Alaska Triangle -- Mendenhall Glacier and the Mechanics of Disappearance
Alaska Triangle -- Mendenhall Glacier and the Mechanics of Disappearance
The Mendenhall Glacier
The Mendenhall Glacier is among the most accessible and most studied glaciers in Alaska, located just 12 miles from Juneau -- the southeastern vertex of the Alaska Triangle. As a visible, accessible, scientifically monitored glacier situated at the geographic corner of the Triangle, it provides an ideal case study for understanding the glacier physics that accounts for so many of the Triangle's permanent disappearances.
| Feature | Detail |
|---|---|
| Location | Tongass National Forest; 12 miles northwest of Juneau, Alaska |
| Type | Valley glacier; tongue of the Juneau Icefield |
| Length | Approximately 12 miles from icefield to terminus |
| Area | Approximately 36 square miles (glacier face); the Juneau Icefield that feeds it covers approximately 1,500 square miles |
| Movement | The glacier advances at varying rates; historically moved at approximately 1.5-2 feet per day at the terminus |
| Status | The glacier has retreated significantly since the mid-20th century due to warming temperatures; the terminus has retreated more than 1.75 miles since 1958 |
| Scientific monitoring | Continuously monitored by the U.S. Forest Service and University of Alaska; glaciological research ongoing |
Glacier Physics: How Wreckage Disappears
The Mendenhall Glacier demonstrates in miniature the processes that have made wreckage recovery impossible in hundreds of Alaskan glacier-adjacent crashes:
Surface entry: When an aircraft impacts a glacier, the initial collision breaks the surface snow and ice layer, driving wreckage downward into the glacier's interior. In summer months, surface meltwater assists in drawing material deeper. In winter, snowfall rapidly covers any surface evidence.
Ice transport: Glacial ice moves as a viscous solid -- like an enormously slow river. Material incorporated into the glacier's interior is transported toward the terminus at the rate of the glacier's flow, embedded in ice. It does not stay at the crash location.
Compression and grinding: As the glacier moves over irregular bedrock, material within it is compressed and ground. Aircraft wreckage entering a glacier is physically destroyed by this process over years to decades.
Terminal emergence: Eventually, material that entered the glacier far upslope emerges at the glacier's terminus -- sometimes decades after the original event, having traveled miles from where it entered the ice. Biological remains may be preserved in glacial ice for extraordinary periods; mechanical wreckage is typically destroyed.
Known Cases of Glacial Wreckage Recovery
Several Alaskan aviation cases illustrate the glacier concealment-and-emergence phenomenon:
- Aircraft lost in the 1940s and 1950s on Alaskan glaciers have had portions of their wreckage emerge at glacier termini in the 1990s and 2000s -- 50+ years after the original accident
- In some cases, remains of aircrew have emerged from glacier ice, partially preserved, far from the original crash site and decades after the crash
- Ground expeditions to recover wreckage from glacier-surface crashes have found it already covered within hours by snowfall
What This Means for Unsolved Cases
For aircraft lost on or near Alaskan glaciers -- including several of the Triangle's signature cases -- the glacier physics means that the absence of wreckage is not mysterious; it is expected. The more interesting question is whether wreckage will eventually emerge at a glacier terminus, and if so, when and where. The answer to this depends on where in the glacier system the aircraft entered, the glacier's speed, and the distance to the terminus.
