Photos of a rainbow-hued world inside an ice cave on the flank of Mount Rainier have prompted the National Park Service to issue a warning about entering the sometimes treacherous maws.
Nature photographer Mathew Nichols posted the pictures to Instagram and other social media. They show red, blue and green colored ice. Nichols said he did not enhance the colors in the photos.
"I could not believe my eyes," Nichols said. The phenomenon lasted two hours before fading.
Ice absorbs red light more readily than blue, which often gives glaciers and ice fields a brilliant cyan color.
The red coloring might come from watermelon snow — a type of algae that blooms on snow fields in the summer. Despite the tempting name it has nothing to do with fruit and is considered toxic to people.
"This was by far one of the most magical things I have ever witnessed," Nichols said.
Warning
Popular photos on social media often lead others to attempt to capture the same image. Sometimes, that can lead to dangerous situations.
On Friday, the Park Service issued a media advisory on the dangers associated with Rainier's ice caves.
"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," the Park Service said. "Collapse, or ice and rock fall could be fatal or cause serious injuries to those who venture inside or near the entrance."
In 2015, an ice cave collapsed in the Mount Baker-Snoqualmie National Forest, killing one and injuring four others. In 2010, an 11-year-old girl died when struck by an ice boulder near the same caves, known as Big Four Ice Caves.
In addition to collapse, the air temperature inside an ice cave can be considerably colder than outside air, the Park Service said. Hypothermia can result.
Ice cave history
Mount Rainier was once known for its well-developed ice cave system, the Park Service said. Those melted away due to a warming climate. Now, ice caves are seasonal and more unstable.
The park closed the ice caves to the public in 1980 in order to protect visitors.
In 1978, the Paradise Ice Caves had a length of eight miles, according to Caving International magazine.
