(gentle music)
Hi everybody, I'm Mike Poland,
the scientist-in-charge
of the Yellowstone Volcano Observatory,
and this is the monthly update for October 1st, 2022.
We're going to start this update out with the third
in our three part series
on the different types of thermal features in Yellowstone.
Back in August, we talked about travertine features,
which we find in the Mammoth Hot Springs area.
Last month we talked about neutral chloride features;
things like Old Faithful and Grand Prismatic Spring.
And this month, we're coming to you from Artist Paintpots,
to talk about the third type of feature,
acid sulfate springs.
Now these features start as snowmelt and rainwater
percolate deep into the earth.
They get heated by the magma chamber that's cooling
well beneath the surface,
and then that water starts to rise.
It picks up gases that are emitted
by that cooling magma body as well.
Now as the water starts to get close to the surface,
it might begin to boil.
Now the water itself will go off
and form one of these neutral chloride features
like Grand Prismatic Spring or Old Faithful.
But the gas, as it boils, can separate,
and that gas is a bit acidic
because of the carbon dioxide in it.
Now, as that gas rises separately to the surface,
it starts to dissolve some of the rock
because it has that slightly acidic pH.
And as it dissolves that rock,
it turns it into this white kind of chalky clay.
And as it mixes with little bits of water
that's at the surface or just beneath the surface,
we get paintpots, just like this.
So these sorts of features are mostly driven by gases
that come off of that water
that's been all the way down to the magma chamber
and risen all the way back to the surface.
All right, now let's talk about the seismic, deformation
and geyser activity
that's happened during the month of September.
During the month of September,
earthquake activity was slightly elevated
in the Yellowstone region.
Now typically we see about 150 to 200 earthquakes per month,
but in September,
the University of Utah Seismograph Stations,
they're responsible for the operation and analysis
of the Yellowstone Seismic Network,
they located 678 earthquakes in the region.
Now this may sound like a lot,
but it's actually not even the most earthquakes
we've come close to in a given month.
A few years ago, we had more than a thousand earthquakes
a month happening in Yellowstone,
and even just last year in 2021,
there were months with over 800 earthquakes.
Now 510 of those 678 earthquakes occurred right here
in the area between Norris Geyser Basin
and Mammoth Hot Springs.
This is the Grizzly Lake swarm of earthquakes
that's been going on since late July,
and the largest earthquake of the month,
a magnitude 3.9 on the morning of September 18th,
occurred as part of this swarm.
Now this belt of seismicity from Hebgen Lake
into the north central part of Yellowstone National Park
is by far the most seismically active part of the region.
In fact, in 2017 there was a three-month-long swarm
that occurred just to the west of the current swarm.
That was the Maple Creek earthquake swarm.
That had 2,400 located earthquakes
over that three-month period,
the largest of which was a magnitude 4.4.
Just to put this swarm here in context,
we've had about 800 or so earthquakes
in this particular Grizzly Lake swarm,
since it began in July, and it's continuing into August.
So this is one of these long-lived swarms in Yellowstone
that's a result of water interacting
with pre-existing faults,
which really are present all through the area.
There are a few other swarms in the region during the month.
For example, this small one here,
just in the Lake area,
this one here, north of the Old Faithful area,
and then this one on the south side of Lewis Lake.
All those swarms had about a dozen events or so each.
So slightly elevated month for seismicity,
but nothing unprecedented,
mostly due to this swarm of earthquakes
occurring near Grizzly Lake.
In terms of ground deformation,
we're seeing the seasonal trend that we expected to see
that has just taken place in the month of September.
Now this is vertical deformation
at the White Lake GPS station
on the east side of the caldera
in the Sour Creek resurgent dome.
Plot spans the last two years,
and each one of these blue dots is one day of data.
Downward trends indicate subsidence
and upward trends indicate uplift.
Now the overall trend,
even stretching all the way back to 2015,
is of subsidence of about two to three centimeters
or about one inch every year.
But that's interrupted in summer months
by a pause in the subsidence,
or even a slight amount of uplift.
You can see it here in the summer of 2021,
and again here in the summer of 2022.
Now that's caused by groundwater.
That's water that's mostly percolating from snowmelt,
gets into the surface slowly, the subsurface slowly,
and it causes the ground to sort of puff up like a sponge.
So every summer as that snowmelt percolates
into the subsurface,
we get a little bit of uplift
or at least a pause in the subsidence,
but then it turns around by late summer or early fall.
That transition began here in the May-June timeframe,
where we saw the little bit of uplift,
and then right here in mid- to late-September
is when we saw the transition back to subsidence.
The exact same story is what we see
over on the other side of the caldera.
This is the Old Faithful GPS site
near the Mallard Lake resurgent dome.
Overall subsidence interrupted in the summertime
by these trends
of a slight amount of uplift,
but you can see the same transition
from that slight amount of uplift
back to the subsidence that's been ongoing since 2015.
Occurred right here in mid-September
near the Old Faithful site.
Also at Norris,
the same story remains true.
Norris hasn't seen as much subsidence as the caldera.
Really not a whole lot of change here in 2021.
A little bit of uplift during the summer of 2021,
then back to subsidence.
This deviation right here at the end of 2021
is due to a winter storm that buried the antenna
in snow and ice.
Little bit of uplift here again in 2022 summer,
and then the transition is occurring now in mid-September
to go back to that subsidence trend.
So we're not seeing a whole lot of new deformation
in the Yellowstone area,
really just looking back at those normal trends
of subsidence in the caldera,
not much deformation at Norris,
and the season out signal,
which is transitioning back to subsidence
now that we're entering the fall season.
And finally looking at the tallest geyser in the world,
Steamboat Geyser in the Norris Geyser Basin.
This is the temperature measured in the outflow channel
from Steamboat.
All of this variability you see in the high temperatures
in the early part of the month
are due to minor eruptive activity.
That's when the water is splashing,
few tens of feet maybe above the geyser pretty constantly,
not a major eruption,
but it sort of goes along, goes along,
and then September 18th,
that's when we have a major eruption with the geysering
that can go up hundreds of feet.
And after that you can see the temperature drops
quite a bit,
and then we go into these daily variations.
This is when the outflow channel is essentially dry.
There's no more minor activity,
and we're just seeing daily temperature variations here.
So typically we see some minor activity
that leads up to a major,
like you can see here in the early part of the month.
We're not seeing any of that minor activity now,
and that suggests that there isn't a major eruption
of Steamboat that is imminent.
Hopefully though, we'll start to see some minor activity
in October,
and maybe leading up to another major this year.
This is the ninth major eruption of 2022,
and this is well behind the pace
that was set in 2018, 2019, 2020, and 2021.
So it seems that the geyser may be waning
and perhaps is heading back into slumber,
but hopefully it's not done just quite yet.
Well, that does it for the October update.
Now remember, if you have any questions
you can email us anytime
at yvowebteam, all one word, @usgs.gov
Until next month, stay safe and stay healthy.
We'll see you later.
Bye bye.
(gentle music)