Cook Inlet

Coordinates: 60°20′16″N 151°52′30″W / 60.33778°N 151.87500°W / 60.33778; -151.87500
Source: Wikipedia, the free encyclopedia.
Cook Inlet
Tikahtnu, Cungaaciq
  • Tikahtnu (
    Tanaina)
  • Cungaaciq (Alutiiq)
The navigational light at the southwestern tip of Elizabeth Island demarcates the boundary between Cook Inlet and the Gulf of Alaska
LocationSouth-central Alaska
Coordinates60°20′16″N 151°52′30″W / 60.33778°N 151.87500°W / 60.33778; -151.87500
River sourcesKnik River, Little Susitna River, Susitna River, Matanuska River
Max. length180 miles (290 km)
Surface area100,000 km2 (39,000 sq mi)

Cook Inlet (

Sugpiaq: Cungaaciq) stretches 180 miles (290 km) from the Gulf of Alaska to Anchorage in south-central Alaska.[1] Cook Inlet branches into the Knik Arm and Turnagain Arm at its northern end, almost surrounding Anchorage. On its southern end, it merges with Shelikof Strait, Stevenson Entrance, Kennedy Entrance and Chugach Passage.[2]

The Cook Inlet and both its arms are bodies of

Mount Redoubt, along with three other historically active volcanoes.[4] Cook Inlet provides navigable access to the port of Anchorage at the northern end, and to the smaller Homer port further south. Before the growth of Anchorage, Knik
was the destination for most marine traffic in upper Cook Inlet. Approximately 400,000 people live within the Cook Inlet watershed.

Geography

Clam Gulch

Cook inlet, along with the Kenai Peninsula, the Kenai Mountains, the Chugach Mountains, and

glacial till that was deposited.[5][6][7]

Cook Inlet exists in a subsidence zone which contains many faults, and is frequently prone to earthquake activity. The primary fault, the Aleutian Fault, is found in the nearby Aleutian Trench in the Gulf of Alaska, where a corner of the Pacific Plate is forced underneath Alaska at a 45 degree angle. Thus, most of the uplift force occurs along a line from Kodiak Island and up the Kenai Mountains to the Chugach mountains. The inlet lies in a region where the crust is wrinkled under this force and the tectonic forces push the ground downward. In 1964, a megathrust earthquake occurred when over 600 miles of the Aleutian fault ruptured, uplifting the Kenai Mountains 60 feet (20 meters) in under 5 minutes. With a magnitude of 9.2, the earthquake was the fourth largest ever recorded. It devastated Anchorage where much of downtown dropped several stories, and the mountains surrounding the Turnagain Arm subsided 8 feet (2.4 meters), submerging the towns of Portage and Girdwood, as well as long stretches of the Seward Highway.[8]

Locations of volcanoes near Cook Inlet

Because it lies along a

Drift River oil terminal
.

Cook Inlet has the fourth largest tidal range in the world. The shape of the inlet and its orientation with respect to the lunar orbit causes the tide to come in and go out very rapidly. As the inlet narrows, the speed of the water increases, creating very powerful currents with speeds of up to 6 knots (7 miles per hour). While lined with large areas of silt, the central and upper inlet is filled with narrow troughs that may be 150 to 300 feet (50 to 100 meters) deep. These, along with the tides, provide a challenge to ships navigating through the waters.

Gyre, which affects the climate and keeps the temperatures in the Cook Inlet region fairly moderate compared to the extremes found in other parts of the state.[14]

History

Turnagain Arm

The inlet was first explored and settled by

Kiakhta
.

Other Europeans to visit Cook Inlet include the 1778 expedition of James Cook, its namesake, who sailed into it while searching for the Northwest Passage. Cook received maps of Alaska, the Aleutians, and Kamchatka during a visit with Russian fur trader Gerasim Izmailov in Unalaska, and combined these maps with those of his expedition to create the first Mercator projection of the North Pacific. The inlet was named after Cook in 1794 by George Vancouver, who had served under Cook in 1778. Turnagain Arm was named by Cook, "turnagain" being a moniker he had used before, at his annoyance at having to turn around after exploring another dead end.

Upon reaching the head of Cook Inlet, Cook was of the opinion that both Knik Arm and Turnagain Arm were the mouths of rivers and not the opening to the Northwest Passage. Under orders by the

Ship Creek and encountered the local Natives for the first time when two men approached in kayaks, invited them to come ashore. Under Cook's orders, William Bligh, of HMS Bounty fame, organized a party to travel up Knik Arm. Bligh served as Cook's Sailing Master on this, his 3rd and final voyage, the aim of which was discovery of the Northwest Passage
. After meeting with some local Dena'ina, Bligh returned to report Knik Arm indeed led only to a couple of rivers.

