Elemental Composition of the Earth’s Crust

1. Elemental Composition of the Earth’s Crust 1

2. The Rock Cycle • Igneous rocks- rocks that form directly from magma. • Intrusive igneous- form from within Earth as magma cools. • Extrusive igneous- from when magma cools above Earth. (ex. A volcano that ejects magma out will form this) • Sedimentary rocks- form when sediment such as mud, sands, or gravels are compressed by overlying sediments. • Metamorphic rocks- form when sedimentary, igneous or other metamorphic rocks are subjected to high temperatures and pressures.

4. Weathering and Erosion • Weathering- when rocks are exposed to air, water, certain chemicals or biological agents that degrade the rock. • Physical weathering- the mechanical breakdown of rocks and minerals.

5. Weathering and Erosion • Chemical weathering- the breakdown of rocks and minerals by chemical reactions.

6. Erosion • Erosion- the physical removal of rock fragments from a landscape or ecosystem. Wind, water, ice transport and living organisms can erode materials. • Deposition- the accumulation or depositing of eroded material such as sediment, rock fragments or soil.

7. Soil Components

8. Five soil forming factors • Parent material : Rocks • Climate : Precipitation, Temperature changes • Organisms : Bacterial and fungal colonies, worms, rodents • Topography : Slope, Landscape position • Time : How long climate has been altering parent material geologic time

9. An E horizon can develop in this area. Bedrock can lie below the C horizon. In this position, the bedrock is called an R horizon.

10. Texture Texture is often the first characteristic soil scientists determine. It is the relative proportion of sand, silt, & clay sized particles in the fine earth fraction of a soil horizon. The fine earth fraction is all of the individual particles that are smaller than 2mm in diameter. Everything larger than sand is excluded. . . Silt Particle 2mm sand particle magnified 133x Clay particle

12. Reserves • Reserves- the known quantity of a resource that can be economically recovered. 12

13. Categories of Mineral Resources Identified Undiscovered Reserves Economical Other resources Decreasing cost of extraction Not economical Decreasing certainty Known Existence Fig. 12-7, p. 276

14. Types of Mining • Subsurface mining- mining for resources that are 100 m below Earth’s surface. 14

15. Open-pit Mine Fig. 12-8, p. 277

16. Spoil from an Unrestored Area Strip Mine Fig. 12-9, p. 277

17. Contour Strip Mining Undisturbed Land Overburden Highwall Coal seam Overburden Pit Bench Coal seam Spoil Banks Fig. 12-10, p. 277

18. Mountaintop Mining Fig. 12-11, p. 278

19. Typical Life Cycle of a Metal Resource Surface mining Metal ore Separation of ore from gangue Smelting Melting metal Conversion to product Discarding of product(Scattered in environ-ment) Reuse Recycling Fig. 12-13, p. 279

20. Depletion Curves for a Nonrenewable Resource Mine, use, throw away; no new discoveries; rising prices A Recycle; increase reserves by improved mining technology, higher prices, and new discoveries B Production Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices, and new discoveries C Present Depletion time A Depletion time B Depletion time C Fig. 12-14, p. 280 Time