EARTHSC 2GG3 Lecture 7: Lecture 7
12 Jan 2017
School
Department
Course
Professor
Document Summary
Definition: nearly vertical downward (cid:373)o(cid:448)e(cid:373)e(cid:374)t of earth(cid:859)s surfa(cid:272)e. 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. Definition: an irregular landscape containing many depressions. Some rocks dissolve in the vicinity of water. Karst is most evident in areas of limestone because this is the most common of the dissolving rocks. Water containing carbon dioxide is acidic and thus aids in the dissolution process. Chemical reactions leading to dissolution: water + carbon dioxide = carbonic acid, carbonic acid + limestone = calcium carbonate. Limestone dissolution can result in the lowering of a surface by 1 cm per decade.
