McIver Bight, Unalaska Island

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McIver Bight, Unalaska Island

by | Feb 28, 2020

McIver Bight is a cove on the southwestern coast of Unalaska Island, 825 miles (1,330 km) southwest of Anchorage and 38 miles (62 km) southwest of Dutch Harbor, Alaska. The local name was first published in the 1944 Aleutian Coast Pilot. McIver Bight forms the northern part of Kashega Bay that is separated from Pumicestone Bay by Kashega Point. This Russian name was given and first published in 1792 by Lieutenant Sarichev of the Imperial Russian Navy as “Zaliv Koshiginskoy” or “Koshigin Bay” in honor of Yefim Koshigin who spent the winter at Unalaska in 1763. Pumicestone Bay is named for the local pumice rock and was first published by the U.S. Bureau of Fisheries in 1888.

Pumice is a light colored igneous rock made of volcanic glass and characterized by being pitted with many cavities (known as vesicles) on the surface and inside. Despite the name, the the rocks in Pumicestone Bay are actually a type of scoria, another vesicular volcanic rock that differs from pumice in having larger vesicles, thicker vesicle walls and being dark colored and more dense. Pumice and scoria are created when super-heated, highly pressurized rock is violently ejected from a volcano. The unusual foamy configuration of the rock happens because of simultaneous rapid cooling and rapid depressurization. The depressurization creates bubbles by lowering the solubility of gases (including water and carbon dioxide) that are dissolved in the lava, causing the gases to rapidly come out of solution. The simultaneous cooling and depressurization freezes the bubbles in a matrix to create the vesicles.

On March 6, 2017, the fishing vessel Saint Dominick grounded in Pumicestone Bay. The engine room flooded within 10–20 minutes of the grounding, and the four crewmembers abandoned the vessel a short time later. None of the crew were injured, and no pollution was reported. There are over 180 known wrecks and groundings on or adjacent to the Alaska Maritime National Wildlife Refuge, but many more wrecks are not documented. Read more here and here. Explore more of Pumicestone Bay here:

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