The beautiful, yet deadly, hydrothermal features of Yellowstone National Park are best admired from afar, yet some animals may misstep. Over the years, a handful of animals have made costly mistakes around hot springs and landed themselves in situations that often end up fatal.
One such incident occurred on Saturday, June 21, when a bison perished after stumbling into Grand Prismatic Spring — while the hot spring’s rainbow colors may look inviting, its water is nearly boiling at 192 degrees Fahrenheit (89 °C). Although accidental animal deaths at hot springs are rare, they always serve as a morbid reminder that one wrong step could lead to an agonizing fate.
A Deadly Accident at Yellowstone
The bison that fell into Grand Prismatic Spring reportedly slipped into the hot water and fell further in as it tried to escape. Yellowstone park officials deemed it too dangerous and destructive to retrieve the carcass, which will break down until only bones remain.
This isn’t the first time an animal has fallen victim to Yellowstone’s hydrothermal features; an elk calf died some years back as it tried to get free from mud pots in West Thumb Geyser Basin. Bones from diseased animals have also been found at other hot springs like Gentian Pool, Ojo Caliente, and a spot known as “Skeleton Pool.”
At least 22 humans have also died due to scalding after falling into a hydrothermal feature at Yellowstone, and hundreds of injuries have also been reported. This means that hot springs have accounted for more deaths than wildlife at the park, since eight people have died from bear encounters and two people have died from bison encounters.
Read More: Microbes in Yellowstone Thermal Pools Could Shed Light on Ancient Life
Are Hot Springs Acidic?
The hot springs at Yellowstone are extremely dangerous, but they’re not exactly equivalent to vats of corrosive acid as many people would believe. According to the USGS, most major springs and geysers in Yellowstone — including Old Faithful and Grand Prismatic Spring — are neutral (pH of around 7) or alkaline/basic (pH greater than 7).
For reference, pure water is neutral at 7 pH. The acidic end of the scale includes stomach acid (around 1 pH) and battery acid (around 0.8 pH), while the basic end includes bleach (around 11 to 13 pH) and lye/caustic soda (around 14 pH).
Not all hydrothermal features at Yellowstone are the same, either. While many of the popular hot springs and geysers are closer to neutral or alkaline, other features are notably more acidic, including fumaroles (gas vents) and mud pots. The acidity of these features is tied to the buildup of acid-sulfate fluids or gases that originate from steam.
Steam usually takes a different path than superheated alkaline-chloride fluids as it rises from underground, separating along with gases like carbon dioxide and hydrogen sulfide. When these gases reach the surface, they interact with the air and groundwater to form carbonic acid and sulfuric acid, creating a low pH environment that can alter surrounding rocks and surface sediment.
Boiling Water and Toxic Gases
The primary danger of hot springs at Yellowstone is actually related to the high temperatures rather than acidity. In the rare instance that an animal falls into a hot spring with similar conditions to Grand Prismatic Spring, its death comes from being nearly boiled alive.
However, groups of animals have also died from exposure to high concentrations of toxic gases. In one mysterious case from 1897, a geologist came across eight dead bears at a region of the park called “Death Gulch”. Over a century later, in 2004, park officials found five dead bison in Norris Geyser Basin.
Both events were likely caused by hydrogen sulfide and carbon dioxide from nearby gas vents. In the 2004 case, the gases may have drained downhill and accumulated where the bison were located.
Whether they take an unfortunate misstep at a hot spring or have an unlucky encounter with toxic gases, even Yellowstone’s majestic fauna aren’t entirely safe in America’s oldest national park.
Read More: New Hydrothermal Feature Emerges at Yellowstone National Park
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
USGS. Which is More Dangerous to Yellowstone visitors, wildlife or hotsprings?
USGS. Where did Acid Sulfate Hot Springs Come From and why are They Important?
USGS. Volcano Watch — What did kill those bears and bison at Yellowstone?
NPS. Geologic Overview of a Bison-Carcass Site at Norris Geyser Basin
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
