USGS warns of poisonous gas emissions in National Park: Yellowstone toxic gases can kill animals.

YELLOWSTONE volcano is the subject of much speculation over whether there will be a major eruption in the future – but now National Park’s authorities have a more pressing issue to worry about as experts warned of toxic gases venting from the supervolcano.

Yellowstone National Park is home to thousands of hot springs and geysers spewing clouds of mostly harmless, rotten-smelling gases. But in the deeper parts of the Yellowstone wilderness where tourists are told not to stray, toxic fumes of lethal gas are powerful enough to kill.
USGS scientists studying the Yellowstone volcano have warned of the ever-present danger in the latest issue of the weekly Yellowstone Caldera Chronicles.
Dozens of Yellowstone animals have dropped dead over the years as a result of inhaling toxic fumes. The two killers are poisonous levels of carbon dioxide (CO2) and hydrogen sulfide (H2S), which are concentrating around ground levels.
Most of the gases emitted by Yellowstone’s network of hydrothermal pipes are harmless water vapor gases. But hiding in these emissions could be concentrations of toxic gases, which have proven to be lethal to animals.
CO2 is particularly dangerous because it is an odorless and colorless gas. H2S, on the other hand, is easier to spot thanks to its distinctive smell of rotting-eggs but the gas is also colorless and flammable. Both gases typical pool around ground levels because they are heavier than air. This can be absolutely lethal to animal grazing in the parks fields with their noses close to the ground.
In most circumstances, the wind will dilute carbon dioxide and hydrogen sulfide to low concentrations that do not threaten the health of people and animals. However, in certain very stable atmospheric conditions, though, these relatively heavy gases can accumulate in low-lying areas and pose a serious hazard.
In 1897, geologist Thomas Jaggar (who would later go on to found the Hawaii Volcano Observatory) led a field party to visit “Death Gulch”, a small, steep ravine in a remote hot springs area in what is now Yellowstone National Park. Here, the deaths of numerous bears, elk, rodents, and insects had been reported. The group came across eight new bear carcasses during their visit to Death Gulch, and Jaggar surmised that their deaths had been caused by exposure to poisonous levels of carbon dioxide (CO2) and hydrogen sulfide (H2S) gases.
Over a hundred years later, in 2004, five dead bison were discovered in Yellowstone’s Norris Geyser Basin. Strangely, the bison lacked markings on their bodies that would suggest they were attacked by predators. Based on the position of their bodies, it appeared that the animals had died suddenly and as a group. Similar to the events at Death Gulch, park scientists concluded that their deaths were likely caused by a buildup of lethal levels of carbon dioxide and hydrogen sulfide gases at the ground level, where the animals were grazing.
Under most weather conditions, visitors will not be bothered by the gas emissions that are an integral part of Yellowstone’s fascinating hydrothermal areas. However, as recommended by the National Park Service, people should remain aware of potential gas hazards when exploring these areas and leave immediately if feeling sick. Even though there is no record of any human deaths due to exposure to gases at Yellowstone, the lessons of Death Gulch and the Norris bison provide warnings that should be heeded.


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