The photo above displays some of the enormous ice crystals and hoarfrost observed on the ceiling of a glacier cave in the Castner Glacier in March of 2020. This cave is an example of a Röthlisberger channel or R-channel. These are channels formed at the base of the glacier by flowing subglacial water, melting a semi-circular tube through the ice. The water flowing through the channel, deep in the glacier, heats the ice from friction. Without this frictional, viscous heating, the channel would close from ice deformation due to the incredible overburden pressure of the ice above.
Near the exit of the channel, warm air in the summer melts the ice further, sometimes leading to large cave entrances like this. It’s highly unlikely that water would ever completely fill this part of the cave. However, further back, sometimes only a few tens of meters, the channel will be full to the ceiling in summer months.
How does all the water get under the glacier to form these channels in the first place? Well, there are quite a few ways. During the melt season, water can drain through the ice surface through crevasses and near-vertical holes called moulins. Much of the water eventually ends up at the glacier bed, where there are a series of linked cavities, channels, and even subglacial lakes. Additionally, water can be present from geothermal activity melting the ice above as well as frictional heating from the motion of the ice along the glacier bed.
Caution always needs to be exercised if approaching or entering any glacier or ice cave. There is quite a bit of overhead danger, as there are often many loose rocks at the top that fall frequently and unexpectedly. In winter, avalanche danger may pose a risk. These caves are usually at the terminus where the ice is often quickly melting and can potentially collapse without warning.
There can also be great danger from glacial lake outburst floods. Water often pools on glacier surfaces and at glacier margins forming lakes. Once the water pressure is high enough, and the subglacial drainage system is ready, these lakes can drain. Sometimes they drain catastrophically in a matter of hours
The video below shows some active moulins, supraglacial streams, and pooling water on the surface of glaciers.
The hoarfrost and giant ice crystals on the ceiling grow from water vapor present in the cave. Their formation requires a unique environment like that present in glacier caves like this. There is a large temperature gradient between the floor of the cave and the ice that drives convection that allows for the deposition of ice from supercooled water vapor on the cold surface of the glacier ice.
Sometimes these crystals grow as hexagonal prisms, with most of the growth occurring at the edges and corners of the crystal. These often develop a hollow cup-shape. This is described as skeletal growth. The photo below shows an area full of skeletal growth patterns with a significant amount of branching.
In another area of the cave, there was a section of chandelier-like long c-axis ice columns that had limited skeletal growth on them. It’s not fully understood what mechanism drives the growth of these spikes, but it is thought that they form much faster than the surrounding skeletal crystals.
Some of the most beautiful ice crystals were in the glacier ice itself. It’s interesting to note that glacier ice is actually considered a metamorphic, mono-mineralic rock, composed of hundreds of millions of ice crystals. The crystals are metamorphosed snow crystals changing under the weight of the snow on top of them. The pressure causes the recrystallization of many snowflakes into larger and denser ice crystals.
The ice we see down here at the glacier terminus formed high up in the accumulation zone. That’s where at least some of the snow remains at the end of the summer before new snow falls on it. On the Castner Glacier, that’s about 15 km (9 miles) from the terminus. The older snow eventually densifies into firn and then into glacier ice. The ice flows down the valley from the force of gravity at a few tens of meters per year, reaching this spot where we get to see it, hundreds of years later.
The below video shows the reflection of the different faces of ice crystals as well as embedded sediment and air bubbles in the glacier ice.
The entrance to a glacier cave at the terminus of the Castner Glacier in the eastern Alaska Range. The ceiling of the cave is covered in fine hoarfrost, with crystals that increased in size further back in the cave.
This is a fairly accessible cave, less than a one-mile approach from the Richardson Highway. But, these formations need to be treated with respect and entered cautiously. Especially now in the melt season, there is talus and numerous rock frequently falling off the top of the entrance, fast-moving water with the potential for outburst floods, and potential collapses of the ceiling itself.
The Pleiades cluster (upper left) shines brightly in the sky with the aurora borealis over Chena Dome. This photo was taken from the Angel Rocks to Chena Hot Springs trail in the Chena River State Recreation Area.
The Pleiades cluster is one of the closest star clusters to Earth (only 445 light-years away), found north-west of the constellation Taurus. It’s also known as the Seven Sisters of Greek mythology and Messier 45 (M45) in astronomical listings. M45 is an open star cluster containing over a thousand stars that are loosely bound by gravity and slowly dispersing over time.
The Pleiades is largely composed of hot B-type stars that formed about 100 million years ago (about 50 times younger than our Sun). Many of these stars are 50-1000 times brighter than the Sun!
The cluster is approximately 35 light-years in diameter, that’s over 200 trillion miles across (over 70,000 times the distance from the Sun to Neptune). All that in that tiny little dust-speck in the sky!
A raggedy looking snowshoe hare slowly gaining its summer coat. They’ll typically keep a bit of white on their flanks, feet, and sometimes ears. Otherwise they turn mostly brown. This one came running straight toward us out of the woods from the side while walking at the Wedgewood Wildlife Sanctuary in Fairbanks yesterday.
Last year we heard about the Shovel Creek Fire on Murphy Dome almost every day. It started on June 21, 2019, from lightning. Many residents were evacuated later in the month when it neared two subdivisions. In town, bulletin boards stood outside the grocery store entrances, updated daily with maps of the current fire-lines and general information. The fire grew to over 23,000 acres in July and wasn’t contained until August. Portions burned until the snow fell.
After our long winter, the snow is almost gone. We explored some of the burn areas last night. This is definitely one of the largest burn areas I’ve seen, stretching as far as I could see down the hill. The landscape was full of charred spruce snags with little tufts of dead, copper-colored needles. Quite a desolate look, with just some hints of green and an occasional live tree somehow missed by the blaze.
Sunlight glimmering off the frozen Savage River in February. Taken at the end of a long day hiking the Savage Alpine Trail and some of the nearby mountains. This is one of my favorite established trails in Denali National Park & Preserve, especially in the off-season before the shuttles start running. It looks to be an interesting year in the Park with the road being closed before Polychrome, and possibly no buses running due to COVID-19. I’m really curious to see what it’s like this summer!
In the short summer, water scours the glacier surface creating a ripple-like surface on the ice going down-glacier. At the end of the season, when the first major snow falls the rough surface becomes once again smooth. This was taken at the end of the day when I could really see the shadows from those ripples. It kind of looks like little waves on the glacier.
McGinnis Peak is an 11,400 ft (3,470 m) tall mountain in the eastern Alaska Range. It rises almost 6,000 feet over the glacier below.
Aurora borealis fills the southern sky from the Granite Tors Trail in the Chena River State Recreation Area. The photo was taken shortly after a corona passed overhead and the band moved to the south. You can still see the giant rays of light as they move off into the distance. More story and photos at the link below.
Gorgeous color fills the sky over the White Mountains from the Wickersham Dome Trail. Only about 45 miles outside of Fairbanks, this is a great spot for hiking, cross-country skiing, dog-mushing, fat-biking, or snowshoeing. Perfect endless landscapes of rolling hills.
Murphy Dome became a popular place to view the aurora a few years ago. However, I’m surprised at how few people leave the parking lot. One time I skied back from this location, there was a group of about 12 tourists lined up with tripods at the very beginning of the trail. They were taking photos through the willow trees. I think the parking lot would have been a better location. It’s only about a half-mile walk, snowshoe, or ski across open tundra. In winter, the snow is typically wind-packed and easy to walk. I always bring snowshoes or skis just in case.
A very brief walk on some obvious trails just left of the wind turbine on the north side of the parking area takes you out on to the tundra where you can wander to your heart’s content. Numerous stunted spruce stands dot the landscape with multiple rock outcroppings. An ATV trail is frequently traveled by snowmachines in the winter. They tend to pack the snow to where you can usually walk without snowshoes or skis. As long as it is clear, navigating back is easy as there are a radar dome and wind turbine with red flashing lights to lead you back to the parking area. The map below shows where the rock outcroppings are in relation to the parking area.
Be aware of moose in the area and especially on the road. I see moose almost every time I make the drive. There are occasionally bears on Murphy Dome spring-fall, but they don’t really frequent the area. Don’t wander beyond your comfort zone, it’s still possible to get lost even though it’s open tundra. The road is typically plowed in winter, but is often icy and almost always snow-covered October-April. Don’t pull off the road in winter, the snow on the side is often much deeper than it looks!
From Fairbanks head south on the Parks Highway (AK-3) and turn right on Sheep Creek Rd, just beyond Chena Pump Road. After 0.4 miles, turn left to stay on Sheep Creek Road. In 4.9 miles turn left on Murphy Dome Road. The first few miles are paved before turning to dirt (won’t matter in winter when snow-covered). Follow Murphy Dome Road for 15.5 miles until you come to a large parking area between the wind turbine and the radar dome. Be careful in the parking area, there can be some deep snow drifts in winter and deep mud in the summer.
