EARTHSC 2GG3 Lecture 9: lecture 9
14 Feb 2018
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Document Summary
Definition: nearly vertical downward movement of earth"s surface: the speed of subsidence can vary from very slow to rapid, the subsiding area can be a variety of shapes. It is not usually life threatening but is one of the most widespread and costly hazards. Subsidence is often associated with the dissolution of limestone, marble, or gypsum. Other causes: thawing of frozen ground, compaction of sediment, shrinking of expansive soil, earthquakes, deflation of magma chambers. Some rocks dissolve in the vicinity of water: karst is the most evident in areas of limestone because this is the most common of the dissolving rocks. From left to right is over 1000 years. Groundwater table: the underground depth at which point the ground is saturated with water (it is also called the water table). Often times there is a lot of water in caves depending on where the groundwater table is.
