The Firehole River

There have been hundreds, or perhaps thousands, of archaeology projects done in the national parks of the United States. A number of these focus on the sites of hotels or other locations that came about as a result of tourists visiting the area after the establishment of the park. The Marshall/Firehole Hotel Project is unique, however, in that it's the only project of its type to focus on the underwater environment. The Firehole River is a particularly strange environment due to the thermal activity of the nearby hot springs, which of course was one of the many sights visitors flocked to Yellowstone to see in the first place.

Near the Marshall Hotel site the Firehole River is shallow, not more than two feet (0.6m) deep in most places. The river got its name from early trappers in the area, who believed that the steam rising from thermal vents was smoke from underground fires. They commonly referred to a small mountain valley like that in Yellowstone as a "hole," so the stream running through the valley came to be known as the Firehole River. The river begins as a series of small, cold water springs. During its 27-mile (44km) course to the point where it flows into the Madison River, however, the Firehole River is fed by hot water from the Upper, Middle and Lower Geyser Basins. This influx of water not only increases the volume of the Firehole, but also dramatically increases the river's temperature and mineral content. The runoff from the thermal geyser basins that ends up in the Firehole River was a high concentration of salts, usually sodium and potassium chlorides. The runoff may also contain may contain high concentrations of sulfate, bicarbonate, fluoride, ammonia, arsenic, lithium, rubidium, cesium, and boric acid.

The Firehole River is a good example of a "thermally polluted" river, although one that occurs entirely by natural processes. The inflow of water from the geysers basins raises the temperature of the Firehole River by 18-47° F (10 to 26° C). It's been estimated that in runoff from the Upper Geyser Basin alone, the Firehole gets some 68 tons (62 metric tons) of minerals every day. The Firehole River contains very large amounts of chloride, fluorine, arsenic, silica and tungsten compared with other streams not affected by thermal input.

The shoes worn by crew members in the Firehole River could not be worn elsewhere in the park, and had to be thrown away at the end of the project.

While it might seem that nothing could survive long in this noxious brew, the rivers in Yellowstone are full of native species, and fishing (under catch-and-release rules) remains a popular activity within the park. One particular non-native species, however, has caused  major headaches for park staff. The New Zealand mud snail (Potamopyrgus antipodarum), first discovered in the Madison River in 1994, has exploded throughout waterways in the park, including the Firehole and lower Gibbon Rivers. Although the long-term effects of the invasive snail population are unknown, many fear that it will wipe out native species by both physically displacing some species and diminishing the food sources relied upon by others.

The mud snail problem is compounded by the fact that the critters are hard to get rid of. They can survive both high and low temperatures, and can even survive in an open-air atmosphere. They are very small, only a few millimeters long, and can easily hitch a ride on people who've been swimming or fishing in the river. Because of this, the Marshall/Firehole Hotel Project field crew was obliged not to wear their work shoes elsewhere in the park, and to dispose of the shoes at the end of the project, for fear of inadvertently carrying mud snails outside the confines of the park.