The debris thrown into the pools block the magma vents that heat them, lowering the temperature and allowing microbes to thrive.
Those brilliant hues of yellow and orange and green you see when you visit the geothermal pools of Yellowstone National Park didn’t always look that way.
When the park was established back in 1872, the pools actually appeared to be a deep blue color, but due to many decades of tourists throwing trash and other debris into the pools, they now take on a much different look, according to new research as quoted by a Weather.com report.
Scientists at Montana State University used a mathematical model to analyze measurements of geothermal pools across Yellowstone in order to determine what they might have looked like before the arrival of humans. In particularly, they look at Morning Glory, which was likely a clear, brilliant ble before the park became a tourist attraction.
Why the change in color? Pools like Morning Glory are magnets for tourists who want to toss in a coin as if it were a wishing well. They also toss in trash and other debris, such as large rocks. All of this builds up in the bottom of the pool, partially blocking the magma vents that keep the pool heated.
The result is that the temperature of the pool has dropped over the years, now reaching temperatures as low as 140 degrees. This has allowed tiny microbes to thrive in pools they couldn’t survive in before because temperatures were typically in excess of 180 degrees. What you’re seeing when you see the different colors are “mats” are various microbe species. Each color represents a different group of what are known as thermophiles, or heat-loving bacteria that coalesce on rocks depending on the water temperature.
The study used a model that allowed researchers to predict exactly what color the shallower depths of the pool would’ve appeared to visitors before the change in temperature when Morning Glory was much too hot to host the microbes.
A visitor today could probably get an idea of what it would look like by looking at the deepest part of the pool, which retains its dark blue color because it is deep enough to scatter the light in the water, even though it is likely covered with a yellow mat.
One survey conducted in the area in 1871 said of the springs that nothing conceived by humans “could equal the peculiar vividness and delicacy of color of these remarkable prismatic springs.”
Yellowstone National Park is famous for its geothermal activity, as it sits on the site of basically a massive volcano that scientists believe will erupt catastrophically at some point in the future. Its most famous feature is a geyser known as “Old Faithful,” but its numerous hot springs, mud pots, and fumaroles draw many tourists each year. There are about 10,000 thermal features in the park.
Yellowstone National Park is primarily located in the state of Wyoming, but it extends into Montana and Idaho. Congress established it as a park in 1872, and President Ulysses S. Grant signed it into law. Besides its geothermal features, it is known for its wildlife.
Scientists believe that Native Americans have lived in the region for 11,000 years. The famous Lewis and Clark Expedition bypassed the park in the early 1800s, and organized exploration didn’t begin until just a few years before it was declared a park.
The park spans 3,468.4 square miles and includes canyons, rivers, mountain ranges, and lakes. Yellowstone Lake, one of the largest lakes in North America at a high altitude, sits on the Yellowstone Caldera, a huge supervolcano that could be a ticking time bomb for the continent. It is so large that half of the world’s geothermal features are located in Yellowstone.