Ch.7: weathering & Ch.8: Sedimentary Rocks
Weathering: the breakdown of minerals and rocks by mechanical (physical), biological, or
Erosion: the transport of weathered material
Types of Weathering
Physical weathering: mechanical breakdown of minerals and rocks w/o a change to its
chemical composition. (Fig. 7.6)
i) Abrasion: grain to grain contact
Freeze-thaw: water in cracks freezes overnight and expands the next day. Repeated
expansions widen fractures (Fig. 7.7)
iii) Hydraulic action: The energetic force of moving water can break down rock and
Pressure release: Tectonic uplift and erosion over time removes overburden. Expansion of
once deeply buried rock results in joints (fractures). (Fig. 7.4)
-Pressure release also occurs with plutonic rocks, forming sheet joints
(curved joints). (Fig. 7.5)
Biological weathering: disintegration of rock physically or chemically by loving organisms.
Chemical weathering: the chemical decomposition of minerals in rock.
-New sedimentary minerals may form as a weathering product and some compounds
will be dissolved in water.
Hydrolysis: The chemical weathering silicate minerals by weakly acidic waters.(Fig. 7.10)
Oxidation: The chemical weat