(gentle music)
Hi everybody.
I'm Mike Poland, the scientist in charge
of the Yellowstone Volcano Observatory.
And this is the monthly update for July 1st, 2021.
Today we're coming to you from Norris Geyser Basin
in Yellowstone National Park.
Norris is a pretty interesting geyser basin.
Now most of these basins in the park are either acidic,
driven by steam that brings acid gases to the surface,
and you get features like Mud Volcano,
or they're neutral to basic.
That's where thermal water
brings this neutral to basic fluid to the surface,
and you get features like Grand Prismatic Spring
and Old Faithful, the geysers with cones.
But at Norris, you have a mix of both,
the acidic and the neutral to basic
probably because there's some gases
that are getting entrained with these fluids
and so you get a mix of both types of features.
Now, behind me is actually a pretty interesting feature
in the Norris area, it's Echinus Geyser.
And Echinus is the largest acid geyser in the world.
Now by acid, we're not talking about water
that would instantly burn you if it touches you.
The acidity is somewhere with a pH
of maybe three and a half or so,
that's about like orange juice.
But it's an interesting feature and somewhat unique
because most geysers in Yellowstone and elsewhere
are neutral to basic.
So this is sort of a special type of geyser behind me here.
And Echinus was just a pool for quite a long time,
the late 1800s into the 1940s.
And then it started to erupt quite regularly.
Up through the 1990s,
there were eruptions happening every few minutes to hours.
And then in the mid 1990s, late 1990s, it turned off again.
And we've only seen sporadic activity at Echinus since.
There's occasionally some bursts of activity
like in late 2017, but Echinus has gone back to sleep.
And it's sort of a good example of the dynamic nature
of geysers in the Yellowstone region.
Now, Echinus, the last eruption was in December of 2020,
and we know that that eruption occurred
because there were a couple of spikes
that were recorded in the temperature sensors
that we have here that you can get
on the Yellowstone Volcano Observatory monitoring page.
And it was also captured by the Yellowstone National Park
geology program's trail cameras,
which they put up to track the geysers.
So, Echinus, spectacular geyser,
very unique and quiet for now,
but occasionally has these bursts of activity.
Okay, now let's talk about what happened
during the past month in terms of earthquake
and volcanic activity in the Yellowstone region.
The University of Utah Seismograph Station,
which is responsible for the operation and maintenance
of the Yellowstone seismic network
located 445 earthquakes in the Yellowstone region
during the month of June.
Now this is above average.
Typically we see about 100 to 200 earthquakes per month.
But it's by no means extreme.
Back in February of 2018,
there were over 550 earthquakes that were located.
And to get really crazy, back in June of 2017,
over 1100 earthquakes were located
in the Yellowstone region.
So, this is certainly on the high end,
but still not outside of the historical norms.
The largest earthquake of the month was a magnitude 3.1
that occurred between Norris and Hebgen Lake on June 28th.
And there were four swarms that occurred during the month.
One in this area here, sort of north of Old Faithful,
just to the east of Madison that had over 150 events
that occurred as part of that swarm.
Another 150 events occurred in the swarm
that included the magnitude 3.1
about halfway between Norris Geyser Basin and Hebgen Lake.
Just north of West Yellowstone,
there was a swarm with about 50 events.
And then just on the shores of Hebgen Lake,
there was a swarm here that had 18 events.
Now these swarms typically account
for about 50% of the seismicity in the Yellowstone region,
a bit more this month,
but that's what happens month to month.
Some months, there are no swarms at all.
There haven't been that many swarms yet this year.
A lot of this swarm activity is driven by water
that's moving around in the subsurface
and activating preexisting faults.
And so with all the snow melt,
especially as we're now well into summer,
this may be what's driving some of these swarms.
Moving now to deformation.
We've seen continuation of the trends in the caldera
that have been occurring for the past several years.
This is vertical deformation up and down motion
at the White Lake GPS station for the last two years.
Each one of these blue dots
represents one day's worth of data.
And you can see over the past two years,
the overall trend is one that goes down.
So the caldera has been subsiding.
There are little hiccups in that you can see,
for example, here in the summer of 2020,
the subsidence slowed to basically a stop,
maybe even reversed a little bit,
and we're seeing something similar happening right now.
Now, this is caused by groundwater recharge.
All of that snow melt,
the same thing that might be driving
some of the swarm seismicity we're seeing
also causes the ground to swell just a little bit
as water occupies all the pore space in the subsurface.
So we see pauses in the overall trend of subsidence
and perhaps even a little bit of uplift.
Now, the overall rates here are very, very low.
The subsidence rates
are about two to three centimeters per year.
That's less than an inch or about an inch a year.
And these little pauses account
for basically nothing in there.
If we look back over the last several years,
you can see those trends really show up.
This is the White Lake GPS station,
vertical deformation since 2016.
And you can see pretty much every summer here
in 2016,
2017,
here in 2018,
2019,
2020,
and now starting in 2021,
they're having pauses in this subsidence
and that's due to the snow melt
causing groundwater recharge.
Now, let's look at the last two years of data
from the Old Faithful GPS site.
This is on the other side of the caldera.
There we see the same overall trend of subsidence,
possibly with a bit of pause
or a little bit of uplift right at the end here,
again, caused by that groundwater recharge
as we're entering summer.
And by the way, I've gotten a lot of questions
about why the signal suddenly gets so clean
here in September of 2020.
And that's because the park
had to cut down a number of trees near the station
to reduce the fire load due to a fire
that was burning near Lone Star
and there was some concern
that it might come into this area.
So fewer trees around the site,
much cleaner GPS signal.
We get much better data when that happens.
And then turning to the Norris area.
We haven't seen many changes at all since early 2020.
And that continues to be the case up to today.
So Norris, which had been uplifting in the late 2010s,
in 2020 really just stopped
and hasn't done much of anything
for the past year and a half.
And now turning to everyone's favorite geyser,
Steamboat Geyser, in Norris Geyser Basin.
This is the first month since April of 2018
before the current frequent activity cycle
at Steamboat started,
that there haven't been any eruptions of the geyser.
Now this is the temperature measured
in the outflow channel from Steamboat.
These variations just show the daily temperature variations,
hot during the day and cooler at night.
And we were perplexed by this.
We didn't see any indication
of minor eruptive activity at the Geyser,
which we knew was going on.
So when we went out to look at the temperature sensor here
on the 28th,
we found that it was actually buried
in over a foot of debris,
which had been washed down the geyser channel.
Once we extracted the temperature probe
and put it back in contact with the water,
we started seeing the warm water that we expected to see
coming down the channel from these minor eruptions.
Now the minor eruptive activity suggests
that we may be in for another major eruption of Steamboat
sometime in the next few hours to days.
But overall, the time between eruptions
has really been lengthening.
The last eruption was on May 31st
and there have only been 12 eruptions so far this year.
And this may be an indication
that the current cycle of activity at Steamboat
is beginning to wane.
And we may be in for another dormant period at Steamboat
coming up soon.
Well, that does it for the monthly update for July.
Now, remember if you have any questions,
you can email us anytime at yvowewebteam,
that's all one word, @usgs.gov.
Stay safe, stay healthy,
and we will see you next month.
Take care.