The Morning Glory pool in Yellowstone National Park. Source: Getty Images
IT’S an incredible, otherworldly sight that lures thousands of visitors every year.
But the Morning Glory hot spring in Yellowstone National Park, US, didn’t always look as it does today.
That’s because tourists have been throwing coins, rocks and rubbish into it over the past 75 years. The accumulation of filth changed the appearance of the water from a deep blue to a sickly yellow/green colour.
So how did it do this? The objects clogged up an underwater vent which then caused the water temperature to cool, allowing pigmented bacteria to thrive. The bacteria are what gives the spring its extreme colours.
That’s according to researchers from Montana State University and Germany’s Brandenburg University of Applied Sciences whose study has been published in the journal Applied Optics.
While the effect of the vandalism has been known about for years — in 2009 a sign was placed next to the pool warning that it’s “fading” due to the rubbish — the researchers analysed the forces behind the drastic change.
This photo, which was taken in 1966, shows what it used to look like:
This photo was taken decades ago. Picture: William Keller/National Park Service Source: Supplied
As does this holiday snap, which was taken back in 1958.
A visit to Morning Glory. Picture: Don Pugh Source: Flickr
And this is it now, quite a difference:
It’s like a giant blob. Picture: David Fulmer Source: Flickr
Let’s look a little closer:
Eww ... Picture: Martin Bravenboer Source: Flickr
The research began quite lightheartedly, according to Michael Vollmer from Montana State University who said: “When we started the study, it was clear we were just doing it for fun.”
Colleague Joseph Shaw said they were almost out of their depth on the issue, at first: “We didn’t start this project as experts on thermal pools. We started this project as experts on optical phenomena and imaging, and so we had a lot to learn.”
However, they quickly discovered there was very little scientific literature on the topic. So they started by taking measurements of the pool using handheld spectrometers, digital SLR cameras for visible images and long wave infra-red thermal imaging cameras for non-contact measurement of the water temperatures.
Using the data, along with previously available information about the physical dimensions of the pools, they created a one-dimensional model taking into account different conditions such as lighting and microbes on the surface of the water.
Essentially, they simulated what the pool once looked like between the 1880s and 1940s, when its temperatures were significantly higher. They found that the pool’s colours are formed by physical, chemical and optical variables.
Here are some of their renderings showing the colour change:
Before. Picture: Paul W. Nugent, Joseph A. Shaw, and Michael Vollmer Source: Supplied
And now. Picture: Picture: Paul W. Nugent, Joseph A. Shaw, and Michael Vollmer Source: Supplied
This excerpt from the study explains the study further: “An accumulation of coins, trash and rocks over the intervening decades has partially obscured the underwater vent, lowering the pool’s overall temperature and shifting its appearance to a terrace of orange-yellow-green. This change from blue was demonstrated to result from the change in composition of the microbial mats, as a result of the lower water temperature.
“A general relationship between shallow water temperature (hence microbial mat composition) and observed colours was confirmed in this study. However, colour patterns observed in deeper segments of the pool are caused more by absorption and scattering of light in the water.
“These characteristics — mats having greater effect on colour in shallow water, and absorption and scattering winning out in the deeper areas — are consistent across all the measured pools.”
Although it’s sadly being polluted, it’s still an incredible sight. If you visit, please think twice before throwing anthing in there!
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