Inside USGS, No. 6, Ken Pierce, Heavy Breathing of Yellowstone Caldera

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Dr. Kenneth Pierce studied the geology and geomorphology of the greater Yellowstone area for nearly his entire career with the U.S. Geological Survey. From 1965 to present, Dr. Pierce has mapped glacial deposits, pioneered Quaternary dating techniques, conducted research on the Yellowstone Hot Spot, studied the geothermal areas, explored the geology of archaeological sites around Yellowstone Lake, and led field trips into the Park. In this video, Dr. Pierce discusses his work at Yellowstone Lake and how he was able to detect subtle inflation and deflation (or “heavy breathing”) attributed to the subsurface movement of geothermal fluids. Dr. Pierce also talks about his work advising Montana State University students. 


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Location Taken: Vancouver, WA, US


HEAVY BREATHING OF THE YELLOWSTONE CALDERA TEXT: INSIDE USGS Number 6 Ken Pierce U.S. Geological Survey Heavy Breathing of the Yellowstone Caldera TEXT: Heavy Breathing of the Yellowstone Caldera DR. PIERCE: My name is Ken Pierce, I'm a geologist with the U.S. Geological Survey, actually presently retired and emeritus with the U.S. Geological Survey. And my field of focus-of specialization, is in what's called Quaternary geology and geomorphology. Quaternary geology you might think of it as the time of the ice ages, it's the last few million years, it's the very tag end of geologic time, but it's also the most important part of geologic time because it affects how we live on the Earth and the landscapes around us. The other part of my field of focus is geomorphology, which is the study of the form of the land and that has a lot to do with what geologic processes are acting on the land, why the landscape looks the way it does, what were things that happened in the past, or in the present or in the possible future that relate to the form of the land. TEXT: How would you describe the Yellowstone caldera? DR. PIERCE: The center of Yellowstone is a large caldera and calderas around the world are noted for being restless, various kinds of activity going on including uplift, subsidence, volcanic eruptions, all kinds of things happen. And Yellowstone is no different, it's a restless caldera. GRAPHIC TEXT: Hot Spot Geoid and Swell Map of major geoid anomaly in the western United States. Warmer colors indicate higher altitude anomalies, culminating in red at Yellowstone. Volcanic fields (circles) along the hotspot track are shown with their starting ages. The dashed white circle shows the inferred position of the present hotspot based on a rate of plate movement of 25 km/m.y. The dotted line shows the inferred margin of the Yellowstone hotspot swell. TEXT: Why do you say the Yellowstone caldera is restless? DR. PIERCE: Yellowstone has been deflated and inflated in the last part of Holocene time or what we might call post-glacial time. And one of the things that I've been working on is documenting changes in the Yellowstone caldera through time. Part of the geology of Yellowstone is set up really nice for this. There is Yellowstone Lake and a channel of the Yellowstone River that goes across what is the threshold in the center of the caldera. If the caldera inflates, this makes Yellowstone Lake get higher, if the caldera deflates, this makes Yellowstone Lake get lower. And one of the connections between Yellowstone Lake and this threshold area is a channel of the Yellowstone River. At present, it's acting like a large pool, as an extension of Yellowstone Lake. But in the past, when the caldera subsided, this area has acted as a channel of the active Yellowstone River and it actually was so vigorous it was undercutting its banks, it's acting like a vigorous, normal river. If you go into an area just beyond the threshold of Yellowstone Lake in this pool section of the Yellowstone River and auger down, you go through slack water lake-type deposits, sand deposits and then you go into a gravel, indicating the river was very active at that time. If we use these same cores to date the time that the Yellowstone River was acting like a river instead of a pool, we find that this was about 3,000 years ago. So 3,000 years ago, Yellowstone was deflated, and now it has inflated. And this process of deflation, inflation I call heavy breathing of the Yellowstone caldera because it's a big process. The actual volume of material involved is quite large. TEXT IN GRAPHIC TEXT: Elevation of Yellowstone shorelines (S) near Fishing Bridge from 14,000 years ago to present. Transgression indicates a rise in lake