(gentle music)
Hi everybody, I'm Mike Poland,
the scientist in charge
of the Yellowstone Volcano Observatory,
and I'm coming to you from Yellowstone National Park
with the monthly activity update for September 1st of 2020.
I'm actually on the North side of Yellowstone Lake,
you can see Yellowstone Lake just there in the distance.
And I'm standing in front of a small circular pond.
This pond actually represents one of the underappreciated
volcanic hazards in the Yellowstone region.
It's a small hydrothermal explosion crater,
and this is where steam builds up beneath the surface,
water flashes to steam, and there is an explosion.
These happen on a small scale in Yellowstone,
every so often leaving a crater,
oh, say maybe just a meter or so across,
but there are much larger hydrothermal explosion craters
that form once every few thousand years or so.
This one behind me, formed about 3000 years ago.
So this isn't actually any magma reaching the surface.
It's not a volcanic eruption,
but these hydrothermal explosions can happen
from time to time in Yellowstone.
And actually some of the largest known
hydrothermal explosion craters in the world
are right here on the North side of Yellowstone Lake.
So a really fascinating process here,
and a good example of it right here near Yellowstone Lake.
Okay.
With that, let's dive into the data
and talk about what happened
during the month of August 2020.
It was another quiet month for seismicity
in the Yellowstone region.
The University of Utah Seismograph Stations,
which is responsible for the operation and maintenance
of the Yellowstone Seismic Network
located only 82 earthquakes in the region
during the month of August.
The largest was just off to the West of Old Faithful,
a magnitude 2.6 that occurred on August 20th.
There was also a small swarm of 12 earthquakes
that occurred about 12 miles to the North of Old Faithful.
That occurred on August 18th.
That sort of seismicity is very normal
for the Yellowstone region.
If we zoom out and look at the broader region,
we can see that aftershock sequences are continuing
in central Idaho and near Salt Lake City.
These Salt Lake City aftershocks are associated
with a main shock that occurred on March 18th
and in central Idaho with the main shock,
a 6.5 that occurred on March 31st.
Now aftershock sequences are normal
after large earthquakes like that.
They tend to last longer and be larger
after larger main shocks.
So we see more aftershocks,
stronger aftershocks in central Idaho
than we do in Salt Lake City,
where we can see they're sort of petering out
in the Salt Lake region, but in central Idaho,
they're likely to continue for many, many months more,
since that was a larger earthquake, a magnitude 6.5,
compared to a magnitude that's in the mid fives
for the Salt Lake City earthquake.
These were tectonic earthquakes
and not related to the Yellowstone system.
Turning now to deformation,
we haven't seen many changes over the last several months.
This is vertical deformation at the White Lake GPS Station
on the Sour Creek resurgent dome
on the east side of Yellowstone caldera.
And each one of these dots is one day worth of data.
This particular time series starts today
and goes all the way back to the beginning of 2018.
And this downward trend indicates subsidence,
the ground sinking,
at a rate of approximately two to three centimeters.
That's about one inch every year.
There are some interruptions.
For example, here in mid 2018,
in mid 2019, and again in mid 2020,
where there's not that much deformation.
And those are seasonal fluctuations
that are in superimposed
on this overall trend of subsidence,
which has actually been occurring since 2015.
We see the same thing on the other side,
the west side of the caldera
near the Mallard Lake resurgence dome.
This is a GPS station near Old Faithful
that's showing that same trend of subsidence
by about a couple of centimeters per year.
And that's been ongoing also since about 2015.
The story's a bit different
in the Norris Geyser Basin area.
This is a GPS station located not too far from Norris,
just North of Yellowstone caldera,
and starting in 2018,
you can see there was uplift that paused at the end of 2018,
and after a bit of subsidence in late 2019,
we haven't seen much in the way of changes.
Now, this uplift actually began in 2015.
It paused in 2018 and then haven't seen anything.
So Norris has been a bit more dynamic than the caldera area,
but there haven't been any changes
since the beginning of 2020.
Now, turning to everyone's favorite geyser, Steamboat,
we saw five eruptions during the month of August.
This is the temperature record
for the Steamboat outflow channel.
Whenever you see these normal ups and downs,
that's air temperature.
It means there's no water in the channel.
The geyser really isn't very active.
Before each major eruption,
there's a buildup in minor geyser activity.
The channel is full and we see increasing water temperature.
Then there's a major eruption
and the channel goes dry again,
and we're back to air temperature.
So each one of these major eruptions on August 3rd,
on August 9th, August 14th, August 20th,
and August 26 was preceded by some time period
of minor geyser activity.
So Steamboat just as active as ever.
And if you like geysers, we had a rare treat.
On August 26th, Giantess Geyser,
which is located near Old Faithful,
erupted for the first time in six and a half years.
Now, that's not abnormal.
Most geysers do that sort of thing.
They turn on and they turn off,
but Giantess turned on on a beautiful summer day,
and really gave us a rare treat.
Stan Radensky of Yellowstone National Park
provided these videos.
So thank you, Stan, and thanks, Giantess,
for giving us a show just last week.
Well, that does it for the monthly update
for September 1st of 2020.
Now, remember if you have any questions,
you can always feel free to email us at yvowebteam,
that's all one word, @usgs.gov
Hope you're all staying safe and healthy,
and we'll see you next month.
Take care.
(gentle music)
