Lisa A. Morgan

In preparation for a trip to Yellowstone. This is a collection of USGS papers from the late 1990s early 2000s; although not explicitly described so, it’s kind of a festschrift for a couple of long-time Yellowstone geologists, John Love and Irving Friedman. I was initially surprised and a little disappointed because there is very little volcanology or structural geology discussed; instead almost all the papers are on environmental geochemistry and remote sensing. Still, I happen to know a little about environmental geochemistry; hence some of the data presented was pretty intriguing.


The initial paper, “The Yellowstone Hotspot, Greater Yellowstone Ecosystem, and Human Geography”, is a fascinating introduction to how Yellowstone geology affects everything else in the area. If you’ve been through Yellowstone, you’ve probably noted large areas of rather boring monocultures of lodgepole pine (if you happened to be there in 1988, you also probably noticed that most of that lodgepole pine was on fire). Lodgepole pine has much lower nutritional and water requirements than other tree species that could potentially grow in the Yellowstone climate; lodgepole can grow on rhyolite soils, which are nutrient-poor and well-drained; and rhyolite soils are what you get a lot of in a caldera eruption. Areas of the park with older Tertiary volcanic soils or younger glacial lake deposits get a much more diverse flora (and lodgepoles don’t grow there because they are shade-intolerant as saplings and can’t sprout if they are shaded out by other trees or underbrush. On an even larger scale, the whole Yellowstone area climate is controlled by the hotspot; the doming creates an area of orographic precipitation on the upwind side and a rain shadow on the other.


After a paper on a supposed landslide block dated by dendrochronology and one on ancestral Yellowstone Lake, the next paper is about reconnaissance of the floor of Yellowstone Lake. These studies, using a remote underwater vehicle and imaging sonar, made a lot of the mainstream media when they first came out in. The floor of Yellowstone Lake turns out to have numerous hot springs, plus what are essentially underwater geysers, plus remnants of hydrothermal explosion craters (including the largest hydrothermal crater known). These are similar to what are called maar craters; a maar crater, though, is caused by groundwater contacting magma and flashing to steam (with some sort of confining layer to contain the steam until it builds up enough pressure to explode). In a hydrothermal crater, there’s still obviously magma involved but it’s a lot further down – just like the heat source for the Yellowstone geysers. Thus you have hot water at temperatures well above the atmospheric boiling point again accumulating under a confining layer. Something happens to release the pressure – crack in the confining layer, for example (it was suggested that melting of a Pleistocene ice cover could do this but it couldn’t be tied to the explosion date). Yellowstone hydrothermal water tends to be self-sealing; dissolved silica can deposit into cracks faster than they can propagate. Thus pressures can build up to larger levels than you’d find in areas with other mineralogy.


The next paper discusses the lake “breathing”; water level – at least in the relatively short time it’s been accurately monitored – changes cyclically. The authors conclude, after examining a variety of possibilities, that hydrothermal activity is again responsible; hydrothermal pressure causes the bed of the lake to bow upward and when the pressure is released (not necessarily at the lake, or even at the surface) water levels subside.


The next eight papers discuss surface hydrochemistry; the elemental composition of water entering the lake from below, of water entering the various streams within the park, and the effects of gold mining just outside the park to the northeast. I was interested to see if Yellowstone National Park would meet Clean Water Act standards if it were an industrial facility rather than a national park.


This is a complicated issue; the actual standards involved are promulgated by the State of Wyoming (one of the things I learned from the initial paper was that although parts of the park are in Idaho and Montana, and those states reserve the right to apply their laws if they want to, it’s agreed that Wyoming law applies throughout the park). The Feds have agreed that Wyoming water quality standards are adequate under the CWA. Wyoming regulations also include standards for a variety of organic chemicals, which were not measured by any of the studies in this book, plus a general catchall clause prohibiting discharge of “pollution”, apply different standards to different drainage basins, and note the standards do not apply during periods of “low flow”.

See the full Wyoming standards at
http://water.epa.gov/scitech/swguidance/standards/wqslibrary/upload/2001_04_05_s...
for more than you want to know. Using the data from the book turned out to be somewhat more complicated than I originally expected, as the authors of the most relevant paper (“The Influence of Sublacustrine Hydrothermal Vent Fluids on the Geochemistry of Yellowstone Lake”) expressed their results in molarity (or micromoles, or nanomoles, or picomoles), so I had to add a column for molecular weight to my spreadsheet. These authors also added a table of “Regulatory Limits and Potential Human Health Effects of Certain Elements”, but it’s not terribly useful; the regulation used is the Safe Drinking Water Act, not the Clean Water Act, and since the regulatory limits are expressed in mg/L they aren’t directly comparable to the measured data in mole fractions. In addition, there is little overlap between the elements referenced in Wyoming standards and the ones measured by USGS investigators; the USGS was primarily interested in seeing how much the lake water was influenced by geothermal sources, not in aquatic or human health issues; thus the USGS looked at elements associated with geothermal activity (for example, cesium, rubidium and tungsten) while the State of Wyoming regulates metals like copper, chromium, and beryllium. The only overlap between the regulations and the USGS measurements were for temperature, pH, antimony, arsenic, and mercury; of these, the only measurements that exceeded CWA standards were for water temperature and pH (although a couple of the measurements from underwater hydrothermal vents exceeded SDWA for antimony, which are much lower than the CWA standards). I note none of the papers were concerned with air emissions.


A later paper (“Application of Trace-Element and Stable-Isotope Geochemistry to Wildlife Issues, Yellowstone National Park and Vicinity”) does address health effects of hydrothermal water on wildlife; in this case the element of concern turned out to be fluorine. Plants growing around some of the hot springs pick up fluorine, which then causes fluorosis in elk that forage on the plants – their teeth and jaws weaken and they die prematurely from starvation. The authors speculate that there may be other more subtle interactions with various chemical elements but they don’t cause any obvious acute or chronic effects.


A later paper, “Life Cycle of Gold Deposits Near the Northeast Corner of Yellowstone National Park – Geology, Mining History, Fate”, documents a situation involving gold mines near Cooke City, Montana. The mines were first developed in the late 1800s and were worked on and off until the 1950s; in the 1990s Crown Butte Mines, Inc., used extensive exploratory drilling to find that early miners had missed the main deposit and proposed to mine it. Even though the area is outside the park (it is in a National Forest), environmentalists threw a fit; the Clinton administration directed the Department of the Interior to put the mining permit on hold, and eventually Crown Butte agreed to a settlement that paid them for the exploratory work and opened an equivalent amount of Federal land elsewhere.


The last paper was an interesting account of outflow measurement from the Norris Geyser Basin by the USGS. I generally imagine that government agencies have close to infinite resources at their disposal and that such measurement would be done with sophisticated high-tech equipment; as it turned out, author Irving Friedman backpacked concrete to the site, built a measuring weir, installed a stilling box, and used a homemade float gauge to record data. The float was an empty plastic bottle; measurement was done with a hand-wound potentiometer installed in a second bottle and connected to the float by a long arm. Data was logged and periodically collected. The setup kept leaking, which was kept partially in check by packing the second bottle with silica gel packets. Eventually a modem was setup to allow more or less real-time monitoring, which recorded a couple of high-flow events that otherwise would have been missed because there was nobody around to watch geysers erupt. Friedman passed away before this volume was published and he’s one of the dedicatees.


Like most collected papers, the level of my interest was uneven although all had some worthwhile information. There are pages and pages of data tables, and some pull out maps. As mentioned the first chapter is probably worth the whole cost of the volume.… (mais)