Weathering Processes PDF

Geomorphic Processes: II. Exogenous II. Gradation Processes – Weathering, Mass Wasting, Erosion, Transportation and Deposition Geomorphic Processes:  Physical processes which create and modify landforms on the surface of the earth  Endogenous (Endogenic) vs.Exogenous (Exogenic) Pro...

Geomorphic Processes: II. Exogenous II. Gradation Processes – Weathering, Mass Wasting, Erosion, Transportation and Deposition Geomorphic Processes:  Physical processes which create and modify landforms on the surface of the earth  Endogenous (Endogenic) vs.Exogenous (Exogenic) Processes  Rock Cycle A. Endogenous Processes Endogenous Processes are large-scale landform building and transforming processes – they create relief. 1. Igneous Processes a. Volcanism: Volcanic eruptions Volcanoes b. Plutonism: Igneous intrusions 2. Tectonic Processes (Also called Diastrophism) a. Folding: anticlines, synclines, mountains b. Faulting: rift valleys, graben, escarpments c. Lateral Faulting: strike-slip faults Earthquakes evidence of present-day tectonic activity B. Exogenous Processes Also called Gradational Processes, they comprise degradation and aggradation – they modify relief a continuum of processes – Weathering Mass Wasting Erosion Transportation Deposition these processes are carried through by Geomorphic Agents: gravity, flowing water (rivers), moving ice (glaciers), waves and tides (oceans and lakes), wind, plants, organisms, animals and humans 1. Degradation Processes Also called Denudation Processes a. Weathering , b. Mass Wasting and c. Erosion and Transportation 2. Aggradation Processes a. Deposition – fluvial, eolian, glacial, coastal Relationship: Weathering Mass Wasting Erosion and Transportation Together, these processes are responsible for Denudation of Earth’s surface  WEATHERING Weathering is disintegration and decomposition of rocks in situ – no transportation involved produces regolith  More precisely, it involves the mechanical or physical disintegration and/or chemical decomposition that fragments rock masses into smaller components that amass on-site, before being moved by gravity or transported by other agents  The processes begin in microscopic spaces, cracks, joints, faults, fractures, lava vesicles and other rock cavities Types of Weathering: 1) Physical or Mechanical Weathering, 2) Chemical Weathering, and 3) Biological Weathering  Physical or Mechanical Weathering Disintegration and decay of rocks via weather elements: high temperatures, extreme cold and freeze-thaw cycles No change in chemical composition of rocks Exfoliation – due to thermal expansion/contraction and/or release of pressure when buried rocks are uplifted and exposed e.g., Exfoliation Dome (Stone Mountain, GA) and Exfoliation Sheets (Sierra Nevada) Frost Wedging Salt Wedging  Chemical Weathering decomposes rocks through a chemical change in its minerals Oxidation – important in iron-rich rocks – reddish coloration like rust Hydrolysis – igneous rocks have much silica which readily combines with water Carbonation and Solution – carbon dioxide dissolved in water reacts with carbonate rocks to create a soluble product (calcium bicarbonate)  Biological Weathering – plants and animals contribute to weathering.  Roots physically break or wedge rock  Lichens (algae and fungi living as single unit), remove minerals and weaken rock by releasing acids  Burrowing animals can increase weathering. Lichens Talus Cones in the Canadian Rockies Talus – pieces of rock at bottom of a rock fall Landslides Can cause much destruction A msssive 300-ton boulder blocks a road in Southern California La Conchita Landslide, January 10, 2005 Monterey Park Debris Flow, 1980 PCH near Pacific Palisades, November 1956 EROSION and TRANSPORTATION – Various Geomorphic Agents, associated Processes, and resulting Erosional Features Flowing Water – Fluvial Morphology Humid regions: Perennial streams and entrenched channels, rapids, waterfalls, plunge pools, potholes, meandering streams, bank erosion, oxbow lakes, etc.  Wind – Eolian Landscapes deflation hollows, ventifacts, yardang, etc Tides and Waves – Coastal Morphology Sea cliffs, sea caves, sea arches, sea stacks, wave-cut beaches, etc.. Moving Ice – Glacial Morphology glacial troughs (U-shaped valleys), hanging valleys, glacial lakes,. DEPOSITION – Various geomorphic agents, associated processes and resulting Depositional Features Fluvial – Humid regions: Braided streams, sand bars, floodplains (alluvium deposits), natural levees, distributaries, deltas Arid regions: Alluvial fans, bajadas, piedmont alluvial plains, playas, playa lakes, Salinas (salt flats) Eolian – Sand dunes (Barchans, Parabolic, Transverse, Longitudinal, Star), and sand sheets Coastal – Sea beaches and coral reefs Glacial – Alpine: Glacial drifts, tills, moraines (lateral, medial, end, terminal, recessional, and ground) Continental: Till plains, outwash plains, drumlins, eskers, kames, erratic