Yellowstone's famous Morning Glory Pool used to be a deep blue color. Today it's mostly green with a yellow rim. Why has the color changed? A recent report published in Applied Optics cites that humans are the reason for the change.
"As a result of coins, trash, and rocks thrown into the pool over time, the vent has become partially blocked, leading to a lower temperature and altered color pattern," wrote the study's authors, Nugent, Shaw, and Vollmer.
The pool that explorers encountered in the 1800's was probably hotter than today based on the description of the color.
"In the case of Morning Glory Pool, they were even able to simulate what the pool once looked like between the 1880’s and 1940’s, when its temperatures were significantly higher."
Even photos taken as recently as 1966 show a bluer color than today's pool. (See related article: Things Stuffed Down Yellowstone's Geysers)
The study was initially about optics and imaging. After the imaging technic was applied to Yellowstone's colorful pools, the study became more about biology. The authors hope to collaborate with biologists studying the thermal features in Yellowstone in the future.