(soft music)
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.