Yellowstone Volcano Observatory Monthly Update for November 2020

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Mike Poland, Scientist-in-Charge of the Yellowstone Volcano Observatory, gives an overview of activity at Yellowstone during November 2020.
 

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Length: 00:05:21

Location Taken: Vancouver, WA, US

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Video edited by Liz Westby
 

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- Hi everyone. I'm Mike Poland, the scientist in charge of the Yellowstone Volcano Observatory and this is the monthly update for December 1st of 2020. Now before we get into talking about the monitoring data from the last month, I thought it might be fun to talk about the world's most famous geyser, Old Faithful. Most of us know Old Faithful as this very regular geyser, it erupts every hour and a half. But that didn't always use to be the case and in fact, there's some new research that suggests that there was a time when Old Faithful wasn't faithful at all. Now when it was first scientifically described in the 1870s, Old Faithful was erupting about every 60 to 70 minutes and that stayed mostly true through the 1950s. After a series of earthquakes starting with the 1959 magnitude 7.3 Hebgen Lake earthquake just outside the park, that interrupt interval between eruptions lengthened a little bit over time. And that gets us to our current interval today which is about 94 minutes plus or minus 10 minutes or so. About 2% of eruptions are very short duration, only about two-minute eruptions instead of the usual three to four minutes. And these eruptions are actually followed by very short intervals, only about an hour between eruptions which sorta makes sense, the geyser might not have erupted that much so it took less time to refill. But there's been new research that has looked at mineralized wood samples from the geyser cone itself. Now we know that trees are not gonna be growing on a geyser because of all that hot water, it kills them. So those trees must've grown at a time when Old Faithful was dormant and so by looking at the age of the trees, there were a number of tree specimens that were sampled. Scientists found a period about 600 to 800 years ago when the geyser must not have erupted at all. This actually corresponds to a period of drought in the region. In fact, drought throughout much of the Western United States. This might've also affected native societies in the Southwestern US. So during periods of heavy drought, when water levels perhaps are quite low beneath Old Faithful, the geyser doesn't interrupt at all. So quite some neat research coming out about Old Faithful and shows us that the times that we've been observing it, the last 150 years or so, it was really just a blip in time for this spectacular thermal feature. Okay, let's talk now about what happened over the last month in the Yellowstone region. The University of Utah Seismograph Stations which is responsible for the operation and maintenance of the Yellowstone Seismic Network located 100 earthquakes in the Yellowstone region during the month of November. That's pretty typical, background rates of seismicity for the area. You can see here that they're scattered throughout the region, although there is a bit of a cluster here between Hebgen Lake and the Norris Geyser Basin and that's pretty typical, this is the most seismically active area of the park. The largest earthquake of the month was a magnitude 3.1 that occurred as a part of a small swarm of 12 events on November 25th right here on the Western boundary of the park so background rates of seismicity for the month. Turning now to defamation, this is vertical change at the White Lake GPS station which is on the East side of the caldera near the Sour Creek resurgent Dome. Each one of these dots is a single day's worth of data and this plot here spans two years. Downward trends indicates subsidence and upward trends indicate uplift. So you can see over these two years, the overall trend has been subsidence. The ground moving down at a rate of two to three centimeters about an inch or so every year and this trend has been ongoing since 2015. During the summer months, there are pauses in that subsidence due to groundwater recharge but overall, you can see the subsidence has been fairly persistent. Moving now to the West side of the caldera in the Mallard Lake resurgent Dome, this is the GPS station that's located near Old Faithful and the story is pretty much the same. Overall subsidence at rates of a couple of centimeters, slightly less than an inch per year and this has been ongoing since 2015. Now we move to the Norris Geyser Basin where we haven't seen much change, at least since the beginning of 2020. Norris had been uplifting from 2015 to 2018 but that paused in 2018 and since then there hasn't been much change at all, you can definitely see since January of 2020, there's been really no change whatsoever. So Norris defamation continues to be basically flat, no net change in that area. And finally going to everyone's favorite geyser, Steamboat Geyser that remains as active as ever with four eruptions during the month of November. Now this shows the temperature of the water in the geyser's outlet channel. These increases are minor geyser eruptions and they culminate in a spike that's a major eruption. After the major eruption, the geyser effectively goes dry for awhile and we just see air temperature being recorded in the outlet and then minor activity increases again building up to the next major eruption. Well the four major eruptions occurred on November 3rd, November 11th, November 20th and November 29th and with these four eruptions, that brings the grand total of eruptions for the year to 46. Well that does it for the monthly update for December of 2020. Now remember if you have any questions, you can feel free to email us anytime at yvowebteam, that's all one word, @usgs.gov. Hope everyone stays safe and stays healthy out there, just one month to go and then we're done with 2020. Take care everyone and see you in 2021. Bye bye.