thumb|300px|Turnagain Arm from [[Anchorage, Alaska|Anchorage.]]
Turnagain Arm (Dena'ina: Tutl'uh) is a waterway into the northwestern part of the Gulf of Alaska. It is one of two narrow branches at the north end of Cook Inlet, the other being Knik Arm. Turnagain is subject to climate extremes and large tide ranges.
Geography
thumb|Cook Inlet with Knik and Turnagain arms.
Turnagain extends in an east–west direction, and is between long. It forms part of the northern boundary of Kenai Peninsula, and reaches on the east to within of Passage Canal, a western branch of Prince William Sound. Turnagain is characterized by remarkably large tides of up to which are the largest tides in the United States. The flood tide often begins with a tidal bore especially on large tides with a strong east wind, which has a height of at times, and runs in from the west at a speed of an hour. At low tide, the arm becomes a broad mud flat, cut by the stream channels. Historically small steamers entered and left on high water though the practice is now rare since most if not all the places that they went are now connected by road.
The region adjacent to Turnagain Arm is very rugged. South Yuyanq' Ch'ex is the tallest mountain rising from the north side of Turnagain, and Mount Alpenglow the highest on the south side. Mountains rise precipitously on both sides of the arm and reach altitudes of . Their tops are ragged and bare. The timber rarely reaches higher than . The smaller valleys are narrow and steep, but the larger ones frequently show by their U-shaped cross section the former presence of glaciers. Glaciers may be still seen at a number of places. Chief among them are Portage Glacier, occupying the Portage Valley between the head of Turnagain Arm and Passage Canal, the two neighboring glaciers which form the headwaters of the Glacier River and Twentymile River, Explorer Glacier, and Skookum Glacier. Besides these, there are several smaller ones on tributaries of Glacier Creek. Turnagain Arm boasts the second highest tides in North America after the Bay of Fundy. These tides, which can reach , come in so quickly that they produce a wave known as a bore tide. Beluga Point Site, also known as ANC-054, is an archaeological location on the north shore of the Arm, while Alaska Wildlife Conservation Center is situated at the head of the Arm near the site of Portage.
Tributaries
Major tributaries of Turnagain Arm include the Twentymile River, Portage River, and Placer River. Minor tributaries include Resurrection Creek, Bear Creek, Sixmile Creek, and Glacier Creek, with their branches. Resurrection Creek flows into the south side of the arm about east of the main body of Cook Inlet, and with Sixmile Creek, farther east; with its various branches, it drains a large part of the northeastern portion of Kenai Peninsula. Resurrection Creek flows in a direction slightly east of north. The town of Hope is located near its mouth. Palmer Creek is its largest tributary. or "headwaters".
Cook spent ten days exploring the inlet named after him. He first sent William Bligh to scout the north arm, where he met with the Dena'ina Natives of the Eklutna area, who told him the name of the Knik Arm and that it was not the Northwest Passage, but rather an outlet for two rivers (the Knik and Matanuska Rivers). Cook then sailed south to scout the other arm, and in a bad mood after running the Resolution aground on a sandbar on his way back out of the shallow waters, called it "River Turnagain", having found no sign of the passage there either.
thumb|[[Alaska Railroad at Turnagain Arm]]
The mineral resources of the Turnagain-Knik region are notable for gold placers and the gold quartz lodes. From 1896 to 1898, a large number of placer claims were staked on the streams tributary to Turnagain Arm from the north, and on a few of these claims, notably those on lower Crow Creek, mining was carried out in subsequent years. The output of placer gold was derived from the Turnagain Arm slope of the mountains. Development work on gold quartz lodes was confined largely to the Turnagain Arm basin.
Geology
The eastern portion of Kenai Peninsula and the region about the head of Turnagain Arm present a succession of rocks, which as a whole are of remarkably uniform appearance and composition. They are of sedimentary origin and consist chiefly of fine-grained gray and bluish-black slates and gray arkoses. Interstratified with these, but in far less amount, are quartzose beds and occasional thin conglomerates. In a few places north of Turnagain Arm this series of rocks, called by Mendenhall "the Sunrise series", is cut by dikes of igneous rock of an aplitic or granitic character. These igneous rocks were not found in the region immediately south of the arm. The whole rock succession is closely folded, and the arkoses as well as the slates show cleavage, which is, however, much more perfectly developed in the slates. Immense deposits of gravel occur at a number of localities, but are especially noticeable in the valleys of Sixmile Creek, Resurrection Creek, and Kenai River. The flat-topped benches have an elevation of nearly above sea level around the lower end of Kenai Lake, and the same elevation was observed in the valleys of the streams mentioned. The bench gravels show a thickness of in the upper valleys, where they have been cut through by the streams. Evidences of a former period of glacial activity are seen on all sides in broad-bottomed U-shaped valleys, polished rock surfaces, and transported boulders. The shores of Turnagain Arm afford frequent proof of ice action in glacial markings and striated pebbles. Hanging valleys are not uncommon.
Dall sheep, hoary marmot, American black bear, American marten, and black-capped chickadee are noted.
See also
- Kenai Mountains – Turnagain Arm National Heritage Area