Beloit Glacier flows northeast for about 2 miles (3.2 km) from an unnamed ice field on the Kenai Peninsula to Blackstone Bay in Prince William Sound, about 86 miles (138 km) southwest of Valdez and 9 miles (15 km) south of Whittier, Alaska. Beloit Glacier is a tidewater glacier with an ice front or terminus below sea level. The glacier rises about 2,000 feet (610 m) from sea level to the crest on an unnamed ice field. The ice field is north of the Sargent Icefield, separated by Kings Bay, and covers an area of about 123,520 acres (49,987 ha) on the northernmost of the Kenai Mountains. It consists of a series of connected accumulation areas that support several dozen outlet glaciers. It is bounded on the west by Trail Creek and Placer River and on the east by Kings Bay and Nellie Juan River. Blackstone Bay and Blackstone Glacier were named in 1899 for a miner who lost his life on the glacier in 1896. Other glaciers that descend into Blackstone Bay include Concordia, Northland, Beloit, Marquette, Lawrence, and Ripon Glaciers that were all named in 1910 by Lawrence Martin of the U.S. Geological Survey for colleges in Wisconsin. Other major named glaciers that drain from this ice field into either Cook Inlet or Prince William Sound include Portage, Burns, Whittier, Tebenkof, Rainey, Cotterell, Taylor, Claremont, Wolverine, Trail, Bartlett, Spencer, and Skookum Glaciers. Shakespeare Glacier was once connected to the icefield but is now detached. All of these glaciers have retreated significant distances since they were first observed.

Many late 19th and early 20th century geologists with the U.S. Geological Survey carried cameras as a standard part of their field equipment. Although most studies were not primarily focused on glaciers, many of the photographs now serve to provide a baseline of glacier position. For example, in 1909, Grant and Higgins visited and mapped all of the glaciers of the northern shore of Prince William Sound from Port Valdez westward to and including Blackstone Bay and most of the glaciers of the southern shore of the Kenai Peninsula. Of the more than 235 photographs they took, many were published in the 1913 summary of their observations. Like many of their contemporaries, Grant and Higgins realized the significance of systematic, sequential photography of glaciers. particularly when there is no time for detailed observation. Ralph S. Tarr of Cornell University and Lawrence Martin of the University of Wisconsin were involved in more than half a dozen expeditions to study the glaciers of southeastern and south-central Alaska including Prince William Sound. Several thousand photographs resulted from the expeditions, many of them were made by Oscar D. von Engeln, a professional photographer who became a geologist as a result of his involvement in these expeditions. In 1914, the results were published in Alaskan Glacier Studies and are still one of the most comprehensive treatments of Alaska’s glaciers.

In 1794, Captain George Vancouver made the first map of Prince William Sound and this was improved by Mikhail Tebenkov in 1849. These maps were inaccurate, probably because they were made by explorers who had not followed closely the topographic intricacies of the shoreline. On the maps of Vancouver and Tebenkof, a note about “ice and snow”, which undoubtedly refers to Blackstone Glacier based on proximity, was mapped in the wrong embayment and the error was not corrected until 1909 when Grant and Higgins made a hurried reconnaissance of the bay and determined the correct positions of the glacier fronts. They did not differentiate or name the many outlet glaciers, instead referred only to the “Blackstone Glacier that surrounds the head of Blackstone Bay and sending down from a very extensive ice field no less than ten ice streams”. They also noted evidence that the front of Blackstone Glacier had once reached the north end of Willard Island within the last two centuries of their visit based on the age and type of vegetation. Today, the island is an extension of the headland separating Beloit Glacier from Blackstone Glacier. In 1995, Blackstone Glacier had a length of 7.5 miles (12.1 km) and an area of 7,680 acres (3,108 ha), with a width at its face of 0.3 miles (0.5 km). Beloit Glacier had a length of 6.3 miles (10.1 km) and an area of 6,208 acres (2,512 ha), with a width at its terminus of 0.3 miles (0.4 km). In 2000, both glaciers still terminated at tidewater, but in 2004, they showed exposed bedrock along their margins and evidence of recent thinning. Read more here and here. Explore more of Beloit Glacier and Blackstone Bay here: