'Magical' Ice Caves That Display Rainbow of Colors May Be Deadly

A nature photographer shared an astonishing photo showing the rainbow colors that shone throughout the inside of an ice cave at Mount Rainier National Park in August, but the National Park Service (NPS) recently issued a warning about the dangers of exploring these caves.

"When the sun hits the outside of these caves at Mt Rainier just right, they turn into rainbow ice caves," read the caption of Mathew Nichols' photo on Instagram. "I could not believe my eyes. I went up to Mt Rainier specifically to explore the ice caves and never imagined they would be so COLORFUL."

While a dazzling sight to behold, officials with the NPS said the photo showed a melt-water channel that ran beneath a perennial snowfield, which is snow that does not melt in the summer. This channel can be dangerous to visitors.

"Officials strongly discourage visitors from approaching or entering ice caves or melt water channels as they are prone to spontaneous collapse due to melting, which is accelerated this time of year," a release issued by the NPS said. "Collapse, or ice and rock fall could be fatal or cause serious injuries to those who venture inside or near the entrance."

Although the national park was once home to several ice caves, they've since disappeared because of the warming climate, officials with the NPS said. Today, there are only transitory and unstable channels and caves.

"The park closed the historic ice caves around 1980 due to unsafe conditions including ice chunks and flakes, some the size of a small car, breaking loose and falling from the cave ceiling," the NPS said.

In addition to the dangers associated with falling objects, visitors are also warned they may be in danger of hypothermia because of the combination of cold air temperatures in the cave and the colder melt-water from the snowfield.

The agency encouraged visitors to consider the dangers of exploring an ice cave.

In the photo that Nichols shared, waves of green, blue, purple and orange streaked the top of the cave. He said he did not enhance the colors in the picture, and the colors lasted about two hours before they began to diminish.

"This was by far one of the most magical things I have ever witnessed," his caption said. "Even though it was very cold exploring these ice caves I did not want it to end!"

Patti Wold, an interpretive media specialist for Mount Rainier National Park, told Newsweek in an email that a park's physical science technician researched why the colors appeared in the caves.

Algae growing on the snow may explain the red. The blues and purples may appear because ice crystals absorb the red part of the visible light spectrum, and blue light is the only wavelength that reached the camera lens.

The snow thickness on the cave's roof and any dust in the snow can explain the range of blues, greens and purples.

"The dust is composed of tiny mineral fragments which may produce additional light scattering effects," Wold said.

Wold said visitors are cautioned against visiting the caves year-round, even if they are accessible.

"Due to the risk of rock and ice fall while these channels are exposed, there is no safe place to explore them," she said.

Newsweek reached out to Mathew Nichols for further comment.

These ice caves are far from the only threat to visitors at America's national parks.

In August, a park employee at Yellowstone National Park discovered the remains of a person in a hot spring.

Officials with Yellowstone National Park shared with Newsweek that bison injured more people in the park than any other animal, but visitors should also remain alert for grizzly bears, black bears and moose.

Yellowstone National Park temporarily shut down due to heavy flooding earlier this summer.

Update 9/15/22, 9:58 a.m. ET: This story was updated with comment from Mount Rainier National Park.