levels, resulting in slack water in the outlet reach. As lake levels subside, the Yellowstone River re-establishes its channel. The historic pattern shows inflation and deflation. Ages are in thousands of years (ka) from radiocarbon dating of projectile points (indicating human occupation on the shoreline) and other geologic relationships. TEXT IN GRAHIC: LiDAR (Light Detection and Ranging) showing the outlet reach of the Yellowstone River from Fishing Bridge to Le Hardys Rapids. Although the river is now essentially a continuous, low-velocity pool in the outlet reach, steep, high cutbanks on the outsides of the meanders indicate that the older more sinuous channel contained an energetic river. The dotted lines are old shorelines. TEXT: Is there a pattern to the inflation and deflation? DR. PIERCE: One of the people who surveyed Yellowstone is Dan Dzurisin. And he has shown that both the caldera when it inflates, it swells up, and when it deflates, it's a mirror image of the inflation. So that we know that in the short term, the pattern has been very, very symmetrical - inflation and deflation, which again, suggests some symmetrical process. TEXT: What do you think causes the caldera to inflate and deflate? DR. PIERCE: Whether this is actually the intrusion of magma that somehow is subsiding after that or some process related to geothermal features such as inflation above a geothermal seal - a breaking of the geothermal seal and subsidence as the hot fluids escape, is part of process. TEXT: Could it be magma? DR. PIERCE: If an intrusion of a magma is thought to be the process, it inflates. Then how do you get the deflation? You can't stuff the magma back down the hole it came up. It's going to stay where it is. It's more likely that if magmas are coming in, it keeps uplifting, maybe pausing with uplift. One other thing that we can tell from Yellowstone, is that instead of inflating and then inflating and then inflating, we can tell that this didn't happen because shorelines of Yellowstone Lake are very close to horizontal. So whatever the process of inflation and deflation is, it's not resulting in a net uplift of the center of the Yellowstone caldera. The most likely cause for that kind of thing is geothermal fluids which can come into the system, escape out the sides of system, come into the system again and escape out to the side. TEXT: The research gives us a better understanding of Yellowstone. When did you join the USGS? DR. PIERCE: I started with the U.S. Geological Survey in Kentucky where I was mapping the Ohio River deposits for the U.S. Geological Survey's effort to map the entire State of Kentucky in detail. After I had been there for about two years, I got a phone call saying how would you like to come up to Denver and work on the geology of Yellowstone? And we'll give you a week to think this over. And I said, I don't need a week to think it over, I'm really ready to go. TEXT: How did you get involved with Montana State University? DR. PIERCE: When I was in graduate school, I thought that I would go into teaching because that's the main exposure that I had to other geologists - the professors. I started with the Geological Survey thinking, indeed, I'm going to get some research done and then I'll be better qualified for a teaching position. Well, it never worked out that I went into teaching. I moved up to Bozeman, Montana, with the U.S. Geological Survey in 2000. And since I've been here, I've been affiliate faculty with the Department of Earth Sciences at Montana State. And I really enjoyed being able to work with graduate students, to give lectures, to lead field trips at Montana State. It's very rewarding for me to be able to interact with students. Many have graduated and gone into good careers in geology. And it is very rewarding to be part of that story. DR. PIERCE: We're actually standing on a small alluvial fan. The stream came out of the mountainside there and when it got to this flat floor valley it built a small alluvial fan. Alluvial fans are one of the easiest things to recognize in the landscape because they are conical shape; they occur where a steep stream course gets to a flatter place. And they have this conical fan shape. My daughter is also a geologist. She's at Boise State, and she and her students were studying alluvial fans and they formed an alluvial fan club. TEXT: Special thanks to Students of Montana State University Linda Pierce Jake Lowenstern Images of Yellowstone and Tetons by Dan and Lin Dzurisin Video by Liz Westby TEXT: Interview with Ken Pierce Produced by Liz Westby 2016 TEXT: For more information on Yellowstone visit the Yellowstone Volcano Observatory USGS