Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Weathering and Erosion
Document related concepts
Transcript
WEATHERING AND EROSION CHAPTERS 14 & 18 WEATHERING 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 • Oxidationelements in rock combine with oxygen, mostly in rocks with iron (rusting) TYPES OF CHEMICAL WEATHERING • Hydrolysisreaction 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 precipitationwater 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 • 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 • 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 452-453 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
