WEBVTT

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(mellow music)

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<v ->Hi everybody.</v>

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I'm Mike Poland, the scientist

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in charge of the Yellowstone Volcano Observatory

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and this is the monthly update for February 1, 2023.

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Winter has definitely arrived in the Yellowstone region

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and in fact this area is known

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for really harsh winter conditions

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that go back thousands of years.

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During the last ice age,

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Yellowstone was actually home to one of the thickest

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ice sheets in the continental United States.

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There we saw ice that was over half a mile thick

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that only started melting out around 14,000 years ago or so.

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And of course those harsh winters have continued today

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because the Rocky Mountains in that area

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are the highest elevation anywhere

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in that range on average.

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There's also a lot of precipitation that's focused

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into that area due to the topography.

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So we get a lot of snow, a lot of ice, very cold conditions,

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negative 40 degrees Fahrenheit

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in places in the interior of the park.

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That's harsh for animals, that's harsh for humans,

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that's harsh for volcano monitoring equipment as well.

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But we've taken specific steps to

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try to engineer the monitoring equipment

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against these harsh winter conditions.

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For example, seismometers are mostly buried,

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so that keeps the seismometers more or less immune

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to these snowy and icy conditions.

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And the solar panels and the radio antennas

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that push the data out are at very high levels

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above the ground to prevent them getting covered in snow.

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Same is true with GPS equipment.

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The challenge with GPS though, is that sometimes

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the antennas can get covered in ice during conditions

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that are really really stormy, and that can cause

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the signal to take a little bit longer to get to the antenna

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and that makes it actually look like the ground

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might be deforming when in fact

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it's just ice on the antenna.

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And we've got a couple examples of that right here.

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This is the GPS dataset from a GPS site

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near the Norris Geyser Basin.

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So this is vertical deformation.

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Each one of these blue dots is one day worth of data.

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And you can see this significant deviation

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where it looks like the ground went down

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and then popped right up again in December of 2021.

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And again, a couple more times in November of 2022.

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These time periods corresponded to really

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intense winter storms in the Yellowstone region

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that caused the antennas to ice over

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and thus make it look like the ground was actually moving.

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But that was just ice on the antenna.

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When the ice went away, we popped back up

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to where we were before. We can see this sort of effect

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to varying degrees throughout the region.

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But fortunately it's something

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that's recovered rather quickly.

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And because we have so many GPS stations in the region,

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over 30 in the Yellowstone area

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we can use the data from different sites

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to make sure that nothing actually is moving.

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This is a weather sort of phenomena that we're seeing.

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That plus the seismic data, which is always flowing

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allows us to really get an idea even in the harshest kinds

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of conditions, the dead of winter in Yellowstone

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of what's happening beneath the ground surface.

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So that's a bit of how we mitigate against

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these sorts of effects that we see in Yellowstone,

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even though sometimes the GPS data,

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we can actually see these big winter storms.

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Well now let's talk about what happened over the last month

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in the Yellowstone region in terms of seismic activity,

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ground deformation, and also geysers.

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During the month of January,

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activity in the Yellowstone region

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remained at normal background levels.

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The University of Utah Seismograph Stations

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which is responsible for the operation

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and maintenance of the Yellowstone Seismic Network

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located just 75 earthquakes during the month.

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The largest was a magnitude 2.5 that occurred

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on January 5th, right at the southern boundary

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of Yellowstone National Park.

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This was part of a small swarm of 11 earthquakes

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that were located in the region

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over the course of a two-day period.

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There were also an additional 28 earthquakes

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that occurred in this area that's sort

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of near Norris Geyser basin between Norris

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and Mammoth Hot Springs.

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This has been an ongoing area of seismicity

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for the past many months, since at least last summer.

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28 new earthquakes were added to the sequence

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that's been ongoing in this area.

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But otherwise, activity distributed throughout the region

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as it often is with most of the seismicity occurring

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in this belt between Hebgen Lake

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and north-central Yellowstone National Park.

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This is the hotbed of seismicity

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for the region historically.

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Turning now to deformation.

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This is vertical deformation, up and down motion,

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at the White Lake GPS station

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on the east side of the Caldera.

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Each one of these blue circles represents one day of data

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and this time series goes back two years.

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Downward trends indicate subsidence and upward trends

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indicate uplift. The overall trend

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during this time period of course is the subsidence

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that has been ongoing since 2015.

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It's interrupted during the summer months by a pause

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in the subsidence or even a slight amount of uplift

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and that's caused by runoff from snow melt

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that sort of puffs up the ground as the ground

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soaks up that water like a sponge.

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But the overall trend is about two to three centimeters

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per year of subsidence.

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That's about an inch per year of subsidence.

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And you can see after the end of summer 2022

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that continued.

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There are a number of little offsets here in the wintertime

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and that's caused by snow and ice accumulation

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on the antenna, which disrupts the GPS signal a bit.

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If we move over to the western side of the Caldera

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and the Mallard Lake resurgent dome

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this is a GPS site near Old Faithful.

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And that same overall trend is apparent,

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subsidence of about two to three centimeters,

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about an inch or so per year, interrupted

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during the summer months by a small amount of uplift

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or a pause in that subsidence with, of course

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the winter storms.

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At Norris Geyser Basin, we haven't seen much

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in the way of any deformation, up or down motion,

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over the past several months.

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This is the two-year plot at Norris.

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There's the summer uplift, lots of winter storms

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that are manifested as small amounts of subsidence,

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but then really nothing since the end

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of the past summer at the Norris area.

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That's remained steady.

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And finally looking at Steamboat Geyser

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everybody's favorite geyser, the tallest geyser

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in the world.

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This is the temperature record in the geyser outflow.

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We started January with a lot of minor geyser activity,

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that's a lot of this up and down motion here,

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with a major eruption that occurred on January 5th.

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And then the temperature went back down

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to air temperature, of course, right around freezing.

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We saw minor activity pick up in mid-January,

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culminating with a major eruption here on January 28th.

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And then back down to air temperature readings

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as the geyser stopped even having little minor eruptions.

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So two eruptions to start the year with Steamboat.

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I guess that means it's not quite done yet

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putting on a show for visitors to Yellowstone National Park.

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Well, that does it for the monthly update

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for February 1, 2023.

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Remember, if you have any questions at all

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you can feel free to email us anytime

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at yvowebteam, all one word, at usgs.gov.

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Stay safe, stay healthy, stay warm

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and we'll see you next time.

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Bye-bye.

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(mellow music)