Have You Heard Of The Glowing Blue Ice River That Winds Down An Active Volcano Under Moonlight

A group of casual backcountry campers captured the never-before-widely-documented natural wonder last autumn, linking a rare quirk of glacial geology to faint astronomical activity that most people never notice in their daily lives

Last September, four 20-something office workers based in Reykjavik planned a casual weekend backcountry trip, hoping to catch a glimpse of the mild early-season auroras that often drift across southern Iceland’s highland skies in early fall. They took a slightly wrong turn away from their planned campground after heavy fog rolled in, and set up their tents on a flat patch of mossy tundra at the edge of Eyjafjallajokull, the famous active volcano that disrupted global air travel for weeks back in 2010. Around 2 a.m. that night, one of the campers stepped out of his tent to refill his water bottle, and froze mid-step when he noticed his shadow glowing faint pale blue against the ground. He called the rest of the group out, and all four of them stood staring at the 7-kilometer stretch of clear ice winding down the volcano’s lower slope, the whole river glowing with a soft, even blue light that did not flicker or shift the way auroras always do. They assumed at first that a nearby film crew had set up hidden stage lights, but they waited for three full hours and did not spot a single other person, car or drone anywhere within their line of sight.

Regional geology societies looked over the footage the group shared on a local hiking social media group a few days later, and worked out the perfect overlap of small, common natural events that aligned to create the rare glowing effect. For the past two years, low intensity geothermal activity under the Eyjafjallajokull ice cap has been steadily melting small pockets of glacial ice deep under the surface, and the melt water that flows out onto the lower slope carries an unusually high concentration of microscopically small volcanic glass particles and trapped air bubbles that never get filtered out by the gravel layers under normal rivers. The week the campers visited happened to fall right on the full moon at lunar perigee, when the moon hangs 14 percent larger in the sky and casts twice as much cool, pale blue light on the ground than an average full moon. On top of that, a gentle low energy solar wind stream brushed against Earth’s upper atmosphere that exact night, creating an extremely faint spread of upper atmospheric glow that was far too dim to register as a visible aurora, but just bright enough to add the tiny extra boost of blue light the suspended particles in the ice river needed to shine under the lunar light.

Word of the glowing ice river spread fast through Iceland’s local hiking communities, and local small tour operators rolled out dedicated guided day hike routes within two weeks of the original footage going viral. Unlike multi-day glacier hiking trips that require specialized ice climbing gear and weeks of advance physical preparation, the new routes take visitors up a wide, well packed gravel trail that runs for only 2.3 kilometers from the main paved highland road, and ends at a raised viewing platform that sits 30 meters away from the ice river, so no one has to risk stepping on slippery, unmarked ice to get a clear view. Travelers who have already visited the spot say the experience feels far more immersive than standard aurora chasing trips, because instead of staring up at a moving light show hundreds of kilometers above their heads, they can reach out and touch the glowing surface of the ice, and even dip their fingers in the cold running water that glows faintly blue around their fingertips. Many of the first visitors said the photos they took at the site required zero filters or editing, and immediately became the most shared posts on their personal social media pages.

The viral story has also encouraged a wave of casual local astronomy and geology fans to start looking for similar small overlapping natural phenomena in their own home regions, instead of planning expensive, time consuming trips to chase far away famous natural wonders. Small groups of amateur explorers in the United Kingdom, northern Canada and even parts of northern China have already posted clips of faint glowing blue water streams near old volcanic sites and post industrial glass sand mining areas, where moonlight bouncing off suspended tiny glass particles creates similar mild glowing effects. Many of these small local phenomena only show up for two or three nights a year during a full moon that lines up with low energy solar wind activity, so no one had bothered to document or share them online before, even though they are often located less than an hour’s drive from major urban areas.

Iceland’s local regional tourism board released a short public notice last month, reminding visitors to stick to the marked viewing platform and avoid stepping out onto the ice river surface no matter how solid it looks, as hidden melt water tunnels under the ice can open up without warning even on sections that look perfectly flat and safe. The glowing effect is projected to remain visible on all full moon nights for the next three months, as the low intensity geothermal activity under the volcano shows no sign of slowing down, and regular mild low energy solar wind streams are expected to hit the upper atmosphere through the rest of the local winter. Visitors do not need to book expensive special guided tours months in advance to see the sight, they only need to check the local full moon forecast, pack a set of thick waterproof winter boots and a warm winter jacket, and drive out to the marked viewing spot a few hours after sunset.