9-12

F5: Demonstrate how rocks and minerals are used to determine geologic history.

Organizing Questions	Describe the history of this rock. List the geologic processes involved in the formation of each rock group. Describe the agents of metamorphism. Discuss the origin of materials that accumulate as sediment. Describe the processes of weathering, erosion, and mass wasting.
Elaboration
Specific Ideas	The formation, weathering, sedimentation, and reformation of rock constitute a continuing "rock cycle" in which the total amount of material stays the same as its forms change. Benchmark 4C2 We can observe some changes such as earthquakes and volcanic eruptions on a human time scale, but many processes such such as mountain buuilding and plate movements take place over hundreds of millions of years. NSES D3C pgs. 189-190 Geologic time can be estimated by observing rock sequences and using fossils to correlate the sequences at various locations. NSES D3b p. 189
Developmental & Instructional Implications	Students, however, may show more interest in the phenomena than in the role the phenomena play in sculpting the earth. So teachers should start with students' immediate interests and work toward the science. Students may find it harder to take seriously the less-obvious, less-dramatic, long-term effects of erosion by wind and water, annual deposits of sediment, the creep of continents, and the rise of mountains. Students' recognition of those effects will depend on an improving sense of long time periods and familiarity with the effect of multiplying tiny fractions by very large numbers (in this case, slow rates by long times). Benchmarks p. 71
Examples

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