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Rocks

Rocks. GEOG 3251 Mountain Geography summer term B 2010. Rock cycle. Definition & classification. Rock = a naturally occurring aggregate of minerals and/or mineraloids . Classification: mineral and chemical composition; the texture of the constituent particles

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Rocks

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  1. Rocks GEOG 3251 Mountain Geography summer term B 2010

  2. Rock cycle

  3. Definition & classification • Rock =a naturally occurring aggregate of minerals and/or mineraloids. • Classification: • mineral and chemical composition; • the texture of the constituent particles • processes that formed them.

  4. Types of rocks • igneous • sedimentary • metamorphic

  5. Igneous rocks Formed from molten magma (latin ignis = "fire") 2 types: • intrusive: magma cools and crystallises slowly within the Earth's crust • extrusive: magma reaches the surface either as lava or fragmental ejecta.

  6. Classification based on mode of occurrence

  7. Based on composition

  8. FELSIC ROCKS: texture Extrusive Intrusive Muy extrusive Granite Rhyolite Obsidian finer coarser

  9. Yosemite Valley: El Capitan Intrusive: slow cooling, large texture

  10. ARROWHEADS Obsidian Extrusive: fast cooling, fine texture

  11. Igneous Rock Types Figure 11.7

  12. Sedimentary rocks • Two ways of forming: • from overburden pressure as particles of sediment are deposited out of air, ice; • chemical precipitates (water flows carrying the particles in suspension), eg. carbonate-rich sediments

  13. What makes the Flatirons so good for climbing? Type of rock? • Sandstone • conglomerate • -large particles • -good handholds

  14. Limestone(Ca CO3) • Piatra Craiului, Carpathians (Romania) • Karst landscape

  15. Limestone caves

  16. Metamorphic rocks • formed by subjecting any rock type (including previously-formed metamorphic rock) to different temperature and pressure conditions than those in which the original rock was formed

  17. Metamorphic rocks • Foliated: stress that deforms the rock in one plane, e.g. slate is a foliated metamorphic rock, originating from shale. • Non-foliated: do not have planar patterns of stress; rocks that were subjected to uniform pressure from all

  18. SLATE Because slate easily flakes, it’s ideal for Floors, roofs, blackboards.

  19. GNEISS Gneiss is characterized by a banded or foliated pattern. Granite is a precursor rock to gneiss

  20. Stress vs.strain • Stress = force per unit area • Strain = amount of deformation an object experiences compared to its original size and shape • Compression: Longitudinal strain that shortens an object. • Tension: Longitudinal strain that lengthens an object.

  21. Behavior of Materials • Elastic • Material deforms under stress but returns to its original size and shape when the stress is released. • Plastic • Material does not flow until a threshold stress has been exceeded. • Brittle • Material deforms by fracturing. Glass is brittle. Rocks typically brittle at low temps and pressures.

  22. How do rocks behave when subjected to stress?

  23. Folding

  24. Faulting

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