WEATHERING AND EROSION CHAPTERS 14 & 18

WEATHERING WATCH BRAIN POP WATCH BRAIN POP The breaking down of rock 2 types: mechanical and chemical

MECHANICAL WEATHERING Rock is broken down by physical means Types: –Ice wedging (freezing and expansion) –Abrasion (collision of rocks by wind, water, or gravity) –Organic activity (plant roots, digging of animals)

ABRASION

CHEMICAL WEATHERING Rock is broken down due to chemical interaction with the environment

TYPES OF CHEMICAL WEATHERING Oxidation- elements in rock combine with oxygen, mostly in rocks with iron (rusting)

TYPES OF CHEMICAL WEATHERING Hydrolysis- reaction of minerals in rock to water, turns rock into clay

TYPES OF CHEMICAL WEATHERING Carbonation-carbon dioxide dissolves in water and creates carbonic acid (like in your soda!) This acid causes slow break down of rock

TYPES OF CHEMICAL WEATHERING Acid precipitation- water mixes with carbon dioxide and other air pollutants Weathers rock Air pollutants are often from burning fossil fuels

RATES OF WEATHERING DIFFERENTIAL WEATHERING: PROCESS BY WHICH SOFTER, LESS WEATHER-RESISTANT ROCK WEARS AWAY AND LEAVES HARDER, MORE WEATHER RESISTANT ROCK. Weathering occurs very slowly Rates depends on many factors: –Rock composition –Amount of exposure –Climate –Topography and elevation –Human activities –Plant and animal activities

ROCK COMPOSITION Rocks containing calcite weather the quickest Rate is determined by what material holds the sedimentary grains together

AMOUNT OF EXPOSURE More exposure=faster weathering Larger surface area exposed=faster weathering Fractures and joints create channels for more exposure

CLIMATE Areas with alternating hot and cold seasons have fastest rate of weathering Areas that are hot and dry have the slowest rate of weathering

SOIL WATCH BRAIN POP: SOIL WATCH BRAIN POP Mixture of minerals, gases, water, remains of dead organisms (humus) Soil profiles show layers of soil called horizons Humus Climate determines soil formation

SOIL PROFILE

EROSION WATCH BRAIN POP WATCH BRAIN POP Products of weathering are transported Soil erosion is caused by both natural and human activities (such as some farming) Erosion keeps crops from growing and can cause famine Roots of plants hold the soil in place Agents of erosion include: wind, water, gravity, glaciers

GRAVITY AND EROSION Mass movements caused by gravity:  rockfalls and landslides-very fast mvmt  mudflows and slumps-rapid mvmt  solifluction-slow, in cold regions  creep-very slow mvmt

LANDSLIDES

SLUMP Large block of soil and rock becomes unstable and moves downhill in one piece-occurs on very steep slopes

EROSION FROM WIND Sand grains get moved by a process called saltation (bouncing of grains by wind or water).

EFFECTS OF WIND EROSION Deflation-removal of top soil and rocks Deflation hollows-holes left from deflation Ventifacts-rocks with smooth surfaces from wind abrasion

WIND DEPOSITION Dunes are formed when the wind slows down and drops the sand it is carrying

WAVE EROSION As wind moves over the ocean, wind produces waves and currents that erode the coastline.

STRUCTURES FORMED FROM WAVE EROSION Sea cliffs Sea caves, arches, stacks Terraces See pgs

STACKS

SHORELINE EROSION Force of waves will break off rock and throw the pieces back on the shore creating abrasion (mechanical weathering) Shoreline is also chemically weathered-air and salt water are forced into cracks in the rock

BEACHES A deposit of sediment along the shore More sediment is deposited than removed

FARMING AND EROSION PREVENTION Contour Plowing Strip Cropping Terracing Crop Rotation These techniques help reduce the erosion caused by water flowing over the land.

CONTOUR PLOWING

TERRACING