Cataract Glacier, Surprise Inlet

Cataract Glacier, Surprise Inlet

by | Oct 8, 2022

Cataract Glacier starts from the north flank of Peak 5541 in the Chugach Mountains and flows northeast for 2.1 miles (3.4 km) through a steep valley to its terminus at the head of a stream that flows for another 0.5 miles (0.8 km) to the southern shore of Surprise Inlet in Prince William Sound, about 51 miles (82 km) east-southeast of Anchorage and 20 miles (32 km) northeast of Whittier, Alaska. The descriptive name was given in 1899 by members of the Harriman Alaska Expedition. Surprise Inlet is a fjord that now extends west for 2.5 miles (4 km) from Harriman Fjord to the tidewater terminus of Surprise Glacier. The underlying bedrock exposed by the retreating glacier is partially metamorphosed sedimentary rocks of the Valdez Group that formed during the Late Jurassic or Early Cretaceous, or about 145 million years ago, 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 now exposed in Prince William Sound and the Kenai Peninsula.

The Harriman Expedition to Alaska in 1899 included Henry Gannett, an influential American geographer. In 1879, he lobbied the U.S. Congress to centralize the mapping functions of the United States into one government agency called the U.S. Geological and Geographical Survey, although the name U.S. Geological Survey would officially be approved. He is considered the ‘Father of the Quadrangle’, now the standard U.S Geological Survey 7.5-minute map, and the basis for topographical maps in the United States. In 1888, Gannett was one of the founding members of the National Geographic Society, and he served on the 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 was the basis for standardizing surveying and mapping processes, and three years later in his last year with the U.S. Geological Survey, he started the use of standard and now ubiquitous bronze surveyors benchmarks. In 1899, he was invited 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 practically at the point 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 the 1899 position. But the Cataract Glacier terminus did not show any noticeable change in position from 1899. In 1910, Cataract Glacier was advancing and overriding shrubs and willows along the margin when Lawrence Martin visited the glacier. In 1914, Dora Keen visited the glacier and observed that the terminus of the glacier had not changed position since Martin’s visit. In 1925, Keen observed that the glacier had experienced a small recession since 1914 but that its terminus was still at tidewater. In 1931, William O. Field noted that the terminus had retreated from tidewater but that it was thickening at higher elevations. By 1935, the glacier had readvanced to tidewater but was showing signs of narrowing along its margins. In 1938, another retreat was underway when Bradford Washburn photographed the glacier. This retreat was greater than 1,600 feet (500 m) and continued through Field’s last reported observation of the glacier in 1968. From 1974 to 2004, Bruce Molnia made several observations of the glacier and the terminus retreated about 1,000 feet (300 m) with considerable thinning and narrowing of the ice. Today, Cataract Glacier is no longer tidal and the terminus is situated about 0.5 miles (0.8 km) from the inlet. Read more here and here. Explore more of Cataract Glacier and Surprise Inlet here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2021 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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