This photo was taken early in the morning of October 6, 2015. I watched for a while as the moon came up over the horizon, followed by a string of the planets Venus, Mars, then Jupiter. I took this shot just as Jupiter rose above the trees and the sky was filling with twilight. It was absolutely incredible to see this all in the northern lights. More story and photos here!
Camping with fellow graduate students at the Granite Tors a few years ago. We managed to find a perfect little spot, about 8 miles in along the trail below the Flying Horseman Tor. If you ever have the chance to hike or backpack near Fairbanks, this is definitely one of the top trails. It’s about a 15-mile loop with 3,400 ft. of elevation gain. It can be done in a day if you’re in shape for it but also makes a very nice overnight trip.
This photo was taken from the Thorofare Ridge in Denali National Park near mile 60 along the Park Road. Looking over a gorgeous vista of the Thorofare River, red alpine tundra with a kettle pond nested up high, and the debris and vegetation covered Muldrow Glacier and, of course, Denali hovering high above all of it above the clouds.
A trumpeter swan feeding in the snowmelt at Creamer’s Field in Fairbanks, Alaska. The Trumpeter Swan is the largest native waterfowl in North America, the males averaging about 26 lbs and have wingspans that can reach 8 feet. The reach breeding age at 4-5 years and typically mate for life.
In the 1930s, trumpeters were brought to near extinction by overhunting, largely for their “decorative” feathers and for writing quills. Aggressive re-introduction work, primarily in the 1980s and 1990s by conservation groups in the US and Canada has led to a thriving population of over 22,000 breeding adults in Alaska and well over 45,000 in North America.
Every spring the snow is plowed and grain spread at Creamer’s Field to serve as a migratory stop-over for birds. This a joint effort by the DOT, Eielson Air Force Base, and the Department of Fish and Game as it helps keep the many migratory birds off of the airport runways. As we enter late spring and summer, they will disperse from the area and we’ll typically find them in ponds all over the interior of Alaska.
Cumberland Peak, or Peak A-117 between the head of the Loket Tributary, a large tributary to the Black Rapids Glacier and Eureka Glacier in the Eastern Alaska Range. This photo was taken from the Loket Tributary in April. The sky was such a deep blue, especially contrasted with the bright sunlight gleaming off the white snow.
Young Steller sea lions swimming in a larger raft near Glacier Island in Prince William Sound. Most of the adult male and female sea lions were basking on the rocky shore while the youngsters swam and played in the crystal clear water.
The northern lights appear on a windy evening while walking along the Angel Rocks to Chena Hot Springs Trail in the Chena River State Recreation Area. I’m always amazed by the stars out here. Like I forget every time how incredibly bright they are. It’s a gorgeous trail in the daytime too.
The end of summer brings wonderful color to the interior of Alaska. The leaves and undergrowth typically begin changing by the end of August and are well past peak by the time fall sets in at the end of September. Most of the deep color comes from the undergrowth, red leaves on berry bushes and dwarf birch cover the tundra floors. Then there’s the brilliant yellow and orange canopies of aspen and paper birch trees. This photo was taken at Peat Ponds on the north side of Fairbanks in the Goldstream Valley in early September.
This phenomenon is due to the interaction of light with ice crystals in the atmosphere, so it falls into the class of halos in atmospheric optics. Light pillars are typically strongest and highest with artificial light sources. However, slightly different conditions can cause pillars with the sun and moon as well.
Light pillars are caused by ice crystals reflecting relatively strong light sources to the viewer’s eye from plate-shaped ice crystals. So there isn’t actually a pillar of light shining over the light source like with light beams, but the viewer sees the light reflected off the flat surface of the ice crystals between the observer and the light source creating a virtual image, a kind of an illusion of a beam. A pillar will look different (or not exist) depending on the position of the observer due to the amount of and altitude of the ice crystals. This can be very apparent when seeing light pillars while driving as they may change in intensity over different altitudes rapidly while moving.
Light pillars are most commonly seen when it is very cold and very calm (no wind), so that the majority of plate-like ice crystals are oriented with the faces parallel to the ground. If it’s too windy, the plates are much too randomly facing to cause this effect.
Blue skies over the Trinity Basin in the Alaska Range. This region is the accumulation area for both the Black Rapids and Susitna Glaciers. The Mountains here are completely draped in ice and snow at about 8000 ft. in elevation. This area has been extensively studied for mass balance since 1972, primarily because Black Rapids is a surge-type glacier, last surging in 1936-1937 when the terminus of the glacier advanced rapidly at nearly 220 feet per day, approaching the Delta River. The Susitna Glacier, also originating in this icefield last surged in 1953.