Cook sailed up Turnagain Arm in his ship, HMS Resolution, finding it impossible to navigate against the strong currents and mudflats, and got stuck on a sandbar when he tried to get back out, having to wait for the tide to come in and free his ship. He never actually confirmed it led to a river, which led to a decade of massive speculation until George Vancouver returned to finish the map. Having been in a bad mood since first agreeing to explore the area, and as a result of this frustration, the second body of water was given the disingenuous name "Turn Again". Early maps label Turnagain Arm as the "Turnagain River".[16]

Fox River delta at low tide in Kachemak Bay

The SS Farallon was a wooden Alaskan Steamship Company liner that

Eklutna
village are the descendants of the residents of eight native villages around upper Cook Inlet.

During the

Girdwood and Portage dropped as much as 8 feet (2.4 m) by subsidence and subsequent tidal action. Both hamlets were destroyed. Girdwood was later relocated inland and Portage was abandoned. About 20 miles (32 km) of the Seward Highway
sank below the high-water mark of Turnagain Arm; the highway and its bridges were raised and rebuilt in 1964–66.

Communities

Most of Alaska's population is in the Cook Inlet area, with highest concentration in

Tyonek, Alaska
, some oil camps, and many seasonal fishing camps.

Resources

Oil Rig and Packraft on Cook Inlet

Shell in 1964, and newest of which is the Osprey platform installed by Forest Oil in 2000. Most of the platforms are operated by Union Oil, which was acquired by Chevron in 2005. There are also numerous oil and gas pipelines running around and under the Cook Inlet. The main destinations of the gas pipelines are to Kenai where the gas is primarily used to fuel commercial fertilizer production and a liquified natural gas (LNG) plant and to Anchorage where the gas is consumed largely for domestic uses.[19]

Alaska has approximately half the known coal reserves in the U.S. For decades, there has been a proposal to build a large coal mine (the

America's Ten Most Endangered Rivers of 2007, based on the threat of this mine.[20]

The bore appears as a wall of turbulent water

Turnagain Arm is one of only about 60 bodies of water worldwide to exhibit a

spring tides and opposing winds. Turnagain Arm sees the largest tidal range in United States, with a mean of 30 feet (9.1 m), and the fourth highest in the world, behind Bay of Fundy (38 ft, 11.7 m), Ungava Bay (32 ft 0 in, 9.75 m), and Bristol Channel (31 ft, 9.6 m).[21] The ocean's natural 12-hour 25-minute tidal cycle is close to Turnagain Arm's natural resonance frequency, which then reinforces the tide similar to water sloshing in a bathtub. Tidal fluctuations in the main body of Cook Inlet, while not as extreme as the shallow and narrow Turnagain Arm, regularly reach 25 feet (7.6 m) or more and exhibit currents in excess of 5 knots (9.3 km/h; 5.8 mph) at full tidal flow. The inlet and its arms have been proposed as a potentially attractive site for the generation of tidal power.[22][23]

The mouth of Turnagain Arm at low tide in winter; thousands of icebergs lie stranded on vast plains of glacial silt

Turnagain Arm and Knik Arm are known for large areas of silt. At low tide, much of this is exposed, making marine navigation difficult. Historically, ships and boats designed for the area had a relatively flat bottom with a modest centerboard and absence of a large keel because the boats would occasionally become beached at low tide either on purpose or by accident. This design allowed the craft to support its weight on land without sustaining any serious damage to its structure. An example of this design is the Nomad, a much photographed fishing boat once owned by Joe Reddington which has sat on a mudflat near Knik for several decades.

These mudflats can also be dangerous to walk on, exhibiting quicksand-like characteristics, and have claimed the life of at least four people who have wandered out on them, usually tourists, with many more being rescued every year.[24][25][26]

Port of Anchorage, which is served by major container ship
companies and other carriers.

Conservation

View across Cook Inlet at low tide from downtown Anchorage, Alaska (September 2005)

The Cook Inlet

Killer whales commonly feed on belugas in the Cook Inlet, driving them to the upper part of the inlet where they often seek refuge in the shallower waters of the arms.[30]

In 2000, the US National Marine Fisheries Service listed the Cook Inlet beluga whale population as depleted and began development of a conservation plan. On October 22, 2008 the Cook Inlet beluga whale was put onto the endangered species list.[31] Cook Inlet activities include commercial fishing, oil and gas development, release of treated sewage, noise from aircraft and ships, shipping traffic, and tourism. However, it is not known what impact these activities had on the beluga whale population.

