"Not all eruptions are Armageddon" - Yellowstone Update for March 2021

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Mike Poland, Scientist-in-Charge of the Yellowstone Volcano Observatory, debunks the misconception that if Yellowstone were to erupt, it would be Armageddon. In fact, the most common form of eruptive activity at Yellowstone is a lava flow, and even those aren't that common. They happen only once every few tens of thousands of years. Learn more in this monthly overview of activity at Yellowstone Volcano for March 2021.

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Length: 00:05:23

Location Taken: Vancouver, WA, US

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Hi everybody. I'm Mike Poland, the scientist-in-charge at the Yellowstone Volcano Observatory. This is the monthly update for March 1st of 2021. 

Now, last month we debunked one of the most common misconceptions about Yellowstone. That is that the volcano is somehow overdue. It's not the way it works. And of course the math doesn't work out anyway. 

This month I thought we'd tried to debunk another misconception, and that is that if Yellowstone were to erupt, it would be Armageddon, that only explosive eruptions are possible. And that's just not true. 

In fact, the most common form of activity at Yellowstone is a lava flow, and even those aren't that common. They happen only once every few tens of thousands of years. 

Now, the last big explosive eruption at Yellowstone was 631,000 years ago and resulted in the caldera that you see outlined in red here. Since that time, there have been about 20 or more lava flows that have occurred in the caldera region. 

Now these lava flows are very thick, pasty rhyolite flows, not like what you'd see in Hawaii. Not those very fluid flows. These are very thick flows that don't move very quickly, but they are huge.

And they occurred in two episodes in Yellowstone after the big caldera forming explosion. One was about from the time of the explosion till 250,000 years ago or so. And that gave you these orange [colored] lava flows here, one in the Canyon area and then one over here on the west side of the caldera. 

And then there was a much more voluminous period of lava flow activity from about 170,000 years ago to 70,000 years ago. And that resulted in all the pink [colored] lava flows you see here. The youngest is right down here in the southwest corner of the park, and that's the Pitchstone plateau flow. Now this is a view of Madison Junction looking off to the north. Here's the caldera rim, and these big plateau areas that you see in the foreground are actually these really thick lava flows. They can have flow fronts that are basically cliffs that are 450 feet tall. In fact, if you stand in the Old Faithful area, that's what you're seeing all around you are some of these really great big lava flows. 

And if you want to see into the guts of these lava flows, go to the Grand Canyon of the Yellowstone. This is carved through one of these posts caldera lava flows really exposing this beautiful interior which has been altered by gases and acidic fluids that flow through the area and change the composition of the lava into sort of a clay. It gives it this really spectacular color scheme here. 

So lava flow activity at Yellowstone, much more common, but still not super common. Much more common than explosive eruptions, but still somewhat rare, the last one being about 70,000 years ago. Okay with that, let's get into what happened in Yellowstone during the month of February. 

The University of Utah Seismograph Stations, which is responsible for the operation and maintenance of the Yellowstone seismic network, located just 67 earthquakes during the month of February in Yellowstone. The largest was a magnitude 2.4 over here on the east side of the park. There was also a small swarm of about 20 earthquakes that occurred between February 1st and the 16th near West Yellowstone, Montana. This level of seismicity is pretty much background levels for the region. 

We also haven't seen much in the way of changes in deformation over the past year at Yellowstone. This is from the White Lake GPS station, which is on the east side of the caldera, Sour Creek resurgent dome. Each one of these circles is a day of data. And this shows data from vertical deformation over the last two years. And this downward trend that you're seeing overall means subsidence. The subsidence over this two year period is about five centimeters or so, meaning that we're seeing subsidence at rates of about two to three centimeters per year. 

The same is true on the west side of the caldera, the Mallard Lake resurgent dome. This is a GPS station again, over two years. It's located near Old Faithful. And you can see this overall downward trend of about four centimeters over this past two year period. So about two centimeters per year of subsidence. 

In the Norris area, we haven't seen much deformation over the past year. This is the last two years of vertical deformation at Norris. There was a small antenna change during this time period. So that offset is somewhat artificial. There is perhaps a slight amount of subsidence over the past year or so, but really it's not much to speak of, probably within the error. So no noteworthy deformation of the Norris area. 

And finally looking at everyone's favorite geyser, Steamboat Geyser in the Norris Geyser Basin, there were two eruptions during the month of February. This is the temperature record from Steamboat. Every time there is high temperature, that means there's hot water running through the channel. And these spikes here on February 3rd and again on February 21st indicate major water eruptions. And all of this leading activity is minor eruptive activity at Steamboat. So two eruptions at Steamboat, that brings the total for the year to four eruptions. There haven't been that many eruptions, but that's sort of typical of winter months because groundwater levels are a little lower during the winter than during the summer. So hopefully this picks up in the months to come and gets us ready for another spectacular summer at Yellowstone.

Well, that's it for the March 1st, 2021 update from the Yellowstone Volcano Observatory. 

Now remember, if you have any questions feel free to email us anytime at yvowebteam@usgs.gov

Until next month, stay safe, stay healthy. See you later, take care.