Unformatted text preview: Geology 1001
Chapter 16 – Weathering, Erosion, and Mass Wasting El Capitan, NM Rocky Mountains 1 Copenhagen Conservation Area, LA Processes that shape the Earth Weathering: process by which rocks are broken down at the surface Erosion: describes particle by particle movement Mass Wasting: single-event movement of a singlesegment of the land 2 Weathering Products: All rock fragments All soils Dissolved ions in solution Weathering: Quick Review (Ch. 5) Physical Weathering: big rocks mechanically fragmented or broken into smaller particles. Weathering: Quick Review (Ch. 5) Chemical Weathering: components of rocks are chemically altered or dissolved. 3 Agents of weathering: H2O Wind CO2 O2 Naturally-occurring acids Naturally- Controls on Weathering Rock Type: • minerals have different weathering rates. • some rocks are more prone to fracture Controls on Weathering Climate: Temperature Moisture Vegetation 4 Controls on Weathering Presence of soils: • Soils increase chemical and physical weathering. • Positive feedback: more weathering, more soils… soils… Controls on Weathering Length of exposure: • Longer exposure more weathering. Physical Weathering: Why do rocks break? Sed. rocks break along bedding planes. Mistaken Point, Newfoundland 5 Physical Weathering: Why do rocks break? Joints: fractures caused by compression Physical Weathering: Why do rocks break? Physical Weathering: Why do rocks break? Biological activity can break rocks 6 Physical Weathering: Why do rocks break? Frost wedging: expansion of water in cracks Physical Weathering: Why do rocks break? Exfoliation: large sheets break from outcrops Chemical Weathering Involves chemical reactions: Minerals are dissolved New minerals form Agents of chemical weathering: H2O, CO2, O2 7 Physical weathering enhances chemical weathering Yosemite N.P., CA. 8 Water and Weathering Quartz and feldspar are the most abundant minerals in granite. Quartz: not readily reactive or easy to dissolve Feldspar: reactive, weathers to clay minerals Water and Weathering 9 Feldspar alters to Kaolinite + H2O = Hydrolysis: loosen with water Hydrolysis: CO2 and weathering Carbonic Acid: most common acid on Earth Acid: “Speeds up” weathering up” 10 Carbon Dioxide and Weathering CO2 in the atmosphere dissolves in rainwater. CARBONATION Carbonic Acid and Weathering Water becomes slightly acidic Acidic water is reactive with feldspar Increases Kaolinite production Dissolves ions in solution 11 ...
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- Spring '07