Fortification Bluff is a sea cliff more than 3 miles (4.8 km) long that rises almost vertically to 1,200 feet (366 m) on the south face of Step Mountain in Kamishak Bay, on the Cook Inlet shore of the Alaska Peninsula, about 125 miles (201 km) northwest of Kodiak and 82 miles (132 km) west-southwest of Homer, Alaska. The bluffs were named in 1914 by the US Coast and Geodetic Survey for the fortress-like appearance of the rock cliffs. The name ‘Kamishak’ is a transliteration from Alutiiq adopted by early Russian fur traders and was first published in 1826 as ‘Kamyshatskaya Bay’ by Gavril Sarychev. The rock at Fortification Bluff is mostly sandstone and siltstone of the Jurassic Naknek Formation. Alaska is a collage of terranes—pieces of the earth’s crust transported on different tectonic plates and accreted to the North American Plate. For example, the Alaska Peninsula is underlain by the Peninsular terrane, thought to have originated far south in the Pacific Ocean. The Bruin Bay Fault uplifted the rocks of this terrane, which were subsequently eroded, deposited into an adjacent ocean basin, and eventually lithified to form the Naknek Formation, which is mostly sandstone, conglomerate, and the Snug Harbor Siltstone that consists mainly of dark-gray to black siltstone. Since the Last Glacial Maximum, the cliffs have retreated under the erosive forces of Cook Inlet’s waves. Intense storms in lower Cook Inlet generate large waves that strike the cliffs with enough force to cause significant erosion. Wave-cut platforms have developed where destructive waves hit the cliff face, creating an undercut or notch between the high and low water marks—mainly through abrasion, corrosion, and hydraulic action. The overhanging weight eventually triggers a collapse, causing the cliff to retreat landward. The cliff’s base forms a nearly level intertidal and subtidal platform. The extreme tidal range in Cook Inlet results in very wide platforms that provide an extensive habitat for marine plants, invertebrates, and their predators.

During the late prehistoric and historic periods, the Dena’ina, Alutiiq, and Yup’ik used Kamishak Bay to access several traditional portage routes linking Iliamna Lake and Cook Inlet. The bay was also an important hunting region for the Dena’ina. In 1794, Captain George Vancouver explored the area. Although navigation charts from that time show ‘Bourdieus Bay’, he never mentioned the name in his journals; so it may have originated with Captain George Dixon. Both Dixon and Vancouver served on Captain James Cook’s third voyage in 1778 aboard HMS Resolution. Dixon recognized the commercial potential along the northwest coast of America and later became a partner in King George’s Sound Company to develop the fur trade in British Columbia and Alaska. In September 1785, Dixon and trader Nathaniel Portlock left England with two ships on a three-year voyage. During the summers of 1786 and 1787, Dixon explored the shores of present-day British Columbia and the Gulf of Alaska coast, including the Dixon Entrance of Cook Inlet and Kamishak Bay. In 1818, after Alexander A. Baranov of the Russian-American Company retired, the Russian post at Aleksandrovsk (present-day Nanwalek) was downgraded to a one-man station, and most of the structure was moved to the Nushagak River on Bristol Bay. In 1867, the Alaska Purchase transferred the territory from Russia to the United States, and the Alaska Commercial Company assumed control of the Russian trading posts. During the 1880s and 1890s, Yup’ik hunters from Bristol Bay migrated each spring to Kamishak Bay to hunt sea otters for Alaska Commercial Company agent John W. Clark at Nushagak. Numerous otter-hunting camps were scattered along the shores of Kamishak Bay from Augustine Island south to Cape Douglas. Hunters transported seal and otter pelts to the Alaska Commercial Company warehouse in Kachemak Bay at Seldovia.

The sea otter is the smallest marine mammal and the largest member of the weasel family. Sea otters forage in shallow coastal waters, diving to the bottom to catch prey and surfacing to eat. Their main prey includes sea urchins, crabs, clams, mussels, octopus, fish and other marine invertebrates. Sea otters are keystone predators that structure nearshore marine ecosystems based on prey selection. The history of sea otters in Kamishak Bay is unclear. They were hunted nearly to extinction in the late 1700s and 1800s for the maritime fur trade. Surveys suggest that a small remnant population remained in the early 1900s. Because this population centered on Augustine Island, most surveys covered only its shoreline and possibly Shaw Island and Cape Douglas. The population probably grew throughout the 1940s and 1950s, and by 1965 some range expansion to the south had occurred. Counts made between 1969 and 1971 indicated an increase in numbers around Augustine Island and in the waters immediately to its north and west. There was also substantial movement from Cape Douglas to the south near Shakun Rocks. Most likely, densities in Kamishak Bay increased steadily through the 1960s before stabilizing or declining slightly as animals emigrated to the southwest and possibly to the east across Cook Inlet to Kachemak Bay. By the 1990s the population range extended from northern Kamishak Bay to Cape Nukshak in Shelikof Strait. Sea otters inhabiting the Alaska Peninsula coast between Cape Douglas and Cape Chiniak are probably part of the original Kamishak Bay population, while those further south likely belong to the large group centered near Kujulik and Amber Bays in Aniakchak National Monument and Preserve. Today the southwest Alaska stock of sea otters extends more than 1,553 miles (2,500 km) from Cook Inlet to Attu Island in the western Aleutian Archipelago. However, this population declined substantially—perhaps as much as 90 percent—between about 1990 and 2015. Read more here and here. Explore more of Fortification Bluff and Kamishak Bay here: