Water levels at Yellowstone Lake in Wyoming dropped 11 feet between Sept. 26 and 27, 2026.
In September 2026, a rumor (archived) circulated online that water levels in Wyoming’s Yellowstone Lake dropped 11 feet between Sept. 26 and 27.
For example, a Facebook user wrote on Sept. 29:
YELLOWSTONE NATIONAL PARK – Scientists are investigating after portions of Yellowstone Lake reportedly dropped nearly 11 feet overnight when an unknown underground channel opened beneath the lake bed.
Rangers first noticed the change Sunday morning after several docks were found sitting completely above the waterline. Geologists believe shifting rock beneath the lake may have opened a previously sealed underground passage, allowing millions of gallons of water to drain into Yellowstone’s extensive subterranean geological system.
The rumor also spread on X and Threads (archived, archived).
The rumor originated from the Facebook page Casper Planet, which described its content as satire. The page’s About section read, “Snews that doesn’t matter directly to your Snews feed. Did we say this is satire? Well it is, names/locations are made up.”
In addition to Casper Planet’s own declaration of the satirical nature of its content, we found no reporting from reputable sources on Google, Yahoo or DuckDuckGo (archived, archived, archived) that supported the Facebook page’s claim about Yellowstone or cited the “geologist Dr. Aaron Keller” who featured in Casper Planet’s post.
The image that Casper Planet used to illustrate the satirical story was fake. The highly regarded Pangram artificial intelligence detection tool found the image to be “fully AI.” Open AI’s Verify scanner found that someone had generated the image using Open AI’s tools.
Though Casper Planet did note on its page that its content was satire, it did not say so on the actual post. Shares of Casper Planet’s posts on X and Threads contained no indications (aside from the nature of the content) that the story was satire.
The United States Geological Survey’s water level readings from the Yellowstone River at its inlet into Lake Yellowstone did not show an 11-foot drop in water levels between Sept. 26 and 27. The USGS found that water levels between 9 a.m. on Sept. 26 and 9 a.m. on Sept. 27 varied by inches, not feet.
Snopes has previously investigated other satire claims shared by Casper Planet, including whether an ancient city appeared under Wyoming’s Horse Peak Mountain or whether Wyoming wolves mauled a Colorado man who tried to join their pack.
Since the effectiveness of satire is subjective, we use “originated as satire” or “labeled satire” ratings based on creators’ description of their work. It’s your call on whether you agree.
