeley News – YELLOWSTONE volcano is under the threat of an earthquake dubbed “the big one” by a USGS scientist during a lecture on the supervolcano.
The Yellowstone volcano sits in between the states of Wyoming, Montana and Idaho, inside the Yellowstone National Park in the US. The caldera is labeled a super-volcano due to its potential to create devastation on a global scale. It last had a super-eruption some 630,000 years ago, but there has been a great deal of smaller activity since then.
Super-eruptions have been known to happen following large regional earthquakes as they trigger unrest at the nearby volcano.
Jacob Lowenstein, a leading scientist in charge of monitoring Yellowstone revealed during a lecture at Menlo Park, California, how this has happened before and threatens to happen again should the earthquake measure in at more than six on the magnitude scale.
Before a volcano erupts, there are usually signs of what’s to come; small earthquakes, heat emission, and ground swelling, to name a few, have all been observed to precede eruptions. Volcanologists also monitor the changing composition of gas emissions at volcanoes in the months leading up to an eruption.
The ‘Yellowstone plume’ is deeply rooted at the core-mantle boundary even if they have no tomographic evidence for such a setting. Nonetheless, this hypothesis and the ‘primary’ plume characteristics are further supported by the Columbia River flood basalt in addition to the hotspot track.
He said in 2014: “A lot of earthquakes have occurred at Yellowstone over the past 25 years – just a representative sampling.
“You’ll see there’s a lot of earthquakes out here near Hebgen Lake.
“That’s probably because it’s near the location of the 7.5 magnitude earthquake that occurred in 1959.
“Occasionally there is a big one, and there might be one in the Yellowstone area every 100 to 300 or 400 years.”
Dr Lowenstein went on to reveal how earthquake activity must be monitored due to the threat it poses.
He added: “The last big one was in 1959 and caused a big landslide, killing around 20 people.
1959 M7.5 Hebgen Lake Earthquake Damage
The most recent major events are the 1959 M7.5 Hebgen Lake, Montana, the 1975 M6.1 Norris Junction earthquake, and the 1983 M7.3 Borah Peak earthquakes, Idaho.
The Hebgen Lake and Norris Junction earthquakes occurred 25 km north to and within the 0.63 Ma old Yellowstone Caldera, respectively.
Moreover, GPS observations combined with levelling and InSAR observations reveal alternative uplift and subsidence up to 2 cm yr−1, commonly interpreted as recharge and discharge episodes of the crustal magma reservoirs and are furthermore directly linked to the presence of a mantle plume.
Similarly, earthquake swarms are considered triggered by fluid activity in dyke’s correlating seismic activity and periods of uplift and subsidence.
Just 90 km or 56 miles below the earth surface the maximum temperature close to the plume axis reaches 1510◦C, or 2750 degrees Fahrenheit that is, extremely close to the reported mantle solidus temperature of 1500 ◦C at 3 GPa.
“This is a geologic hazard that’s again much more present in the area than a volcanic eruption.
“People living in the area should be familiar with it.”
It is not the first warning the scientist has given, though.
He previously warned of a “pressure cooker” hazard that could prove catastrophic, referring to hydrothermal explosions.
These occur when superheated water trapped below the surface converts rapidly from liquid to steam.
Rock thrown out from Hydrothermal Explosion
Boiling water, steam, mud, and rock fragments called breccia are ejected over an area of a few meters up to several kilometers in diameter.
Dr Lowenstein said: “There were a lot of these events within the past 15,000 years at Yellowstone.
“The largest of them form Mary Bay within Yellowstone Lake and it’s two miles across.
“So, if you think about the way geothermal systems are established, the boiling temperature of water at the surface is 100C or 212-degree Fahrenheit
“At Yellowstone, you’re at a higher elevation and it’s about 92C or 194-degrees Fahrenheit, but as you go down the pressure increases and so does the boiling temperature – like a pressure cooker.
“So, if that system depressurized, you’ll get water that’s way above its boiling point and it will catastrophically explode into steam – breaking rocks along the way and forming these very interesting landforms.”
He also revealed how the last explosion of this magnitude happened over 3,000 years ago it may be overdue a volcanic eruption too.
He said during the same lecture: “Since the last caldera-forming eruption (630,000 years ago), there have been lava flows and, in some cases, very big lava flows beneath the topography.”
There have been 80 eruptions since the last major eruption.
New Thermal Hot Spot
Addressing a model of the landscape, he added: “This is one of the largest ones – it’s called the Pitchstone Plateau – and it’s about the size of Washington DC.
“It’s anywhere from about 50 to 400 feet in thickness and it’s 70,000 years old.
“So, this is actually the last volcanic eruption at Yellowstone.”
A plateau is an area of highland, usually consisting of relatively flat terrain, that is raised significantly above the surrounding area, often left behind from an eruption.
The specialist detailed that if history repeats itself it would be a problem on a local scale.
He added: “Since that time, there has been no volcanism at Yellowstone.
“If something like this happened today it would be a big deal.
“It would not have a lot of explosive activity and it would not be a national-scale emergency.
“It would be very much a local event, but it would still be very spectacular.
“These events normally occur every 10,000 years and appear in groupings.
“But the last one was 70,000 years ago.”
There have been 80 smaller eruptions since the last major eruption.
The vertical impingement of the Yellowstone plume into the 200– 300 km thick cratonic lithosphere indicates that the lower half of the craton is delaminated at the same velocity that the axis of the plume migrates with respect to the American continent. On Earth, there is no other example of a so fast delaminated lithosphere.
credit: In part with https://admin.express.co.uk/news/science/1119312/yellowstone-volcano-usgs-scientist-warning-big-one-earthquake-spt