Turner Glacier starts at an elevation of roughly 11,000 feet (3,353 m) on the eastern flank of Mount Cook in the Saint Elias Mountains and flows generally southeast for 21 miles (34 km) to Disenchantment Bay at the head of Yakutat Bay, about 214 miles (344 km) east-southeast of Cordova and 33 miles (53 km) north of Yakutat, Alaska. The Tlingit language name for the glacier is Sít’ Kusá, meaning ‘narrow’ glacier. In 1891, Israel Cook Russell, who explored much of Malaspina Glacier, Yakutat Bay, and the Mount Saint Elias region named it ‘Dalton Glacier’, to honor John Dalton, a local miner and pioneer. However, Dalton was subsequently accused of murder and Russell made a request to the Board on Geographic Names to change the name to honor John H. Turner, who spent three years in Alaska making surveys for the U.S. Geological Survey. Disenchantment Bay is a translation from the Spanish ‘Puerto del Desengaño’, the name bestowed by Captain Alessandro Malaspina in 1792, referring to his frustration in not finding a northwest passage from Yakutat Bay to the Atlantic.

This part of Alaska consists of a geologic collage of seven tectonostratigraphic terranes that formed far to the south in the equatorial Pacific Ocean and rafted northward on oceanic tectonic plates, eventually accreting to Alaska and the North American continent. The first to arrive was the Windy terrane that accreted to the continent in the Triassic and early Jurassic time. This was followed by the Wrangellia terrane, that had merged with the Alexander terrane in the Pacific and both accreted to the continent during the Cretaceous. Overlying parts of the Wrangellia terrane, is the Peninsular terrane that consists chiefly of a Jurassic volcanic arc. The Border Ranges Fault separates Wrangellia terrane from the Southern Margin Composite terrane which consists of the Chugach terrane that formed in a deep oceanic trough during the Cretaceous, and the Prince William terrane that formed as a deep-sea fan and volcanic rock during the Paleogene. The last to arrive and is currently still accreting to the continent is the Yakutat terrane that consists of a series of Jurassic and Cretaceous sedimentary rocks with minor amounts of oceanic volcanics. The rocks exposed around the Turner Glacier represent the Yakutat terrane and are mostly highly deformed greywacke, siltstone, and argillite.

The Turner Glacier surged five times between 1983 and 2013. Glacier surges are defined as periodic instabilities that result in rapid surface velocities and ice mass redistribution, resulting in a temporary terminus advance. Less than one percent of all glaciers worldwide are classified as surging, and Alaska and western Canada have the highest concentration, with 113 surge-type glaciers. Surge events have the potential to strongly influence glacier mass balance, as they transport a large mass of ice from the high elevation accumulation zone, across the dynamic balance line, to the lower elevation receiving zone where ablation rates are higher and mass loss is accelerated. There are presently two main hypotheses to explain what triggers glacier surges. One hypothesis is called the polythermal switch. This occurs when that glacier ice, which is normally frozen to the rock bed, rapidly transitions to warm ice detached from the bed, triggering flow acceleration. The second hypothesis is called the hydrologic switch, where the surge is caused by the transition from an intra-ice drainage system with low basal water pressure, to a drainage system with high basal water pressure that triggers sliding. Read more here and here. Explore more of Turner Glacier and Disenchantment Bay here: