(bright music)
Hi everybody, I'm Mike Poland,
the scientist in charge of
the Yellowstone Volcano Observatory
and this is the YVO monthly update
for September 1st of 2021.
Coming to you today from the Upper Geyser basin
in Yellowstone National Park,
not far from Old Faithful,
and this is Morning Glory Pool in the background behind me.
And Morning Glory has a sort of a cautionary tale to tell
about how humans can impact
the way thermal features look and behave.
Morning Glory used to be a beautiful, deep blue color,
of course named after the flower,
but it was right next to the road
that came into the Old Faithful area
so it was very heavily visited.
And people would have a tendency
to throw things into the pool,
rocks, coins, handkerchiefs, all kinds of random things.
In fact, the pool earned
the nickname "The Garbage Can" for a while,
there was so much stuff that was thrown into it.
And in fact this clogged the input,
the thermal input to the pool,
and that resulted in the pool lowering its temperature
and thermophilic bacteria began
to occupy different parts of it.
So the plumbing of the pool changed
and that changed the color from that deep blue
to this sort of colorful pattern that we see today.
Now in 1970s,
the Park actually siphoned out some of the water
and cleaned up some of the garbage.
They pulled out something like $90 in change,
over $86 in pennies alone,
as well as over 70 handkerchiefs,
all kinds of things like that.
And then of course when they let the water back in,
it never really came back
to that nice deep blue Morning Glory color.
So an unfortunate tale about how humans
can alter these thermal features just by throwing things in.
And that's of course why that's not something
we do here in Yellowstone.
Okay. Well, now let's talk about
what happened during the past month
in terms of volcano and earthquake activity
in the Yellowstone area.
For those of you that follow Yellowstone seismic activity,
you know that it's been a pretty busy summer.
There were a lot of earthquakes located in June and July,
especially July when there were over 1000 earthquakes
that were located.
And that is the most number of earthquakes
since June of 2017
when there were over 1100 that were located.
Well August saw a return to background levels of seismicity.
The University of Utah Seismograph Stations,
they're responsible for the operation and maintenance
of the Yellowstone seismic network,
located just 97 earthquakes during the month of August.
The largest was a magnitude 3.1 here
just to the west of the Norris Geyser basin.
And this occurred on August 20th.
Now this region between Hebgen Lake and Norris sees
most of the seismicity in the region.
So it's no surprise that that largest earthquake,
a small earthquake M3.1 occurred in that area.
There was a little bit of seismicity
beneath Yellowstone Lake.
This is in the area of July's rather large swarm,
but none of the activity in Yellowstone
during the month of August qualifies as a swarm.
And that's because none of it occurred
in a short period of time all in the same place.
So a smattering of earthquakes, sort of aftershocks
from the swarm that occurred in July,
but no swarm activity in the Yellowstone region
during the month of August.
We didn't see any changes in deformation
in the Yellowstone region.
It's been pretty steady over the past several years.
This is GPS station at the White Lake area
that's on the Sour Creek resurgent dome
in the east part of the caldera.
Vertical deformation over the last two years
with each one of these blue dots indicating the day.
Downward trends indicate subsidence
and upward trends indicate uplift.
Now over the past couple of years,
we've seen overall subsidence of just a few centimeters,
an inch or two.
Now every summer,
there's a bit of an interruption in that subsidence pattern.
You can see here during the summer of 2020,
and again during the summer of 2021.
And that's caused by groundwater
that percolates down into the subsurface
and the surface sort of soaks it up like a sponge.
And we get a little bit of uplift or a pause
in that subsidence.
So that's what's occurring every summer
and we're seeing it again in the summer of 2021.
It's the same story on the other side of the caldera,
the west side of the caldera
and the Mallard lake resurgent dome.
This is a GPS site near Old Faithful.
Again, the last two years,
and each one of these blue dots is one day.
There's this overall subsidence trend,
but we can see over the past summer,
we've seen a pause in that subsidence,
perhaps even a very slight amount of uplift,
maybe just a centimeter,
just a fraction of an inch, due to all that groundwater
from snow melt that's percolating into the subsurface.
The signal over the past year
has gotten a little better at this site
because a fire in 2020 resulted
in a thinning of the trees in this area.
And it was done intentionally to reduce
the fuel load near Old Faithful.
And that resulted in a better signal reaching
the GPS antenna and so a cleaner data set.
And finally moving over to the Norris Geyser basin.
We haven't seen any changes in the last year and a half or so.
And Norris had been going up from 2015 to 2018.
It didn't do too much from 2018 to 2019,
a little bit of subsidence here right at the end of 2019
but since early 2020,
Norris has been very steady,
no real up or down motion in the Norris area.
So Norris remains quiet.
And then turning to everyone's favorite Geyser
in the Norris Geyser basin,
Steamboat Geyser, the largest geyser in the world.
It went an entire month without an eruption.
And what you're seeing here is
the temperature measured in the Steamboat outflow channel.
And these variations here are just daily variations.
It gets warmer during the day and cooler overnight.
So no real activity to speak of during these time periods
where the temperature is just going up and down
with the temperature of the day.
Toward the middle and end of the month,
we see more of this kind of spiky behavior.
And this is caused by an increase in minor erupt activity
at Steamboat Geyser.
We tend to see an increase in minors
before there is a major eruption.
So this may suggest we're on the road
to another major eruption,
the last one was on July 8th.
So it's been well over a month, month and a half,
possibly even two months by the time we get one.
This is in stark contrast the previous few years
when we had major eruptions every five to 10 days or so.
And it really suggests that Steamboat activity is waning.
It may be going dormant again soon,
but perhaps not quite yet.
This minor activity suggests we may be on our way
to a major eruption sometime in the month of September.
Well, that does it for the monthly update.
Now, remember if you have any questions,
you can email us anytime at yvowebteam,
that's all one word,
@usgs.gov.
Stay safe, stay healthy,
and we will see you next month.
Take care.
(bright music)