Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ch 14 Weathering Two Types: 1. Physical or Mechanical 2. Chemical Mechanical Weathering • Rock is broken down into smaller pieces by physical means. • Agents: wind, water, ice, gravity, plants & animals. EXFOLIATION • Rocks break into curved sheets that peal away Ice Wedging • Water gets into cracks and freezes • Freeze/Thaw cycle splits rock ABRASION Wearing away of rocks by other rock particles WIND WATER ICE ROOT WEDGING Animals - Burrowing Chemical Weathering • Rock is broken down by chemical interaction with the environment. OXIDATION (rusting) • Elements combine with oxygen to form rust • Iron bearing rocks HYDROLYSIS: Minerals dissolve in water. HYDROLYSIS: Minerals decompose in water as hydrogen replaces cations in feldspar (turns into clay). LEACHING: Water carries dissolved minerals away, forms beds of aluminum (bauxite) Carbon Dioxide and water react to form carbonic acid...Carbonic acid “eats” limestone. CARBONATION: Limestone caves Acid Precipitation • Acids formed from the burning of fossil fuels combining with atmospheric water; bad for plants & structures. Factors that affect Rates of Weathering DIFFERENTIAL WEATHERING Softer, less-resistant rock wears away, leaving harder resistant rock behind. Bryce Canyon “Hoodoos” Rock composition • Sedimentary rocks containing calcites weather rapidly (limestone). • Quartz containing rocks are strong and weather slowly Surface area The more surface area per volume, the faster the rock’s weathering rate. Fractures and Joints • Increase surface area of rock • Allow weathering to happen faster Climates • Hot/Cold climates with freeze/thaw cycles have fastest weathering rates. • Hot/Dry climates weather the least. Topography • Elevation or slope of the land. • High Elevations – cold temp, ice wedging • Steep Slopes – gravity pulls rock down Human Activities • Mining • Construction Plants and Animals • Roots, Burrowing, Waste (Bat Guano)