NPS warns of dangers at Mt. Rainier ice caves after viral 'rainbow ice' photo

Ice caves turn brilliant colors near Mt. Rainier. (Mathew Nichols Photography)

The National Parks Service has issued an advisory to visitors who may be wanting to visit the ice caves at Mount Rainier National Park after a photographer's "rainbow" ice cave photos went viral.

The photos, taken by Mathew Nichols, are taken from the inside of one of the ice caves at the national park, showing a melt-water channel running underneath the summer snow. 

A local geologist who is familiar with the caves told Nichols the variety of colors was due to multiple lighting effects being in play. The reddish colors in the photo – referred to as "watermelon snow," could be related to red-colored algae growing on the snow.

Meanwhile, the blues, greens and purples are from the ice crystals absorbing the reddish parts of the sunlight's spectrum – a process known as Rayleigh scattering. The variable thickness of the snow and the presence of dust and dirt particles trapped in the snow bank contribute to the range of colors. 

Ice caves turn brilliant colors near Mt. Rainier. (Mathew Nichols Photography)

As beautiful as the sight was, NPS officials strongly discourage visitors from approaching or entering ice caves.

Officials say the ice caves are prone to spontaneous collapse due to melting, which is accelerated at this time of year. 

"Collapse, or ice and rock fall could be fatal or cause serious injuries to those who venture inside or near the entrance. Those entering these channels/caves are in danger of hypothermia due to the combination of cold air temperatures inside and colder melt water flowing from the snowfield. Melt water volumes inside will increase throughout the day (just as stream crossing hazards are greater in the afternoon)," officials wrote. 

Mount Rainier National Park was known for a few well-developed ice caves, but with the warming climate, those became unstable and dangerous areas. 

The park closed the 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, park officials said. 

In 2010, an 11-year-old girl was killed during an ice cave collapse at nearby Mt. Baker, while another person died and five others were injured in an ice cave collapse in the Cascades in 2015.