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Chemical Weathering: Hydrolysis & Hydration. Hydrolysis. Chemical weathering involving rainwater and some minerals in rocks (feldspar + ferromagnesian) React with feldspar and mica to form clay that crumbles easily and washed away
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Hydrolysis Chemical weathering involving rainwater and some minerals in rocks (feldspar + ferromagnesian) React with feldspar and mica to form clay that crumbles easily and washed away Clay are soft and expands in volume; causing granular disintegration Iron in mica oxidised to form reddish-brown iron oxide Resistant minerals like quartz are left unaltered and remain as sand Reason why sedimentary rocks are formed by quartz and clay Common in hot, wet regions
Hydration Swelling of rock minerals when they absorb water Swelling causes stress in rocks, forcing grains apart Anhydrous calcium sulphate absorbs water to form hydrated calcium sulphate (gypsum) Repeated wetting and drying of minerals led to flaking of rocks; granular disintegration Reversible change as mineral composition remains unchanged
Pressure release Source: Interactive Geography Sec 3 textbook