|
Sixtymile River (also "Sixtymile Creek") is a tributary of the Yukon River, which heads in the U.S. state of Alaska before crossing into Yukon, Canada. ==Geography== This stream heads in Alaska and has a length, after crossing into Canadian territory measured along the valley, of about , and following the windings of the stream, of about in total. Its fall, measured roughly with the barometer, from the boundary to the Yukon, amounts to , and the average grade of the valley to a little over to the mile. At the international boundary, it is a rapid winding stream averaging about in width and interrupted at frequent intervals by steep bars covered with only a few inches of water. The upper portion of the river from the boundary to California creek can hardly be considered a navigable stream even for small boats. Below California creek, the volume of water increases and the descent becomes less difficult, but bars and rapids continue almost to the mouth and no part of the river is easy to ascend. The tributary streams are small, as a rule, but two large streams, one draining the country to the west and one other to the south, come in within four miles of each other, nearly opposite Indian River, and these branches nearly double the volume of the main river. Towards its mouth, Sixtymile has an average width of from . Below Sixtymile, the Yukon contains many islands. The valley of Sixtymile is generally flat-bottomed, the flats varying from a to nearly in width. The sides are usually terraced and in places, the stream for long distances, has cut a secondary rock-walled channel, similar to that noticed on Indian river and Stewart River, through the bottom of its old valley. The country bordering Sixtymile River forms part of the Yukon plateau, a highland worn into rounded hills and long zigzag ridges, but containing no well-defined and continuous mountain ranges. At several points, high hills usually of andesite, project a few hundred feet above the general level.〔 Miller Creek enters Sixtymile about from its mouth. In addition to Miller Creek, Glacier, Gold, Little Gold, and Bed Rock creeks are all tributaries of Sixtymile. Sixtymile Butte, a prominent mountain above the headwaters of the stream, is of granite. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sixtymile River」の詳細全文を読む スポンサード リンク
|