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Tourists May Have Influenced Changing Colors of Yellowstone's Hot Springs, Research Says

Throughout decades of admiration by millions at Yellowstone National Park, researchers now say that tourists may be a contributing factor to the visible rainbow-effect of the famed hot springs.

Researchers have formed a model that depicts the colors of the famous hot springs dating back to the 1800s when the area was seldom visited. As Yellowstone grew in popularity and tourists began flocking to the park, certain behaviors changed the makeup of the natural springs.

Starting in the 1940s, colors began to change according to Researchers at Montana State University and Brandenburg University of Applied Sciences in Germany.

"An accumulation of coins, trash and rocks over the intervening decades has partially obscured the underwater vent," researchers wrote.

The addition of outside material lowered the springs' temperature, which altered the natural color.

For decades, tourists have tossed coins into the springs as a luck-fulfilling act. Combined with trash and other debris, such objects have turned spring appearances more colorful.

As tourist traffic increased, researchers linked the fall in pool temperatures to the rise of visitors.

Yellowstone visitation numbers dramatically increased in the late 1940s to near 1 million annual visitors. From then, the influx steadily inclined, surpassing the 3-million mark in 1992.

For the renowned Morning Glory Pool, one of the park's most celebrated hot springs, researchers found that colors have shifted from a deep, uniform blue in the 1800s to a current blend of orange and yellow infusing in the water.

Researchers were able to use light technology to fashion a model that simulated temperature and color changes in pools to reproduce the optical characteristics of the hot springs. Temperatures were notable higher before the 1940s when visitor numbers were lower.