Sedimentary rocks
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Sedimentary rocks

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Sedimentary rocks Sedimentary rocks Presentation Transcript

  •  
  • - 75% of the rocks exposed at the surface are sedimentary rocks.
  • - sediments are loose materials such as rock fragments, mineral grains, and bits of plant and animal remains that are moved by wind, water, ice, or gravity.
  • - sedimentary rock forms when sediments are pressed and cemented together, or when minerals form from solutions.
  •  
  • - sedimentary rocks often form in layers
  • - older rocks are usually found at the bottom layers, however, sometimes forces within Earth overturn layers of rock, and the oldest are no longer at the bottom.
  •  
  • - sedimentary rocks are usually classified as detrital, chemical or organic.
    • detrital = clastic
    • chemical and organic = nonclastic
    • * you need to know all of these terms!!!
  • - Detrital sedimentary rocks: made from broken fragments of other rocks
  • 1. when rock is exposed to air, water, or ice, it is unstable and breaks down. This process, which breaks rocks into smaller pieces, is called weathering.
  • 2. when layers of small sediments stick together because of pressure, compaction occurs.
  • 3. when water and other minerals (such as quartz, calcite and hematite, which act as naturally glues) move through open spaces between larger sediments, gluing them together, cementation occurs.
  • 4. Detrital rocks have granular textures, much like granulated sugar. They are named according to the shapes and sizes of the sediments that form them. Breccia: angular Conglomerate: rounded
    • Big Sediments Conglomerate (round pebbles)
      • boulders
      • pebble
      • gravel
      • sand sandstone (feels sandy, has pores)
      • silt shale (feels smooth, pressure from layers)
      • clay
      • Small Sediments
  • Chemical sedimentary rocks: form when dissolved minerals come out of solution.
    • - chemical sedimentary rocks are different: they are not made from pieces of preexisting rock.
  • - limestone: when calcium carbonate comes out of solution in the form of calcite
  • - limestone is usually deposited on the bottom of lakes or shallow seas.
  • - large areas of the central U.S. have limestone bedrock because seas covered much of the country for millions of years.
  • - The mineral halite forms rock salt when water that is rich in dissolved salt evaporates.
  • Michigan Basin
  • - companies mine deposits of rock salt as an important resource.
  • - Organic Sedimentary Rocks: made from remains of once-living plants or animals.
  • - fossil-rich limestone: similar to chemical limestone (both made of calcite) however, fossil-rich limestone mostly contains remains of once-living ocean organisms instead of only calcite.
  •  
  • - chalk is made of microscopic shells.
  • - coal is made of plant remains, chemically changed by microorganisms compacted over millions of years.
  • - The rock cycle is a continuous and dynamic process.