November (2021) Yellowstone Volcano

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Detailed Description

The November 2021 YVO Yellowstone Volcano update comes to you from a very snowy Norris Geyser Basin with a story about Porkchop Geyser’s 1989 explosion.

Porkchop Geyser was named in the 1960s because it had a shape that looked a lot like a pork chop. In the 1970s to 1980s, it started having intermittent geyser eruptions, becoming more and more active. On September 5, 1989, Porkchop Geyser exploded. The vent for the geyser became so constricted that its pressure increased and it blew up. Rocks were thrown 200 feet from geyser and are visible around the geyser today. A lot of people witnessed the hydrothermal explosion, and the potential hazard is one of the reasons thermal basins are carefully monitored. But since 1989, Porkchop's been a relatively calm pool.

During the month of October, seismicity in Yellowstone was at background levels. The University of Utah Seismograph Stations, which is responsible for the operation and maintenance of the Yellowstone seismic network, located 267 earthquakes in the region. The largest was a magnitude 2.6, located just to the east of the Norris Geyser Basin. There were three swarms in the region, one north of the Old Faithful area, one east of Norris, and one northeast of West Yellowstone, Montana.

For deformation, there is a downward trend (subsidence) of several centimeters or about an inch per year that has been recorded at the White Lake GPS station over the past two years; there are pauses in subsidence during the summer caused by seasonal groundwater recharge. The same is true at the Old Faithful continuous GPS site. In the Norris Geyser Basin, it appears that the area may be returning to a period of uplift, after a few years of no deformation.

At Steamboat Geyser, there were two water eruptions, on October 13 and 25, for a total of 17 eruptions this year.

For questions, email yvowebteam@usgs.gov.

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Length: 00:05:49

Location Taken: WY, US

Video Credits

 

Video edited by Liz Westby

Transcript

- Hi, everybody. I'm Mike Poland, the scientist-in-charge of the Yellowstone Volcano Observatory. And this is the monthly update for November 1st, 2021. 

Coming to you today from a very snowy Norris Geyser Basin. And we're looking at Porkchop Geyser. Now Porkchop was named in the sixties because it looked like a pork chop. It was really just sort of a thermal pool, but in the seventies and into the eighties, it started having these intermittent geyser eruptions. It became Porkchop Geyser. And in the mid-eighties, it started having these perpetual geyser eruptions. In fact, there's some really spectacular photos from the eighties, especially in the winter - days like today where large mounds of ice would form over the geyser as the water that was coming out, as the steam condensed very quickly into ice crystals, you got these very spectacular ice mounds.

And Porkchop was becoming more and more active through the late eighties until on September 5th, 1989, it actually exploded. The vent for the geyser became so constricted that pressure built up and it blew it up. And rocks were actually thrown 200 feet distant from there. In fact, all those upturned rocks that you see around Porkchop now were formed during that explosion. And there were a bunch of people in the geyser basin that day who witnessed it. So we have a very good record of the Porkchop explosion. 

This is an example of a hydrothermal explosion, a relatively small one, but this is one of the hazards that we have in Yellowstone. And one of the reasons that we need to monitor the thermal basins like we do. So since that explosion in 1989, Porkchop's been a relatively calm pool. You can see the nice blue color there. We actually monitor the temperature with one of our thermal data loggers And you can find that information on the Yellowstone Volcano Observatory website. So, really cool feature here on a wonderful day in Norris Geyser Basin. 

All right, now let's talk about what happened in Yellowstone during the month of October, with respect to earthquake and deformation activity. Seismic activity during the month of October in the Yellowstone region was pretty typical of normal background levels. The University of Utah Seismograph Stations, which is responsible for the operation and maintenance of the Yellowstone seismic network, located 267 earthquakes in the region during the month. The largest was a magnitude 2.6, located just off to the east of the Norris Geyser Basin. That occurred on October 4th, local time. There were also three swarms in the region. One that was sort of north of the Old Faithful area. That was 109 earthquakes in this swarm here. That was a continuation of a swarm that started in September and lasted into mid-October. There was a swarm off to the east of Norris that included the largest event of the month, a little over 20 earthquakes. And then there were also a little over 20 earthquakes in the swarm that was off to the northeast of West Yellowstone, Montana. That's also a continuation of a swarm that started in September and lasted into early October. So normal background seismicity for the month. Largest magnitude 2.6 and typical swarm activity. 

Turning now to deformation. This is showing vertical deformation at the White Lake GPS station over the past two years. This is on the east side of the caldera on the Sour Creek resurgent dome. Each one of these blue dots represents one day. And over the entire two year time period, you can see this downward trend overall, which indicates subsidence. There are periods during the summertime of pause in the subsidence, even a slight amount of uplift, and that's caused by seasonal groundwater recharge. So no real changes in trend over this time period here. We're seeing subsidence on the order of a couple of centimeters about an inch or so per year. If we go to the other side of the caldera and the Old Faithful continuous GPS site, this is on the Mallard Lake resurgent dome. We see the same overall downward trend with this small interruption during the summertime. The trend improves in terms of the precision of the data quite a bit here in September of 2020, because some of the trees in the region were cut down because of a nearby fire and the park wanted to reduce the potential fire load if the fire made it into this area. So with fewer trees in the area, the GPS signal is a little bit better in that region. Moving to the area of the Norris Geyser Basin. Over the past two years, there hadn't been much deformation but it's looking like over the summer, we might start to see a bit of uplift here in the Norris area. Over the last few months, this has only amounted to one to one and a half centimeters or so, less than an inch. And this area has been the site of uplift in the past, particularly during 2013 to 2014. And again, from 2015 to 2018. So Norris may be going back into a period of uplift after a few years of no deformation. 

And finally, now turning to everyone's favorite geyser, Steamboat Geyser. It remains active. We've seen two eruptions during the month of October. This is the temperature trend measured in the outlet channel of Steamboat. So these up and down variations are just the normal daily variations. And then we see a lot of this sort of noise in here. Those are minor eruptions that culminate in a major. So here's a major eruption on October 13th. Then it goes quiet again, not much activity, more minor activity, and then another major eruption on the 25th. So Steamboat had these major eruptions on October 13th, October 25th, and we're seeing more minor activity now. So there'll probably be another major eruption sometime in the next few days, to a week or so. So Steamboat remains active so far during the year 2021. We have seen 17 eruptions of the geyser. 

Well, that does it for the monthly update for November 1st, 2021. Now remember, if you have any questions, you can email us anytime at yvowebteam, that's all one word, @usgs.gov. We'll be back next month. So until then, stay safe, stay healthy. We'll see you soon. Bye, bye.