Tigalda Sea Stack, Krenitzin Islands

Tigalda Sea Stack, Krenitzin Islands

by | Nov 19, 2023

Sea stacks are a common feature on the Gulf of Alaska coast, particularly along the Alaska Peninsula and the Eastern Aleutian Islands, about 200 miles (323 km) southwest of Sand Point and 64 miles (103 km) east-northeast of Dutch Harbor, Alaska. Tigalda Island is in the Krenitzin Islands in the Eastern Aleutians. There are 8 named islands in the group situated between Unalaska Island to the southwest and Unimak Island to the northeast. All are managed as part of the Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge. The Krenitzins were probably named by Captain Mikhail Tebenkov in 1852 for Captain Lieutenant Peter Kuzmich Krenitzin who explored and mapped over 30 islands in the Aleutians between 1768–69.

The south side of Tigalda Island is exposed to the full force of waves generated in the Gulf of Alaska where the rocky coast is subject to severe erosion. A sea stack is an erosional geological landform consisting of a steep and often vertical column of rock near a wave-exposed coast. Sea stacks are formed when part of a headland is eroded by hydraulic action, which is the force of the water driven by wind waves. The water weakens cracks in the headland, eventually causing a collapse, forming free-standing stacks or an isolated islet. Eventually, erosion will cause the stack to collapse, leaving a wave-washed platform or submerged reef. Sea stacks can provide important nesting habitat for seabirds, particularly for bald eagles.

The bald eagle (Haliaeetus leucocephalus) is a bird of prey found near bodies of water that provide access to an abundant food supply and nesting habitat. The bald eagle is an opportunistic feeder that subsists mainly on beach carrion and fish. Live fish are caught directly from the water by dramatic aerial maneuvering and diving talons-first into the water without fully submerging. This sea eagle builds the largest nest of any North American bird and the largest tree nests ever recorded for any animal species. Along the coast of the Alaska Peninsula and the Aleutian Islands where there are no trees, the bald eagle nests on the ground. Because of various terrestrial predators including rats, foxes and bears, the preferred location for a ground nest is on sea stacks that afford excellent visibility and defensive isolation. Read more here and here. Explore more of Tigalda sea stacks here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2022 (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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