MacDonald Spit, Kasitsna Bay

MacDonald Spit, Kasitsna Bay

by | Jul 10, 2022

MacDonald Spit is a sediment deposition feature about 1 mile (1.6 km) long, caused by longshore drift from west to east, that forms the northwestern shore of Kasitsna Bay on the south coast of Kachemak Bay on the Kenai Peninsula, about 5 miles (8 km) northeast of Seldovia, Alaska. The local name was first published by the U.S. Geological Survey in 1951. The sediment forming the spit is sand, pebbles, and cobbles that are sourced mostly from eroding sea cliffs and Barabara Creek to the west. The sea cliffs are composed of rocks in the McHugh Complex, which is part of the Southern Margin composite terrane. The McHugh Complex is exposed at the base of MacDonald Spit and also at Nubble Point which forms the end of the spit, and this bedrock consists of basalt and chert. The basalt is mostly pillow and massive basalt, depositionally overlain by complexly folded and faulted radiolarian chert. The radiolaria range in age from Middle Triassic to Early Cretaceous. Between these bedrock outcrops, unconsolidated sediments accumulated during the Holocene creating a tombolo which is an island that becomes attached to the mainland by a narrow strip of land such as a spit or bar. Once attached, the island, in this case Nubble Point, is known as a tied island. Sediments are continuing to accumulate through the process of longshore drift forced by the prevailing or primary wind and wave direction which is from the west. Waves that arrive and break on a beach at an oblique angle cause sediment to be moved along the beach in a zigzag pattern. Finer sediments are transported higher and farther along the beach than coarser particles. Longshore drift is augmented by the strong tidal currents in Kachemak Bay which also transport sediment. MacDonald Spit exhibits a hook extending from Nubble Point to the south into Kasitsna Bay. This is a recurved spit caused partly by wave refraction that wraps around the end of the spit and also by secondary winds that blow from the northeast. The recurved end of the spit creates a protected environment where a sandflat or mudflat has formed in Kasitsna Bay.

MacDonald Spit was probably first used as a summer camp by the earliest humans to reside in Kachemak Bay because it allows ready access to marine resources for exploitation. In the summer of 1930, Frederica de Laguna conducted an archaeological survey of Cook Inlet including Kachemak Bay. A village site on Yukon Island about 3 miles (5 km) northeast of MacDonald Spit was investigated and a chronology of human use spanning 1500 years was assembled based on midden artifacts. Jack Fields, a resident of Seldovia assisted de Laguna that summer and found a concave stone lamp on the beach of MacDonald Spit near the site of a midden. Also found were traces of a large rectangular prehistorical house pit, or barabara used by the Alutiiq people. Another midden was excavated at the base of the spit and revealed human bones, stone splitting adzes, a slate knife, and an ivory statuette, all from the period pre-dating Russian occupation. When European explorers arrived, the southern coast of Kachemak Bay was occupied by Sugpiat Alutiiq and the northern shore by Dena’ina Athabascan. The mix of cultures inevitably led to conflicts over resource use and at least one island at the mouth of Tutka Bay was used as a refuge island called Q’na’qesle, or present-day Grass Island. In the 18th century, Russian fur hunters called promyshlenniki were among the first European visitors to Kachemak Bay. In 1778, Captain James Cook sailed into Cook Inlet in search of the fabled Strait of Anián or Northwest Passage across the North American continent. In 1786, Stepan Zaikov of the Lebedev-Lastochkin Company established a trading post at the mouth of the Kenai River. These fur traders subjugated the Aleut and Alutiiq people and forced the males to hunt sea otters to supply the maritime fur trade. After the Alaska Purchase in 1867, when the territory was transferred from Russia to the United States, Kachemak Bay became a popular destination for miners, fishers, and fur trappers. The miners were mostly en route to the goldfields of upper Cook Inlet and the interior, but the fishers were interested in exploiting the bay for herring and salmon. Fox farms were established on several islands at the mouth of Tutka Bay and on MacDonald Spit that operated through the early 1900s.

In the 1950s, Kasitsna Bay was homesteaded by Harley O. Ekren and his family who deployed a fish trap to catch salmon. In 1955, they started a cannery called the Ekren Packing Company to process clams, salmon, and Dungeness crabs. When fish traps were banned following Alaska statehood in 1959, the Ekren’s used gill nets and purse seines until the cannery closed in 1975. Today, MacDonald Spit is subdivided into 36 remote residential lots mostly providing homes for a seasonal community, and some residents still use set nets to catch salmon. Set gillnets are a single wall of netting kept vertical by a floating line or headrope and a weighted ground line or footrope. Small floats, usually shaped like ovals or cylinders and made of solid plastic are evenly distributed along the floating line, while lead weights are either evenly distributed along the ground line lead cored rope can be used with no additional weight. The net is set on the bottom, or at a distance above it and held in place with anchors or weights on both ends. Set gillnets are handled from small boats or from shore and are popular with subsistence and personal use fisheries because of the low cost and no specialized gear is needed. Commercial salmon fishing in Lower Cook Inlet utilizes purse seine nets and set gillnets. The financial success of the commercial fleet relies on strong returns of pink salmon. These pink salmon runs, and many of Lower Cook Inlet’s sockeye runs, are heavily enhanced by hatchery production. Commercial fishing boats participate in cost recovery and pay a 2% salmon enhancement tax to the Cook Inlet Aquaculture Association. Personal use salmon fisheries of Lower Cook Inlet include the Kachemak Bay setnet fishery, which requires a permit and targets coho salmon, and the China Poot dip net fishery, which does not require a permit and targets enhanced sockeye salmon. Read more here and here. Explore more of MacDonald Spit and Kachemak Bay here:

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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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