Nabesna Glacier

The Nabesna Glacier is a massive river of ice located in Alaska. It is a significant geographic feature within the Wrangell Mountains. This glacier is classified as a valley glacier. A valley glacier is a large mass of ice that moves through a mountain valley. The Nabesna is a record-breaking glacier. It is the longest valley glacier in North America. It also holds the title of the longest interior valley glacier in the world.

The glacier forms through a complex process of accumulation and flow. It is fed by deep snowfall in the Wrangell Mountains. This snow comes from an extensive icefield. This icefield covers the northern flanks of Mount Wrangell. Mount Wrangell is a large shield volcano. The glacier also receives ice from approximately 40 tributary glaciers. Tributary glaciers are smaller glaciers that flow into a larger main glacier. These many sources help maintain the vast expanse of the Nabesna.

Gravity pulls the ice along a specific path through the mountains. Initially, the glacier flows in an easterly direction. It moves past several prominent volcanic peaks. These include Mount Blackburn and the Atna Peaks. After this initial path, the glacier changes direction. It turns toward the north. The glacier eventually reaches its terminus, which is its end point. This terminus sits at an elevation of about 3,000 feet.

History helps us understand how the glacier was named and discovered. F. C. Schrader named the glacier in 1902. He was a member of the U.S. Geological Survey. He chose the name based on the Nabesna River. The glacier serves as a vital route for many people today. It provides the normal access into the heart of the eastern Wrangell Mountains. Ski mountaineers and climbers use the ice to travel. Scientists also visit the glacier to conduct research.

The glacier is a unique place for transportation and travel. Small bush planes can actually land on the central portion of the ice. This usually happens at elevations between 6,000 and 7,000 feet. Pilots must wait for specific conditions to land safely. The winter snow must cover the crevasses. Crevasses are deep cracks that form in the moving ice. When the snow covers these cracks, the surface becomes more stable for landing.

Scientists have observed that the Nabesna Glacier is changing over time. The glacier has been undergoing a slow, near-continuous retreat. A retreat means the glacier is shrinking. This process has been happening since at least the early 1900s. There is evidence that the retreat may have started even earlier. Glacial deposits found much further down the valley suggest a massive past size. The glacier may have once been over 200 miles long.

Finally, the glacier plays a major role in the local water system. As the ice melts at its terminus, it creates the Nabesna River. This river flows in a northward direction. It travels through the Tetlin National Wildlife Refuge. Eventually, the Nabesna River flows into the Tanana River. This connection shows how the glacier supports the broader environment of Alaska. The movement of ice and water links the mountains to the river systems below.