The Coastal Marine Institute at the University of Alaska Fairbanks's School of Fisheries and Ocean Sciences working with the U.S. Department of the Interior's Minerals Management Service (MMS), began a three-year project in 2003 focusing on the water circulation in Cook Inlet.[32]

Cook Inletkeeper, a member of the Waterkeeper Alliance, began in 1994 when a group of Alaskans became concerned about the rapid ecological changes in the inlet. The group formally incorporated the following year using settlement proceeds from a Clean Water Act lawsuit against Cook Inlet oil and gas producers.[33] Their stated mission is to "protect Alaska's Cook Inlet watershed and the life it sustains," with a focus on clean water, healthy habitat, local economies, and energy. They are based in Homer.[34]

See also

Cook Inlet seen from the mouth of Kachemak Bay, with Mount Iliamna in the background

Notes

  1. ^ "Cook Inlet, Alaska". Archived from the original on June 11, 2007. Retrieved 2007-02-03.
  2. ^ United States Coast Pilot 9. "Coast Pilot 9 – 33rd Edition, 2015". Office of Coast Survey. page 182. Retrieved 28 November 2015.{{cite web}}: CS1 maint: numeric names: authors list (link)
  3. ^ Summary of Quaternary geology of the Municipality of Anchorage, Alaska
  4. ^ "Cook Inlet-South Central Alaska map and volcano list". Alaska Volcano Observatory. Retrieved 2007-02-03.
  5. ^ Summary of Quaternary geology of the Municipality of Anchorage, Alaska
  6. ^ USGS Detailed Geologic Map View of Anchorage, AK
  7. ^ "Alaskan mountains". Encyclopedia Britannica (Online ed.). Retrieved January 24, 2024.
  8. ^ USGS M9.2 Alaska Earthquake and Tsunami of March 27, 1964
  9. ^ "Augustine, Cook Inlet, Alaska". Archived from the original on 2007-02-04. Retrieved 2007-02-03.
  10. ^ "Historic Earthquakes – Cook Inlet, Alaska". Retrieved 2007-02-03.
  11. ^ CMI Cook Inlet Surface Current Mapping
  12. ^ Mapping Cook Inlet Rip Tides Using Local Knowledge and Remote Sensing
  13. ^ Alaska Bore Tide
  14. ^ AMS - Glossary of Meteorology
  15. ^ Aunt Phil's Trunk: Bringing Alaska's history alive! Volume 3 by Laurel Bill, Phyllis Carlson – Aunt Phil's Trunk LLC 2016 pp. 1–5
  16. ^ Captain Cook: Master of the Seas by Frank McLynn, Yale University Press, 2011
  17. ^ Lloyd, Steve K. "The Farallon Shipwreck Project". WSU Press. Archived from the original on 28 July 2011. Retrieved 10 June 2011.
  18. ^ "Cook Inlet Oil and Gas". Archived from the original on 2007-02-05. Retrieved 2007-02-03.
  19. ^ "Kenai, Alaska plant". agrium.com. Archived from the original on October 14, 2006. Retrieved 2007-02-03.
  20. ^ "Chuitna Coal Mine". inletkeeper.org. Archived from the original on July 1, 2007. Retrieved 2007-05-13.
  21. ^ "Frequently Asked Questions – Tide Predictions and Data". NOAA. Retrieved 2008-09-10.
  22. ^ "Tidal Energy". Ocean Energy Council. Archived from the original on 2008-05-13. Retrieved 2008-11-11.
  23. ^ Salequazzaman, M.; Newman, Peter; Ellery, Mark; Corry, Brendan. "Prospects of electricity from tidal power in coasl regions of Bangladesh" (PDF). Journal of Bangladesh Studies. Murdoch University, Perth, Western Australia. Archived from the original (PDF) on 15 February 2012.
  24. ^ Lemagie, Sarah (May 5, 2005). "Unusual Turnagain Arm tide has attractions and dangers". Anchorage Daily News. Archived from the original on May 5, 2005.
  25. ^ Theriault Boots, Michelle (June 25, 2013). "Man who died on mud flats was Army attorney, outdoorsman". Anchorage Daily News. Archived from the original on February 1, 2014.
  26. ^ Thiessen, Mark (May 24, 2023). "'Mother Nature has no mercy': Man gets stuck waist-deep in Alaska mud flats, drowns as tide comes in". AP News. Associated Press. Retrieved January 24, 2024.
  27. ^ "Management and Recovery of Cook Inlet Beluga Whales". NOAA Fisheries. Retrieved 2007-02-03.
  28. ^ "The IUCN Red List of Threatened Species". IUCN Red List of Threatened Species. Retrieved 2018-10-28.
  29. ^ Nmfs.Noaa.gov[dead link]
  30. .
  31. ^ "Beluga Whale". NOAA Fisheries. Retrieved January 24, 2024.
  32. ^ Johnson, Mark; Okkonen, Steve; Proshutinsky, Andrey; Proshutinsky, Tatania. "Water and Ice Dynamics in Cook Inlet, Alaska". Institute of Marine Science. Retrieved 2007-02-03.
  33. ^ "Cook Inletkeeper - History". Cook Inletkeeper. 24 March 2017. Retrieved 2018-07-30.
  34. ^ "Cook Inletkeeper - Our Work". Cook Inletkeeper. 22 March 2017. Retrieved 2018-07-30.

External links