(mellow music)
Hi everybody.
I'm Mike Poland, the scientist
in charge of the Yellowstone Volcano Observatory
and this is the monthly update for February 1, 2023.
Winter has definitely arrived in the Yellowstone region
and in fact this area is known
for really harsh winter conditions
that go back thousands of years.
During the last ice age,
Yellowstone was actually home to one of the thickest
ice sheets in the continental United States.
There we saw ice that was over half a mile thick
that only started melting out around 14,000 years ago or so.
And of course those harsh winters have continued today
because the Rocky Mountains in that area
are the highest elevation anywhere
in that range on average.
There's also a lot of precipitation that's focused
into that area due to the topography.
So we get a lot of snow, a lot of ice, very cold conditions,
negative 40 degrees Fahrenheit
in places in the interior of the park.
That's harsh for animals, that's harsh for humans,
that's harsh for volcano monitoring equipment as well.
But we've taken specific steps to
try to engineer the monitoring equipment
against these harsh winter conditions.
For example, seismometers are mostly buried,
so that keeps the seismometers more or less immune
to these snowy and icy conditions.
And the solar panels and the radio antennas
that push the data out are at very high levels
above the ground to prevent them getting covered in snow.
Same is true with GPS equipment.
The challenge with GPS though, is that sometimes
the antennas can get covered in ice during conditions
that are really really stormy, and that can cause
the signal to take a little bit longer to get to the antenna
and that makes it actually look like the ground
might be deforming when in fact
it's just ice on the antenna.
And we've got a couple examples of that right here.
This is the GPS dataset from a GPS site
near the Norris Geyser Basin.
So this is vertical deformation.
Each one of these blue dots is one day worth of data.
And you can see this significant deviation
where it looks like the ground went down
and then popped right up again in December of 2021.
And again, a couple more times in November of 2022.
These time periods corresponded to really
intense winter storms in the Yellowstone region
that caused the antennas to ice over
and thus make it look like the ground was actually moving.
But that was just ice on the antenna.
When the ice went away, we popped back up
to where we were before. We can see this sort of effect
to varying degrees throughout the region.
But fortunately it's something
that's recovered rather quickly.
And because we have so many GPS stations in the region,
over 30 in the Yellowstone area
we can use the data from different sites
to make sure that nothing actually is moving.
This is a weather sort of phenomena that we're seeing.
That plus the seismic data, which is always flowing
allows us to really get an idea even in the harshest kinds
of conditions, the dead of winter in Yellowstone
of what's happening beneath the ground surface.
So that's a bit of how we mitigate against
these sorts of effects that we see in Yellowstone,
even though sometimes the GPS data,
we can actually see these big winter storms.
Well now let's talk about what happened over the last month
in the Yellowstone region in terms of seismic activity,
ground deformation, and also geysers.
During the month of January,
activity in the Yellowstone region
remained at normal background levels.
The University of Utah Seismograph Stations
which is responsible for the operation
and maintenance of the Yellowstone Seismic Network
located just 75 earthquakes during the month.
The largest was a magnitude 2.5 that occurred
on January 5th, right at the southern boundary
of Yellowstone National Park.
This was part of a small swarm of 11 earthquakes
that were located in the region
over the course of a two-day period.
There were also an additional 28 earthquakes
that occurred in this area that's sort
of near Norris Geyser basin between Norris
and Mammoth Hot Springs.
This has been an ongoing area of seismicity
for the past many months, since at least last summer.
28 new earthquakes were added to the sequence
that's been ongoing in this area.
But otherwise, activity distributed throughout the region
as it often is with most of the seismicity occurring
in this belt between Hebgen Lake
and north-central Yellowstone National Park.
This is the hotbed of seismicity
for the region historically.
Turning now to deformation.
This is vertical deformation, up and down motion,
at the White Lake GPS station
on the east side of the Caldera.
Each one of these blue circles represents one day of data
and this time series goes back two years.
Downward trends indicate subsidence and upward trends
indicate uplift. The overall trend
during this time period of course is the subsidence
that has been ongoing since 2015.
It's interrupted during the summer months by a pause
in the subsidence or even a slight amount of uplift
and that's caused by runoff from snow melt
that sort of puffs up the ground as the ground
soaks up that water like a sponge.
But the overall trend is about two to three centimeters
per year of subsidence.
That's about an inch per year of subsidence.
And you can see after the end of summer 2022
that continued.
There are a number of little offsets here in the wintertime
and that's caused by snow and ice accumulation
on the antenna, which disrupts the GPS signal a bit.
If we move over to the western side of the Caldera
and the Mallard Lake resurgent dome
this is a GPS site near Old Faithful.
And that same overall trend is apparent,
subsidence of about two to three centimeters,
about an inch or so per year, interrupted
during the summer months by a small amount of uplift
or a pause in that subsidence with, of course
the winter storms.
At Norris Geyser Basin, we haven't seen much
in the way of any deformation, up or down motion,
over the past several months.
This is the two-year plot at Norris.
There's the summer uplift, lots of winter storms
that are manifested as small amounts of subsidence,
but then really nothing since the end
of the past summer at the Norris area.
That's remained steady.
And finally looking at Steamboat Geyser
everybody's favorite geyser, the tallest geyser
in the world.
This is the temperature record in the geyser outflow.
We started January with a lot of minor geyser activity,
that's a lot of this up and down motion here,
with a major eruption that occurred on January 5th.
And then the temperature went back down
to air temperature, of course, right around freezing.
We saw minor activity pick up in mid-January,
culminating with a major eruption here on January 28th.
And then back down to air temperature readings
as the geyser stopped even having little minor eruptions.
So two eruptions to start the year with Steamboat.
I guess that means it's not quite done yet
putting on a show for visitors to Yellowstone National Park.
Well, that does it for the monthly update
for February 1, 2023.
Remember, if you have any questions at all
you can feel free to email us anytime
at yvowebteam, all one word, at usgs.gov.
Stay safe, stay healthy, stay warm
and we'll see you next time.
Bye-bye.
(mellow music)