The Kashteen Peninsula is located in Wrangell-Saint Elias National Park and Preserve on the eastern shore of Icy Bay, between Tsaa Fjord to the south and Guyot Fjord to the north, about 149 miles (240 km) east-southeast of Cordova and 73 miles (118 km) northwest of Yakutat, Alaska. It is emerging from beneath the retreating Guyot Glacier. Kashteen and Tsaa are names from the Tlingit language; the latter refers to the earless, or true seal. Guyot Glacier was named after Arnold H. Guyot, a geologist and geographer at Princeton University. The south coast of Alaska consists of a collage of seven tectonostratigraphic terranes that formed in the equatorial Pacific Ocean and rafted northward on oceanic plates, eventually accreting to the North American continent. The Yakutat terrane is in the process of accreting and is bounded on the east by the Fairweather Fault and on the north by a system of faults in the Chugach and Saint Elias Mountains. The Kashteen Peninsula and most of the bedrock exposed by the retreating Guyot Glacier represent the Yakutaga Formation, which consists of mudstone, siltstone, sandstone and diamictite deposited during the Miocene and Pliocene (about 23 million to 2.5 million years ago) in a marine and glacio-marine clastic continental-shelf environment.

In 1794 Lieutenant Joseph Whidbey, of the Vancouver Expedition, explored the coast near present-day Icy Bay. At the time, Guyot Glacier was joined with the Tyndall and Yahtse glaciers to form a massive ice front reaching the Gulf of Alaska, thought to be the western lobe of the Malaspina Glacier. Glacial retreat began in 1899, gradually exposing what is now Icy Bay. Guyot Glacier had an ice front over 6 miles (10 km) wide and was calving into deep water, which drove a rapid retreat of more than 31 miles (50 km). The peninsula was completely covered by the glacier when photographed in 1938; by 1969 its tip was exposed and Guyot Glacier had separated into three ice streams. By 1986 the glacier had retreated a considerable distance up a newly exposed Guyot Fjord. In 1995 a small ice mass of 74 acres (30 ha) still covered part of the peninsula; by 2000 the stranded ice masses were gone, and by 2010 the area supported considerable vegetation.

Tidewater glaciers terminate in the ocean at either a grounded terminus or a floating ice tongue. Alaska’s tidewater glaciers lie on the seaward side of the Kenai, Chugach, Saint Elias and Coast mountains; roughly 50 are active, though the exact number varies with the advance and retreat of individual ice streams. Almost all tidewater ice fronts have now withdrawn into inner fjord areas. As recently as 1960, the tidewater glaciers of Icy Bay shared a single terminus but have since separated into independent fronts. There are now five tidewater glaciers in the bay, the largest being Yahtse Glacier. A sixth, the Moraine or Apron Glacier, has recently retreated from tidewater. Many tidewater glaciers follow a repeating temporal cycle: a slow advance over centuries until thinning near the terminus triggers a rapid retreat completing within decades, stabilizing only when the glacier has withdrawn into shallow water. While climate change can initiate the retreat phase, once underway the glacier’s behavior is only weakly influenced by climate, and glacier geometry becomes the primary driver. Read more here and here. Explore more of Kashteen Peninsula and Tsaa Fjord here: