Cataract Glacier flows to the southern shore of Surprise Inlet, a fjord in Prince William Sound, about 51 miles (82 km) east-southeast of Anchorage and 20 miles (32 km) northeast of Whittier, Alaska. The glacier originates from the north flank of Peak 5541 in the Chugach Mountains and flows northeast for 2.1 miles (3.4 km) and terminating at the head of a stream, which continues for 0.5 miles (0.8 km) to the fjord. The name “Cataract Glacier” was given in 1899 by members of the Harriman Alaska Expedition. Surprise Inlet extends west for 2.5 miles (4 km) from Harriman Fjord to the tidewater terminus of Surprise Glacier. The retreat of the glacier has exposed bedrock consisting of partially metamorphosed sedimentary rocks from the Valdez Group. These rocks formed approximately 145 million years ago, during the Late Jurassic or Early Cretaceous period, as turbidites in a deep ocean trench. The Valdez Group is part of the Southern Margin composite terrane, one of the world’s largest subduction-related accretionary complexes. This terrane is now visible in Prince William Sound and the Kenai Peninsula.

In 1899, the Harriman Expedition to Alaska included Henry Gannett, a notable American geographer. In 1879, he lobbied the U.S. Congress to centralize U.S. mapping functions into a single government agency, which became the U.S. Geological and Geographical Survey—later officially named the U.S. Geological Survey. Gannett is considered the “Father of the Quadrangle,” now the standard 7.5-minute map used by the U.S. Geological Survey, forming the basis for topographical maps in the United States. In 1888, Gannett was a founding member of the National Geographic Society and served on its board until 1909. In 1890, he and Thomas C. Mendenhall of the U.S. National Geodetic Survey campaigned to establish the U.S. Board of Geographic Names to create official names for locations in the United States. In 1893, he wrote A Manual of Topographic Methods, which standardized surveying and mapping processes. Three years later, during his final year with the U.S. Geological Survey, he introduced the use of standard bronze surveyors benchmarks, which have since become ubiquitous. In 1899, he was invited, along with other elite scientists, to join the Harriman Alaska Expedition.

Gannett’s map of Harriman Fjord, drawn in 1899, shows the front of Surprise Glacier near where the Cataract Glacier reached tidewater. In 1909, Ulysses S. Grant and Daniel F. Higgins photographed the glaciers of Surprise Inlet and determined that Surprise Glacier had retreated about 1.1 miles (1.8 km) from its 1899 position. However, the Cataract Glacier terminus showed no noticeable change in position since 1899. In 1910, Cataract Glacier was advancing and overriding shrubs and willows along its margin when Lawrence Martin visited. In 1914, Dora Keen noted that the glacier’s terminus had not changed since Martin’s visit. By 1925, Keen observed a small recession since 1914, but the glacier’s terminus was still at tidewater. In 1931, William O. Field noted that the terminus of the glacier had retreated from tidewater but was thickening at higher elevations. By 1935, the glacier had readvanced to tidewater but was narrowing along its margins. In 1938, during another retreat, Bradford Washburn photographed the glacier. This retreat exceeded 1,600 feet (500 m) and continued through Field’s last observation in 1968. From 1974 to 2004, Bruce Molnia made several observations, noting that the terminus retreated about 1,000 feet (300 m) with significant thinning and narrowing of the ice. Today, Cataract Glacier is no longer tidal, and the terminus is about 0.5 miles (0.8 km) from the inlet. Read more here and here. Explore more of Cataract Glacier and Surprise Inlet here: