68953-Ch17_IM

68953-Ch17_IM - Chapter 17: Solution Processes and Karst...

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Chapter 17: Solution Processes and Karst Topography TOPICS The Impact of Solution Processes on the Landscape Solution and Precipitation Caverns and Related Features Karst Topography Hydrothermal Features Hot Springs Geysers Fumaroles Hydrothermal Features in Yellowstone People and the Environment: Sinkholes in Florida KEY TERMS carbonic acid (p. 515) cavern (p. 516) collapse doline (p. 519) disappearing stream (p. 521) dissolution (p. 515) fumarole (p. 523) geyser (p. 522) hot spring (p. 521) hydrothermal activity (p. 521) karst (p. 517) sinkhole (p. 518) speleothems (p. 517) stalactite (p. 517) stalagmite (p. 517) swallow hole (p. 521) tower karst (p. CHAPTER OUTLINE I. The Impact of Solution Processes on the Landscape A. Underground water is almost totally ineffective in terms of hydraulic power, corrosion, and other kinds of mechanical erosion. 1. Largely unchanneled, thus diffused. 2. Tends to move slowly. B. Effective shaper of landscape because of its chemical action. 1. Causes some widespread and distinctive results in surface topography. a) By working as solvent, dissolving certain rock-forming chemicals. b) By creating hydrothermal features. II. Solution and Precipitation A. Water is usually a poor solvent, but underground water is usually laced with chemical impurities, making it a weak solution of carbonic acid. 1. Contains dissolved carbon dioxide gas. 2. Dissolution Processes a) Dissolution weathers/erodes all rocks, but particularly affects carbonate sedimentary rock, especially limestone. b) Limestone is durable above because resistant to mechanical erosion, but vulnerable underneath because soluble. 238
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c) Gypsum and chalk undergo similar reactions, and dolomite dissolves almost as quickly. 3. Role of Bedrock Structure a) Bedrock structure plays a role in dissolution. b) The more cracks and joints, the more groundwater can penetrate. 4. Precipitation Processes a) Minerals in solution can then precipitate out, such as when reduced air pressure in an open cavern induces precipitation of the minerals out of water, or when hot springs are exposed to open air. b) Hot water is generally a much better solvent than cold, except regarding calcium carbonate, which dissolves better in cool than warm water. III. Caverns and Related Features A. Cavern —large, open underground areas occurring in massive limestone depositions at or near the surface. 1. Two stages of cavern formation: a) Initial excavation, when water dissolves the limy bedrock and leaves voids. b) Decoration stage, when water leaves behind the compounds it had been carrying in solution. (1) Speleothem —a feature formed by precipitated deposits of minerals on the wall, floor, or roof of a cave. (a)
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This note was uploaded on 06/06/2010 for the course EC 11 taught by Professor All during the Spring '10 term at UCLA.

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68953-Ch17_IM - Chapter 17: Solution Processes and Karst...

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