Unit 3: Rocks, Soil, & Minerals

1. Unit 3: Rocks, Soil, & Minerals

2. Weathering • Weathering • the process that breaks down rock & other substances @ Earth’s surface. • Heat, cold, water, ice, oxygen, and carbon dioxide contribute to weathering.

3. Forces • Forces of weathering break rocks into smaller pieces • Forces of erosion carry these pieces away.

4. Erosion • Erosion • the movement of rock particles by wind, water, ice, or gravity. • Weathering and erosion work together to wear down and carry away rocks at Earth’s surface.

5. Concept Check • What is the difference between weathering and erosion?

6. 2 Types of Weathering • Mechanical Weathering • Rocks are physically broken down into smaller pieces. • Occurs slowly over time, but can wear away a whole mountain. • Chemical weathering • Breaks down rock through chemical changes. • Agents include: water, oxygen, carbon dioxide, living organisms, and acid rain.

7. Forces of Mechanical Weathering • Release of Pressure • As mass is removed, pressure is reduced and the outside layer of rock flakes away. • Freezing and Thawing • Deals with temperature changes • Abrasion • The grinding away of rock particles carried by water, ice, wind, or gravity. • Plant growth • Roots of plants enter cracks in rocks and causes the rock to pry apart. • Animal actions • When animals burrow into the ground it loosens up soil and breaks apart rock.

8. Agents of Chemical Weathering • Water • Most important • Dissolves rock • Oxygen • Oxidation • E.g.: iron  rust • Carbon dioxide • Forms carbonic acid when mixed with rain water on the ground • Living organisms • Produce acids that chemically weather rock • Acid rain • When the burning of fuels produces pollutants, these harsh gases combine with rain and form acids which weather very quickly.

9. Mechanical & Chemical Together • Mechanical and chemical weathering often work together • Mechanical breaks rocks down, exposing more of the rock or mineral to chemical weathering. • Rate of weathering is determined by: • Type of rock • More permeable weathers faster • Temperature (*remember the vinegar & chalk) • High temps & high precipitation level = faster weathering

10. As the surface area of this rock is increased by mechanical weathering, it is more exposed to agents of chemical weathering

11. Climate • Both types of weathering occur faster in hot, wet climates. • Rainfall provides the water needed for chemical changes as well as freezing and thawing. • Chemical reactions occur faster at higher temperatures.

12. Examples of the Effects of Weathering • Look at the following examples of weathering. Which type of weathering do you think occurred? Why do you think that?

13. Example #1

14. Example #2

15. Example #3

16. Example #4

17. Example #5

18. Example #6

19. Example #7

20. Example #8

21. Example #9

22. Now you come up with your own example…

23. Soil • Soil is the loose, weathered material on Earth’s surface in which plants can grow. • It forms as a rock is broken down by weathering and mixes with other materials on the surface.

24. Soil Composition • Soil • mixture of rock particles, minerals, decayed organic material, air, and water. • Type of rock particles and minerals in any given soil depend on: • The rock weathering • Type of weathering that took place

25. Soil Texture • Depends on the size of individual soil particles • E.g.: sand vs. clay • Particles are classified by size • Gravel: largest (2mm and above) • Sand • Silt • Clay: smallest

26. Checkpoint • Looking back at the particle size of different types of soil, why do certain types have the texture (feel) they do? Give an example.

27. Soil Texture • Important for plant growth. • Clay is dense and heavy and typically holds a lot of water. • Sand is coarse and water drains quickly. • Loam is a type of soil that is an equal mix of sand, clay, and silt. • Best for growing plants

28. Soil Horizons • 3 horizons: • Topsoil – mix of humus, clay, & other materials. • Subsoil – mix of clay and little humus • Bedrock – partly weathered rock

29. Life in Soil • Organisms mix the soil and make spaces in it for air and water. Other soil organisms make humus, the material that makes soil fertile.

30. Soil Activity http://School.discoveryeducation.com/schooladventures/soil

31. Soil Observations • Explain your soil’s: • Color • Texture • Particle size (what do you think it has the most of – look back at your notes) • Original location • Original depth (remember the horizons) • What type of plant would grow the best in it

32. Importance of Soil • Soil is one of Earth’s most valuable resources because everything that lives on land depends directly or indirectly on soil. • Plants • Animals • Humans

33. Importance of Soil • Long time to form • Limited supply of fertile soil • Designates where farming can take place

34. Soil Damage and Loss • Can be lost to erosion by water and wind. • Water: where soil isn’t protected by a plant cover. • Wind: occurs in dry climates (e.g. dust bowl)

35. The Dust Bowl • Plowing removed the grass from the Great Plains and exposed the soil. • In times of drought, the topsoil quickly dried out, turned to dust, and blew away.

37. Soil Conservation • The management of soil to prevent its destruction • 2 methods: • Contour plowing – plowing along the curves of a slope • Conservation plowing – old crops and dead weeds are left in the crop • Also, limiting herd grazing

38. Diamond Formation • At depths of 120+ kilometers • Under great pressure and heat • This caused carbon atoms to change into diamonds • Originated from a volcanic pipe

39. 3 Main Ways Minerals Form • As hot magma cools inside the crust or as lava hardens on the surface • When the elements of a mineral dissolve in hot water (forms a solution) • When solutions evaporate

40. Processes of Mineral Formation • Minerals have been forming since the beginning of Earth • Minerals can form in 2 ways: • Through crystallization of materials dissolved in water • Through crystallization of melted materials

41. Uses of Minerals • Minerals are the source of metals, gemstones, and other materials used to make many products. • Ore • A rock that contains a metal or economically useful mineral • E.g.: Copper comes from the ore chalcopyrite