The Excelsior Glacier flows south for about 6.5 miles (10.5 km) from the Sargent Icefield on the Kenai Peninsula to its terminus in Excelsior Lake, Alaska. The lake is drained by the Big Johnstone River that flows about 1.5 miles (2.4 km) and connects the lake to Johnstone Bay and the Gulf of Alaska.
Johnstone Bay is about 7 miles (11 km) across, on the southeast coast of the Kenai Peninsula between Cape Junken and Pinnacle Rock. It was named after James Johnstone, a British naval officer and explorer noted for having served as sailing master of the armed tender HMS Chatham and later acting lieutenant during George Vancouver’s 1791–1795 expedition to the Pacific Northwest.
The Excelsior Glacier has been retreating at a rate of about 330 feet (100 m) per year since 1984. In 1913, the glacier terminated on an outwash plain about 0.5 miles (1 km) from Johnstone Bay. In 1941, Excelsior Lake was in the initial stages of development about 5 miles (8 km) north of Johnstone Bay. By 1951, the terminus of the glacier had retreated as much as 2.6 miles (4.3 km), and Excelsior Lake had drained. Excelsior Lake grew to fill most of its potential tributary basin by the 1960s and is now an elongated and rapidly enlarging terminal lake. Read more here and here. Explore more of Johnstone Bay here: