WeatheringPhysical weatheringChemical weatheringErosional ProcessesSheet ErosionMass ErosionLinkagesUndercuttingGEO 155 1st Edition Lecture 23Last Lecture Glacial LandformsOutline of Current LectureI. Erosion on Slopesa. Prelude to Erosion Weatheringb. Slope Erosion Processesc. Links between Erosional Processes and Formi. Simple Exampleii. Complex Exampled. SlidesCurrent LectureWeatheringPhysical weathering- Break down into smaller pieces- Frost-shattering – in environments with enough precipitation and temperature fluctuation above and below the freezing point of water allows liquid water to freeze in cracks of rock, expands the rock’s surface, and breaks the rockChemical weathering- Involves a chemical alteration- Solution of limestone dissolved by acids – even slightly acidic rainwater creates rectangular cracks under the surface of the rock, water passes through the cracks dissolving rock especially at the These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.intersections of the rectangles gradually opening up the rock collapsing it downward to form a “sink hole”Erosional ProcessesSheet Erosion- Soil particles carried downhill by overland flowMass Erosion- Material not carried by water- Rapid: rock-fall, landslide- Slow: creepo Water moves into soil swelling the surface or soil freezes and expands the surface, particles lifted to new expanded level until the soil thaws and then gravity pushes the particle downhill from its original positionLinkages Undercutting - Weathering concentrated at base of the slopeo Water wears away the bottom of the slope, gravity causes rock-fall leaving a steep clifo When a rock structures has layers of hard and soft rocks, the soft rock layers erode quicker so the hard rock layers above break of making a steep clif with a “staircase” appearance- Geomorphologist Schumm looked at the Badlands in South Dakota and noticed two types of structures:1. Straight slopes made of Brule formation rock typea. Weathers into fine particles leading to:i. Overland flowii. Parallel sheet erosion (evenly eroded)b. Occurs in arid and shallow soil/vegetative areas2. Convex shaped slopes of Chadron formation rock typea. Weathers into coarse particles leading to:i. Infiltrationii. Creep1. Particles shift down to replace lost particles2. Net concentration of erosion on top of slopeb. Occurs in denser, humid areas3. To measure the erosion, Schumm drove metal stakes into the ground and found the distance of erosion to be even for Brule formation and more erosion toward the top of slopes in Chadron
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