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Rocks

Explore the rock cycle and learn about the classification of rocks into igneous, sedimentary, and metamorphic types based on composition, texture, and formation processes. Discover the characteristics of each rock type and their behavior when subjected to stress.

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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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