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Weathering: Mechanical or Chemical?

Weathering: Mechanical or Chemical?. (Take notes as we go through the slide show.). What is Mechanical Weathering?. The process that breaks rocks into different shapes and smaller pieces. (Changes the rock’s physical appearance).

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Weathering: Mechanical or Chemical?

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  1. Weathering:Mechanical or Chemical? (Take notes as we go through the slide show.)

  2. What is Mechanical Weathering? The process that breaks rocks into different shapes and smaller pieces. (Changes the rock’s physical appearance)

  3. TEMPERATUREHeating & cooling cause rocks to expand and contract. Temperature changes cause outer layers of rock to crack .Exfoliating is when the outer layers of rock crack and break off .

  4. Changes in Temperature cause Exfoliation Mechanical (Physical)

  5. Temperature: Exfoliating Rock

  6. FROST ACTIONLiquid water seeps into cracks and expands when frozen causing small cracks to widen and open up

  7. Frost Action: Freezing and Melting of Water (Ice Wedging) Mechanical (Physical)

  8. Frost ActionIce Wedge

  9. Frost Action

  10. ORGANIC ACTIVITYAnimals scratch and dig on the surface breaking rocksPlant roots break up soil, even asphalt and concrete

  11. Organic Activity: Animals Breaking Down Rocks Mechanical (Physical)

  12. Animal Activity

  13. Organic Activity: Tree Roots Cracking Cement (Root-Pry) Mechanical (Physical)

  14. Organic Activity: Root Pry

  15. GRAVITY • Gravity can pull loosened rocks down hills or mountains in a landslide, when mixed with water, it is a mudslide

  16. Gravity:Landslide Mechanical (Physical)

  17. ABRASION • Wind carrying particles smooth rocks on the surface • Water carrying particles smooth rocks in rivers/oceans

  18. Abrasion: Wind & Sand Mechanical (Physical)

  19. Abrasion: Wind & Sand

  20. What is Chemical Weathering? The process that changes the mineral composition or chemical makeup of the rocks. Minerals can be added or removed from rocks. OR Minerals in the rocks can be broken down.

  21. WATER • Water can dissolve most types of minerals that hold rocks together – these rocks are said to be soluble which means able to dissolve

  22. Water & Oxidation Chemical

  23. OXIDATION • Oxygen chemically combines with other elements such as Iron making iron oxide or rust (orange/brownish new material)

  24. Oxidation: Rust Chemical

  25. Oxidized Copper

  26. CARBONATION • When carbon dioxide dissolves into water it is called carbonic acid – think about a carbonated beverage like soda – this can dissolve rocks but is too weak to harm people or plants. It can dissolve limestone or soft rocks

  27. Water & Acids:Cave Formation

  28. Limestone Caves Chemical

  29. SULFURIC ACID • Sulfur dioxide is a byproduct of burning fossil fuels and it combines with water too to form acid rain • Acid rain affects marble statues, paint, and metal

  30. Acid Rain Chemical

  31. Acid Rain Chemical

  32. PLANT ACIDS • Plants produce weak acids that break down rocks – lichens or mosses break down rocks and can form soil • Also, some plants such as cactus produce acids to prevent other plants from growing too close to them

  33. Plant Acid: Lichen Creates an Acid Chemical

  34. Lichen covered Rocks

  35. What Factors Affect the Rate of Weathering? • COMPOSITION of the rock – what the rock is made up of 2. CLIMATE where rock is found 3. Amount of TIME rock is exposed to the Earth’s surface 4. Amount of EXPOSED SURFACE AREA – smaller pieces allow for more rock surfaces to be exposed

  36. What Types of Weathering?

  37. What type of weathering?

  38. What type of weathering?

  39. What type of weathering?

  40. What Type of weathering?

  41. Mechanical vs. Chemical Mechanical: GO FAT Chemical: COWS P Carbonation Oxidation Water Sulfuric Acid Plant Acids • Gravity • Organic Activity • Frost Action • Abrasion (wind) • Temperature

  42. A weathered face….ahhhhh!!

  43. ROCKS • Hard solids made from one or more minerals. • IGNEOUS • SEDIMENTARY • METAMORPHIC

  44. Rock Exterior……vs…..

  45. ….Rock Interior

  46. MINERALS • Natural, non-living solid with a chemical composition (elements from the periodic table) and a crystal structure • Have Differences in : • Color Crystal Shape • Luster (reflecting light) Fracture • Density Streak

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