Weathering Processes Karst Topography and Landscapes Mass Movement Processes

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1 GEO 101: PHYSICAL GEOGRAPHY Chapter 13: Weathering, Karst, and Mass Movement Weathering Processes Karst Topography and Landscapes Mass Movement Processes

2 Weathering Processes Processes that disintegrate rock into mineral particles or dissolve them in water Physical weathering Chemical weathering

3 Physical Weathering (Mechanic Weathering) Frost Action (freeze-thaw action) When water freezes, its volume expands ~9%. Expansion creates mechanic forces. Crystallization Dissolved minerals in the water evaporates and grow crystals (e.g., salt), breaking the rocks Mostly in Arid or semiarid environments Pressure-Release Jointing Erosion and transportation reduce the weight of in some areas isostatic uplift Creating fractures and joints amenable for furthering weathering

4 Chemical Weathering Hydration and Hydrolysis Hydration combination with water, involves little chemical change Hydration expansion Dehydration condensation Hydrolysis Minerals chemically react with water. Feldspar (K, Al, Si, O) + carbonic acid + water residual clays + dissolved minerals + silica

5 Oxidation Chemical Weathering Metalic elements combine with oxygen to form oxides (rusting) Iron (Fe) + Oxygen (O 2 ) iron oxide (Fe 2 O 3 ) Carbonation and Solution Minerals dissolve into a solution; e.g., NaCl Water dissolves CO 2 forming carbonic acid (H 2 CO 3 ) calcium carbonate + carbonic acid and water calcium biocarbonate

6 Factors Influencing Weathering Processes Characteristics of the bed rocks Climatic elements Geographic orientation Vegetation Ground water and water movement

7 Weathering Processes Factors Influencing Weathering Processes Characteristics of the bed rocks: hard or soft, soluable or insoluble, broken or unbroken Joints: fractures or separations in rock increase the surface area of rock exposed to physical and chemical weathering Climatic elements: precipitation, temperature, and freeze-thaw cycles Dry, cold climate physical weathering dominated Wet and warm climate chemical weathering Geographic orientation: face orientation controls the slope s exposure to Sun, wind, and precipitation Vegetation Ground water and water movement

8 Karst Topography and Landscapes Karst features: Develop from weathering of limestone landscapes Pitted, bumpy surface, poor surface drainage, and well developed channel underground Lands Covered with Sinkholes Circular depressions created by dissolution of carbonate Collapsed sinkholes and karst valley Caves and Caverns Subsurface dissolution Stalactite and stalagmites

9 Cavern Features Figure 13.20

10 Sinkholes Puerto Rico, giant telescope in a sinkhole Florida sinkhole Figure Figure 13.18

11 Karst Topography and Landscapes Necessary conditions for karst formation The Limestone formation contains > 80% calcium carbonates Complex patterns of joints for conducting water through subsurface drainage channels An air-containing zone between ground surface and water table Vegetation cover to supply organic acids e.g., Indiana, Kentucky, New Mexico, Florida

12 Mass Movement Processes Mass Movement All mass movements occur on slopes due to gravitational stress

13 Slope Mechanics and Form Figure 13.3 Controlling factors for downslope transportation: Slope angle (gravity) Forces of friction Inertia (the tendency of objects at rest to remain at rest) Cohesion of particles to each other

14 Mass Movement Processes Classes of Mass Movements Falls and Avalanches (rockfall( rockfall,, debris avalanches): induced by heavy rains, volcanic eruption, earthquakes Landslides: A sudden rapid movement of a large amount of soil or bedrock (not saturated with water) Flows: mud- and earth-flow (saturated with water), especially from barren mountain slopes during heavy rains Soil creep: A persistent, gradual mass movement of surface soil due to cycles of wetness and dryness.

15 Soil Creep Figure 13.27

16 Human-Induced Mass Movements Human-Induced Mass Movements (Scarification) highway roadcut, surface mining, building of shopping mall, high buildings, housing development

17 Human-induced Mass Movement Bingham Copper mine, Utah Figure 13.28

WEATHERING, EROSION, AND DEPOSITION PRACTICE TEST. Which graph best shows the relative stream velocities across the stream from A to B?

NAME DATE WEATHERING, EROSION, AND DEPOSITION PRACTICE TEST 1. The diagram below shows a meandering stream. Measurements of stream velocity were taken along straight line AB. Which graph best shows the