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Weathering

Weathering. Weathering. The various mechanical and chemical processes that cause exposed rock to fall apart/decompose. Rock into sediments Rock into rust.

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Weathering

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  1. Weathering

  2. Weathering • The various mechanical and chemical processes that cause exposed rock to fall apart/decompose. • Rock into sediments • Rock into rust

  3. Weathering Factors Factors present and affecting weathering of rocks • Water • Temperature • Pressure

  4. Weathering Factors • Surface area • The more surface area • The more intense the weathering rate

  5. Weathering • Types of Weathering • 1. Mechanical/Physical • Rocks are broken into smaller pieces • Same original physical properties • No chemical change

  6. Types of Mechanical Weathering Frost Wedging ~ alternate freezing and thawing of water in rocks • due to changes in air temperature • Waterexpands in volume as it freezes by 7% to 9%. • Waterin the cracks of rocks freezes and expands. • Pressure against the crack walls …….. • Rocks spilt apart • .

  7. Weathering • Types of Weathering

  8. Types of Mechanical Weathering • Temperature change • rocks expand • Warm temperature Cold temperature • rocks contract • Alternate Tension (expansion) and Compression ( contraction ) Pressures • Atomic bonds break

  9. Weathering • Types of Weathering

  10. Types of Mechanical Weathering • Exfoliation (peeling)due to change in pressure byunloading. • Occurs in Igneous and metamorphic rocks _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ outer layers peel off “Exfoliation”

  11. Dome Rock • Colorado • Enchanted rock • Texas • Granite

  12. Weathering • Types of Weathering

  13. Types of Mechanical Weathering • Biological/Organic activity • Pressure force by plants and animals • Burrowing animals • plant roots • People !

  14. Review • Explain the type of weathering that is taking place. • Frost Wedging • What factors are present? • Water, Temperature, Pressure • Surface area • Explain the type of weathering that is taking place. • Exfoliation • What factor(s) is/are present? • Pressure • Surface area

  15. Review • Observe the weathered sidewalk. • Describe a possible type of mechanical weathering process. • Frost Wedging, • Thermal Expansion • Organic Activity

  16. Mechanical Weathering Lab • Lab

  17. Weathering • Types of Weathering • 1. Mechanical/Physical • 2. Chemical rocks are dissolved/chemically changed. • Salt dissolved in water • Rust

  18. Reminder • Weathering ~ rocks break apart ( fragments/dissolved ) • Factors present and affecting weathering • Water Temperature Pressure Surface area

  19. Types of Chemical Weathering • Hydrolysis chemical reaction of water with other substances. • Minerals are “dissolved”/fall apart in water. • Halite NaCl dissolves in water • water molecules break NaCl bonds

  20. Types of Chemical Weathering • OxidationReaction of Oxygen in air/water with metallic elements • O2 + metal Oxide “rust” • “Rust” is loosely formed on the surface of the original metal. Iron oxide Copper oxide

  21. Types of Chemical Weathering • Acid Precipitation • CO2 in the air + water produceCarbonic acid • Limestone is dissolved in weak acidic water.

  22. Types of Chemical Weathering • Thermal effect • Ex. Salt dissolves faster in hot water than in cold water. • thehigher temperature of air and water • the more intense rate of chemical weathering

  23. Review • Explain how water dissolves minerals. • Hydrolysis • What condition(s) can intensify this process? • Higher Temperature • More water • More surface area • Explain how a limestone statue is chemically weathered. • Calcite ~ Ca CO3 • Carbonic Acid

  24. Review • Describe what is happening to the Statue of Liberty? • Oxidation • Cu +O2Copper Oxide • What will eventually happen to a chemically weathered object? • Its original material is dissolved/chemically changed. • Falls apart/Disappears!

  25. Chemical Weathering Lab • Lab

  26. Weathering Review • Explain the difference between mechanical and chemical weathering. • Mechanical ~ rocks break into smaller pieces. • Chemical ~ rocks dissolve/chemically change. • Describe possible weathering processes that are occurring in this picture.

