GEOG 1350 Lecture Notes - Lecture 7: Expansive Clay, Ground-Penetrating Radar, Mining
7 Dec 2016
School
Department
Course
Professor
Document Summary
Nearly vertical downward movement of earth"s surface. Not usually life-threatening but one of most widespread & costly hazards. The subsiding area can be a variety of shapes. Subsidence is often associated with the dissolution of limestone, marble, or gypsum. Some rocks dissolve in the vicinity of water. Water containing carbon dioxide is acidic and thus aids in the dissolution process. Water + co2 = carbonic acid (dissolves limestone) Carbonic acid + limestone = calcium carbonate: very slow, could lower surface 1cm/decade. The process produces empty voids over a range of sizes. Surface containing sinkholes is called karst plain. Depressions in the ground, could be very deep. Collapse sinkhole (formed by collapse of the surface -> begin as cave & collapse when it can"t support anymore, drier season) A system of caves may evolve as limestone voids continue to enlarge. Gen. term accumulation of caco3 precipitated from water in a cave. Water containing calcium carbonate drips from stalactite to stalagmite.
