Wikibooks: Historical Geology/Chemical weathering

• Format: Book
• Language: English
• Subjects: Carbonic acid
• Online Access: https://en.wikibooks.org/wiki/Historical_Geology/Chemical_weathering

Chemical weathering is the breakdown of rocks into sediment by chemical processes. The reader who does not appreciate chemistry may skip the chemical formulas in this article and simply note the results of the reactions as described in the summary section below. The results themselves cannot be skipped over understanding chemical weathering is essential to answering such basic questions as Why is [[sand]] mostly made of [[quartz]]? and Where does [[clay]] come from? =Agents of chemical weathering= The main agents of chemical weathering are Water . Some [[minerals]] such as [[rock salt]] will dissolve readily in water others such as [[pyroxene]] will also do so though at a much slower rate. Carbonic acid . Rainwater and groundwater are not pure water some of the molecules of water react with the carbon dioxide in the atmosphere (in the case of rainwater) or produced by bacteria and plant roots (in the case of groundwater) producing carbonic acid as follows [[H]] 2 [[O]] (water) + [[C]][[O]] 2 (carbon dioxide) → [[H]] 2 [[C]][[O]] 3 (carbonic acid) Oxygen . This is a highly reactive chemical and the only reason that there s so much of it about in the atmosphere is its constant production by biological processes and a shortage of things that it hasn t reacted with already. =Chemical weathering of common minerals= In this section we shall look at how some common minerals are affected by chemical weathering. We have arranged the list more or less in order from the minerals most susceptible to chemical weathering to the most resistant. Halite . Salt of course dissolves in water. This is why you are unlikely to see rock salt on the surface except in desert environments. Gypsum . This like halite is soluble in water similar remarks apply to it. Calcite . This you should recall from previous articles is the [[mineral]] forming [[limestone]] and its [[metamorphic]] counterpart [[marble]]. It can just dissolve in water it also reacts with carbonic acid as follows [[Ca]][[C]][[O]] 3 (calcite) + [[H]] 2 [[C]][[O]] 3 ...