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DRAINAGE PROPERTIES OF GLACIER ICE STRUCTURES WITHIN GLACIERS Foliation is irregular lenticular banding characterized by differences in grain size or crystallinity, or by air bubbles and dirt content. Usually strongly developed near the lateral margins of valley glaciers owing to strong stress between valley walls and ice. Also develops near the glacier bed and between ice streams. Ogives are surface swells and swales on the glacier surface. They generally occur beneath ice falls and are formed either by differential melting of darker (summer) and lighter (winter) bands of ice (banded ojives), or varying thickness of ice flowing over ice falls (swell-and-swale ojives). The relief of ogives becomes less marked down-glacier. Crevasses are deep, steeply inclined, open fractures created in brittle surficial ice of a flowing glacier undergoing extension. Most are linear to gently curvilinear, a few 10 to 1000 of meters long, and many meters deep. In warm valley glaciers few are more than 30 m deep, but in cold glaciers they can be much deeper marginal - point up glacier and produced by large differences in flow velocity. Rotate and close over time. . transverse - generally concave down glacier and produced by acceleration of flow (ice falls). Become straighter over time. splaying - reflect radial splayed pattern and formed where an ice stream spreads out or overrides a positive relief feature on the floor of the glacier. terminal splaying
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