The Black Rapids Glacier is what is known as a surge-type glacier in a region of the Eastern Alaska Range known as the Hayes Range. At nearly 40 km (25 miles) in length, it is one of the largest glaciers in the Alaska Range east of Denali. It is located just west of the Richardson Highway between Delta Junction and Paxson on the opposite side of the Delta River (the river to which it drains). There is an overlook at Mile 225.4 where it’s possible to get a small glimpse of ice near the glacier’s terminus on a clear day. It’s also visible from the nearby Black Rapids Lodge and historic roadhouse. You can see many mounds or piles of rock in the valley that are old terminal moraines, remnants of previous surges of the glacier.
Surge-type glaciers undergo periodic, rapid advances and retreats, followed by long periods of stagnation or quiescence. During a surge, a glacier can flow up to 100 times its normal speed. The Black Rapids Glacier last surged in 1936-1937, advancing nearly 6.5 km (4 miles) and earning it the nickname the “galloping glacier”. This advance threatened to reach or cross the Delta River, which had the potential to flood the valley.
Today, both the Richardson Highway and the Trans-Alaska Pipeline wind their way through this corridor in the Delta River Valley. Because of the potential implications of damage due to a surging glacier, and the ease of access to a surge-type glacier, the Black Rapids Glacier is one of the most studied glaciers in the world.
2002 Earthquake and Landslides
The Black Rapids Glacier lies along the Denali Fault, a 600-mile long strike-slip fault. On November 3, 2002, a 7.9 magnitude earthquake with an epicenter on the nearby Susitna Glacier triggered three massive rockfalls across the Black Rapids Glacier (as well as many other landslides in the Alaska Range). These landslides cover approximately 11 km2 (4 square miles) of the glacier surface in the ablation zone. They were so powerful that the rock debris ran across the entire 2.4 km (1.5 miles) width of the glacier and began to climb up the other side of the valley!
The above photo shows a thin section of exposed glacier between two of the landslides. The thickness of the landslide debris itself is deceptive, on average it’s only about 1-3 meters thick. The reason it looks so thick here is that the rocky cover insulates the ice beneath it from melting in the summer months. The surrounding ice melts much faster, so over the years, the difference in the ice thickness keeps increasing, causing the steep ice cliff. The above photo was taken almost 11 years after the landslides.
High up on the glacier are remnants of the last glacial surge. The aptly named “potholes” are cauldron-like depressions in the ice that often fill with water in the summer. When the glacier surged, it left the accumulation area partially depleted of ice, since the glacier is essentially “stretching” out. The ice was largely crevassed, but over time those crevasses slowly heal. The potholes are what is left of those crevasses.
In summer, these potholes often fill with water. Many are connected, either supraglacially, or englacially and have been observed draining on numerous occasions. The interconnectedness of these potholes has led to some interesting hydrology including observations of one draining subglacially while a downstream pothole fills. There have been stories from mountaineers in winter witnessing water shooting up out of the glacier like a geyser.
The Black Rapids Glacier has numerous ice-dammed lakes on the margins of the glacier. These occur where the glacier meets the sides of the mountains, although some are simply locked in moraines. Most of these are located on the northern margin. Many of these lakes have been observed to fill and drain throughout late spring and summer. The resulting increase in subglacial hydraulic pressure causes increases in the ice-flow velocity for hours to days.
Notable Nearby Peaks
The majority of big peaks in the area lie at the head of small tributary glaciers on the north side of the Black Rapids Glacier (see map above).
Peak Elevation: 2740 m (11,400 ft)
The south face of McGinnis Peak is visible from Black Rapids about 18 km (11 miles) from the glacier terminus. It has a striking couloir down the center of this face that is unclimbed. Most of the established climbing routes on McGinnis are accessed from the northern side.
Peak Elevation: 3860 m (12,660 ft)
Mt. Shand is the tallest peak directly adjacent to the Black Rapids Glacier. It’s located approximately 26 km (16 miles from the terminus of the glacier. The highest peaks in the Hayes Range are just beyond the pass where the connected Susitna Glacier descends to the west.
2479 m (8133 ft)
While it’s far from the tallest mountain in the area, Meteor Peak is still very prominent above the Black Rapids Glacier. It’s also one of the few peaks that are commonly accessed by climbers from Black Rapids. Meteor Peak is on the south side of the glacier about 25 km (16 miles) from the terminus.
Basically, no. The local air taxi service, Golden Eagle Outfitters offers flightseeing tours over the glacier. That’s probably the best way to experience this region.
Adventurers and hikers wishing to hike in the area may be quickly dismayed by the difficulty of accessing the glacier. This is especially true in the summer months. The Delta River must be crossed to access the valley, and at the location of Black Rapids, the river is rife with large, unforgiving rapids. More reasonable summer access is further south, where the river is a bit calmer and can be more easily negotiated with a pack raft. This would make for about a 6-8 mile approach to the messy, debris-covered terminus of the glacier. A lot of experience on glaciers is needed to navigate terminus lakes and then cross the moraines and lastly the landslide debris safely.
Access is easier in the winter when (if) the river is frozen. It’s a long hike or ski to access, but mountaineers frequently use the multi-day route up the glacier to access some of the peaks in the Hayes Range. Glacier travel knowledge, crevasse rescue, and avalanche preparedness are all necessary for winter.
I will publish more route information in the future, but lacking proper GPS tracks and details, I’m choosing not to post now. I hope to make both summer and winter trips in 2021 to record route info. Without that, any guide I write could be misleading and dangerous. Plus, the skills you need to safely navigate any route to this area would make a written guide to it mostly unnecessary.
References and Further Reading
Kienholz C, Hock R, Truffer M, Bieniek P and Lader R (2017) Mass Balance Evolution of Black Rapids Glacier, Alaska, 1980–2100, and Its Implications for Surge Recurrence. Front. Earth Sci. 5:56. doi: 10.3389/feart.2017.00056
Rupture in South-Central Alaska—The Denali Fault Earthquake of 2002, Gary S. Fuis and Lisa A. Wald, February 5, 2003. USGS Fact Sheet 014-03
Shugar, D. H., Rabus, B. T., Clague, J. J., and Capps, D. M. (2012), The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches, J. Geophys. Res., 117, F01006, doi:10.1029/2011JF002011.
Sturm, M., & Cosgrove, D. (1990). An unusual jökulhlaup involving potholes on Black Rapids Glacier, Alaska Range, Alaska, U.S.A. Journal of Glaciology, 36(122), 125-126. doi:10.3189/S0022143000005670