  27. Weathering Review • Mechanical and Chemical weathering may occur at the same time/place.

  28. Weathering • Biological Weathering • Lichens: colonies of fungi and algae • Mechanical ~ microscopic roots • Chemical ~ molecular breakdown of minerals • “Eat away” at the surface of the rock • Leave loose, unused rock/mineral material

  29. Lichens Lichens are actually two types of organisms, microscopic fungi and algae, working symbiotically, or together. The fungus keeps the algae moist, and the algae makes food for both organisms. This partnership allows lichens to live in some of the most inhospitable places on Earth, such as barren rock. The many types of lichen range in color from the palest green to bright orange to black. Most of the lichens normally seen are epilithic, meaning they reside on the surface of the rock. The endolithic lichens make their way into rock, while chasmolithic lichens can survive in cracks within rockRead more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETKc8orO • Physical Weathering • With microscopic rootlike filaments, lichens can physically weather rocks. Parts of lichens called hyphae and rhizines find their way between the grains of rock. Once there, the lichens' repeated swelling and shrinking increases the size of the gaps, allowing more lichens to enter and continue the process. Eventually, the rock forms cracks along its surface and/or sheds part of its top layer.Read more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETKjZxDF • Chemical Weathering • Lichens make chemicals that react with other substances to eat away at rock slowly. One of the biggest weathering agents is oxalic acid, which occurs naturally in lichens. When oxalic acid reacts with the environment, it leaches calcium carbonate from rocks and replaces it with a weaker substance.Read more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETKxbSZC • Lichens help to erode rocks in other ways. Water from the sky and carbon dioxide from the lichens mix with a common rock compound called calcium bicarbonate to form calcium carbonate, a liquid that is easily washed away by rain. In the same way, lichens can help turn rock-hard magnesium bicarbonate into the highly erodible magnesium bicarbonate.Read more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETLQhKBw • Effects • In some cases, lichen growing inside a rock can weather the rock 200 to 300 times faster than geological processes such as wind and water. During decades and centuries, lichens can turn barren boulders into chunks of rock with deep fissures and a layer of organic matter. This allows small plants such as mosses to gain a foothold. These plants further weather rock so soil and, eventually, a new ecosystem can form. • Lichens can bring unwanted weathering to statues, tombstones, stone buildings and other elements that humans would rather remain intact and unvarnished.Read more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETLdJ4W5 • Effects • In some cases, lichen growing inside a rock can weather the rock 200 to 300 times faster than geological processes such as wind and water. During decades and centuries, lichens can turn barren boulders into chunks of rock with deep fissures and a layer of organic matter. This allows small plants such as mosses to gain a foothold. These plants further weather rock so soil and, eventually, a new ecosystem can form. • Lichens can bring unwanted weathering to statues, tombstones, stone buildings and other elements that humans would rather remain intact and unvarnished. Read more: What Are Biological Weathering Lichens? | eHow.comhttp://www.ehow.com/info_8551957_biological-weathering-lichens.html#ixzz2ETLdJ4W5

  30. Do Now Question • How does your garden grow? • Name and describe conditions needed for a plant to grow. • * • * • * • * • * • * • Sun • Water • Nutrients • air • Soil

  31. Soil

  32. Soil • Regolith Sediments on earth’s surface • Humus Decomposed organic matter ( nutrients ) • Mixture of Regolith, Humus, water, & air • Soil Supports plant life

  33. Soil • Soil formation YOUNG MATURE

  34. Soil Horizons • Mature soils have develop distinct layers/Horizons • Texture: Sediment grain size • Composition: Organic matter • Organic Horizon: 100% Humus layer • A Horizon: Top Soil • Sediment Layer (coarse-grain) ) • 25% Humus • B Horizon: Subsoil/Zone of Accumulation • Fine-grained • 5% Humus Impermeable Clay layer _____________ • C Horizon: Weathered bedrock surface • Unsorted texture • No Humus • Bedrock: Original Parent Rock Layer

  35. Soils Review • Explain how each soil horizon is described. • Texture & Composition • Which soil Horizon has the most amount of plant root activity? • A Horizon, Top Soil • Explain why O Horizon is not as good as the A Horizon for plant roots? • No regolith pore space for air and water • Where is the Clay layer? • At the bottom of the B Horizon • Which soil Horizon has the least amount of plant root activity? • C Horizon • Explain why. • No Humus in C horizon due to the clay layer • Describe the texture of the C Horizon. • Unsorted sediments of the weathered surface of bedrock

  36. Soil Profiles • Soil Profiles

  37. Soil • Types of climates

  38. Soil Types • Soils are affected by climate regions. • Temperature, water, & organic activity • 1. Polar Water permanent freeze • Soil permafrost • A Horizon thin & low% humus • 2. Desert Water arid/not much • A Horizon thin & low% humus • 3. Tropical Water plenty/too much • A Horizon thin & low% humus • 4. Temperate Water plenty/enough • A Horizon thick & high% humus • Forest, *Prairie ( grass land ) • * Agriculture

  39. Comparing Soil Types Lab

  40. Types of Soils & Climates

  41. Soils Lab • MiniLab p 172 Qs. 1-3 • SGCM Critical Thinking p. 40

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