Grewingk Glacier originates from an icefield in the Kenai Mountains and flows northwest to the southern shore of Kachemak Bay, about 25 miles (40 km) northeast of Seldovia and 16 miles (26 km) east-southeast of Homer, Alaska. The glacier extends 11 miles (18 km) from the icefield to a proglacial lake approximately 2 miles (3.2 km) long. This lake is drained by Grewingk Creek that flows 3.5 miles (5.6 km) to Kachemak Bay. It was named in 1880 by William H. Dall of the U.S. Coast and Geodetic Survey in honor of Constantin Grewingk, who published a study on Alaska’s geology and volcanism in 1850. The eastern and southern sides of the Cook Inlet basin are bordered by a Paleogene and Cretaceous or older subduction-related accretionary wedge known as the Southern Margin composite terrane. This terrane comprises sedimentary rocks formed in a deep ocean trench and includes the Chugach and Prince William terranes as well as the Ghost Rocks Formation. The Chugach terrane consists of the Seldovia Complex, McHugh Complex, and the Valdez Group. The McHugh Complex forms the bedrock beneath and around Grewingk Glacier, consisting of partially metamorphosed sandstone, siltstone, greywacke, arkose, and conglomerate. An igneous intrusion from the Mesozoic era, composed of gabbro, is exposed at the glacier’s base. Below Grewingk Lake, unconsolidated sediments from the Late Pleistocene and Holocene, including outwash and alluvial deposits, largely cover the bedrock. The southwest part of the Kenai Peninsula experienced glaciation three or more times during the Quaternary period. During the earliest glaciation, ice flowed westward from the Kenai Mountains, overrunning the Kenai Lowlands and merging with a broad ice stream moving south through the Cook Inlet trough. In each of the subsequent, less extensive glaciations, ice flowed from the Kenai Mountains into the Kachemak Bay trough.

The earliest settlers of the Cook Inlet basin remain unknown. However, archaeological sites indicate human presence between 10,000 and 7,500 years ago, following the retreat of the glaciers. These early inhabitants were highly mobile hunter-gatherers who traveled in small groups and relied heavily on large land mammals for food. Around 4,200 years ago, new settlers arrived, specializing in marine mammal hunting. Over time, these distinct groups traded, intermarried, and sometimes clashed. From 3,000 to 1,000 years ago, the Kachemak Culture spread throughout much of Cook Inlet. The Marine Kachemak inhabited the lower shores and were closely linked to people from the outer Kenai coast and Kodiak Island. In contrast, the Riverine Kachemak were more influenced by Bristol Bay and northern coastal communities. The Dena’ina people arrived in Southcentral Alaska between 1,500 and 1,000 years ago, migrating from the interior. They are the only Alaskan Athabaskan group to live on the coast. In 1778, Captain James Cook became the first European to explore and document the shores of the inlet, naming many significant geographical features. In 1787 or 1788, Russian fur traders from the Shelikhov-Golikov Company established a trading post called Aleksandrovskaia at English Bay, present-day Nanwalek. Around the same time, traders from the Lebedev-Lastochkin Company set up a trading post named Pavlovskaia at the mouth of the Kenai River. In 1789, English ships under Nathaniel Portlock and George Dixon revisited the inlet. They stayed for nearly a month, successfully traded for furs, and discovered coal beds at Port Graham. In 1794, Captain George Vancouver surveyed the inlet, correcting the latitude on Cook’s charts. He also determined that it was not a great river, as Cook had described. Consequently, the name was changed from Cook River to Cook Inlet.

William H. Dall visited Grewingk Glacier in 1880, 1892, and 1895. His mapping results were incorporated into U S Coast and Geodetic Survey charts. In 1899, Dall returned with geologist Grove Karl Gilbert during the Harriman Expedition, where Gilbert provided a detailed description of the glacier. The glacier’s ice front currently calves into an expanding pro-glacial lake, approximately 2 miles (3.2 km) long. Between 1986 and 2014, the glacier retreated 0.9 miles (1.5 km), or about 164 feet (50 m) per year. The glacier slope increased 1.5 miles (2.4 km) above the terminus, leading to more crevassing, suggesting the lake will end at this point and potentially reduce the retreat rate. In the fall of 1967, the loss of glacial ice possibly triggered a massive landslide of 2,966 million cubic feet (84 million cubic meters) of rock and debris, creating a tsunami that swept across the forefield of Grewingk Glacier. Several named glaciers on the southeastern side of Kachemak Bay approach but no longer reach tidewater. From south to north, these include the remnants of the Southern Glacier, which drains into Tutka Bay; Doroshin and Wosnesenski Glaciers, draining into Neptune Bay; Grewingk Glacier; Portlock Glacier, draining just north of Mallard Bay; Dixon Glacier, draining via the Martin River; Kachemak Glacier, draining into Bradley Lake; Dinglestadt Glacier, draining via the Sheep River; and Chernof Glacier, draining via the Fox River. These are the westernmost glaciers on the Kenai Peninsula. Between 1950 to 2005, at least 27 glaciers in the Kenai Mountain icefields retreated, with the Grewingk Glacier retracting by 1.5 miles (2.4 km). Read more here and here. Explore more of Grewingk Glacier and Kachemak Bay here: