冻胀丘
地下水受冻结地面和下部多年冻土层的遏阻,在薄弱地带冻结膨胀,使地表变形隆起,称为冻胀丘。内部有冰透镜体的称为冰核丘。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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