Ground-Ice Wedges: The Dominant Form of Ground-Ice on the North Coast of Alaska
Ground-Ice Wedges: The Dominant Form of Ground-Ice on the North Coast of Alaska
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地冰楔：阿拉斯加北海岸地冰的主要形式
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E. D. K. Leffingwell;P. S. Smith;GROUND
众所周知，北极和亚北极地区的地面永久冻结到很深的地方，只有上面几英尺的地方在夏天解冻。几乎所有的观察者都报告说，在地面下存在着或多或少的透明冰体，通常直接低于年度解冻的极限。通常，冰被描述为存在于具有一定厚度和横向范围的水平层中，但作者在阿拉斯加北岸的观察表明，至少在那里，地冰主要存在于垂直楔形的网络中，围绕着冻原形成的孤立体。虽然这种冰的形式是研究地区的主要冰，但并不认为它是唯一的一种，也不认为它的形成理论适用于每一种情况。似乎可以肯定的是，有几种不同类型的地面冰，每一种都以不同的方式起源。在1914年夏天，人们拍摄了几十张冰的照片，但大多数后来都被水损坏了，所以作者不得不主要依靠草图，这些草图往往是匆忙完成的。幸运的是，P.S.史密斯，美国地质调查局，有，几年前，获得了Noatak河上的地面冰的照片，其中一张照片说明了楔形冰，这是本文的主题（图2和图3）。（第一卷，第2段）。在研究冻原的形成过程中遇到的主要困难来自于不正确的曝光。由于地面的材料只能通过霜冻来加固，短时间暴露在夏季的空气中会导致塌陷，从而掩盖细节。只有在波浪或河流的作用破坏了堤岸表面，以致大块体断裂的地方，才形成良好的暴露面。作为
It is a widely known fact that the ground in Arctic and subArctic regions is permanently frozen to a great depth, only the upper few feet thawing in summer. Nearly all observers have reported the presence of bodies of more or less clear ice underlying the surface of the ground, usually immediately below the limit of annual thawing. Ordinarily the ice is represented as existing in horizontal beds of some thickness and lateral extent, but the observations of the writer upon the north shore of Alaska show that there, at least, the ground-ice occurs chiefly in a network of vertical wedges, surrounding isolated bodies of the tundra formation. Although this form of ice is the dominant one in the area studied, it is not held that it is the only one, nor that the theory of its formation will fit every case. It seems quite certain that there are several different kinds of ground-ice, each one having originated in a different way. During the summer of 1914 several dozen photographs of the ice were made, but most of them were damaged later by water, so that the writer has to depend chiefly upon sketches which were often hastily made. Fortunately Mr. P. S. Smith, of the United States Geological Survey, had, some years ago, secured photographs of ground-ice on the Noatak River, and one of these photographs illustrates the wedge-form ice which is the subject of this paper (Figs. I, 2). The chief difficulty encountered in the study of the tundra formation arises from faulty exposures. The ground being of material only consolidated by frost, a short exposure to the summer air will cause slumping and consequent masking of the details. It is only where wave or river action has undermined the face of a bank, so that large blocks break off, that good exposures are formed. As