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单词 ice wedge
释义
ice wedge

Geology and Earth Sciences
  • Tapering, vertically layered mass of ice, about a metre wide at the top and extending downward for some 3–7 m. It results from contraction cracking of the ground during extreme cold, followed by water penetration from the active layer and subsequent freezing. It is characteristic of uniform sediment, such as river alluvium, under periglacial conditions.


Geography
  • In a periglacial landscape, a near-vertical ice sheet, tens to hundreds of metres long, tapering into the ground to depths of 12 m. Individual wedges usually meet another wedge orthogonally. Matsuoka (1999) Polar Geosci. 12 records an expansion of 16 mm across an ice wedge at –17 °C. Ice wedge casts are sediment-filled, fossil ice wedges; see Harris et al. (2005) Geomorph. 71, 3–4 for the ice-wedge casting processes.

    Ice-wedge networks

    form as ice fills the tension fractures resulting from cooling. They form in stable, aggrading or sloped surfaces, with winter temperatures from –15 °C to –35 °C. Modelled polygonal networks self-organize through interactions between fractures, stress, and re-fracture (Plug and Werner (2008) Permaf. & Periglac. Procs DOI: 10.1002/).


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