Where the Bison Roam
Act 1, Scene 4, Page 30 of 47
I’m afraid so. The bison were lying on their sides with their feet perpendicular to their bodies. This unusual positioning indicates that they died together and very quickly. The bison were found in a snow-free ground depression near multiple geothermal gas vents in the Pocket Basin. It’s likely the animals had been grazing.
During the following investigation, we learned that the bison had died from a rare combination of events. We think the extreme cold weather caused the steam and toxic gases of the geyser basin to remain close to the ground.
Hydrogen sulfide and carbon dioxide can accumulate in topographically low areas on cold, still nights because the gases are denser than the surrounding air.
When we measured the level of hydrogen sulfide gas in some vents, we found it was far above the safe limits for humans or other animals.
geothermal—having to do with heat from the Earth
hydrogen sulfide—a poisonous gas composed of hydrogen and sulfur and having a rotten egg smell
carbon dioxide—a colorless, odorless gas, formed during respiration, combustion, and organic decomposition
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