Gastineau Channel ( Lingít: ''Séet Ká'') is a channel between the mainland of the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...

and Douglas Island in the

Alexander Archipelago The Alexander Archipelago (russian: Архипелаг Александра) is a long archipelago (group of islands) in North America lying off the southeastern coast of Alaska. It contains about 1,100 islands, the tops of submerged coastal m ...

of southeastern Alaska. It separates Juneau on the mainland side from Douglas (now part of Juneau), on Douglas Island. The first European to sight the channel was

Joseph Whidbey Joseph Whidbey FRS (1757 – 9 October 1833) was a member of the Royal Navy who served on the Vancouver Expedition 1791–95, and later achieved renown as a naval engineer. He is notable for having been the first European to discover and char ...

early in August 1794, first from the south and later from the west. It was probably named for John Gastineau, an English civil engineer and surveyor.

Characteristics

The channel is navigable by large ships, only from the southeast, as far as the Douglas Bridge, approximately . Between the bridge and

Juneau International Airport Juneau International Airport is a city-owned, public-use airport and seaplane base located seven nautical miles (8 mi, 13 km) northwest of the central business district of Juneau, a city and borough in the U.S. state of Alaska th ...

, approximately , it is navigable only by smaller craft and only at high tide. The channel is becoming increasingly unnavigable due to shallow water depths. The two principal causes for this are: #

Isostatic rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound ...

following the retreat of glacial ice sheets # Sedimentation and infilling of the Gastineau Channel by silty sediment produced by the Mendenhall Glacier and Mendenhall River. If current trends continue, Gastineau Channel may eventually become dry or unnavigable or both. During isostatic rebound, the Earth's lithosphere (crust) is slowly rising because of buoyant forces, following the removal of a large mass on the surface. This can be likened to an ice cube floating in a glass of water with a penny sitting on top. The weight of the penny makes the ice cube float lower, similar to the immense weight of a glacier on top of the lithosphere. When the penny (glacier) is removed, the ice cube (lithosphere) "rebounds" and floats slightly higher. In the geologic case, that scenario happens very slowly. Rates of isostatic rebound throughout SE Alaska vary from 0.1 to 1.5 inches/year depending on glacial history. The approximate rebound rate in the Juneau area is 0.25 to 0.5 inches/year.

References

Bodies of water of Juneau, Alaska Straits of Alaska Straits of the Pacific Ocean {{JuneauAK-geo-stub