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Forming of Sedimentary Rocks

Forming of Sedimentary Rocks. Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation When these sediments become cemented together, they form sedimentary rocks. So how are sedimentary rocks formed?.

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Forming of Sedimentary Rocks

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  1. Forming of Sedimentary Rocks • Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation • When these sediments become cemented together, they form sedimentary rocks

  2. So how are sedimentary rocks formed? • Formation of sedimentary rocks begins when weathering and erosion produce sediments • Natures elements (wind, water, cold, heat, gravity, chemical precipitation) break rocks into tiny pieces • 5 factors – weathering, erosion and transport, deposition, lithification, and cementation

  3. Weathering • Weathering is a set of physical and chemical processes that break rock into smaller pieces • Chemical weathering occurs when minerals in a rock are dissolved or otherwise chemically changed • Weathering produces rock and mineral fragments known as clastic sediments (range from huge boulders to microscopic particles)

  4. Erosion and transport • After weathering occurs material is transported to new locations • Erosion is the removal and movement of surface materials from one location to another

  5. Wind erosion

  6. Water erosion

  7. Gravity erosion

  8. Glacier erosion

  9. Deposition • When sediments (material) are laid down on the ground or sink to the bottoms of bodies of water deposition occurs • Sediment form layer with largest particles on bottom and smallest on top (when deposited by water) • Glaciers and gravity – deposit everything at once • Wind – only moves small material

  10. Lithification • Once materials are deposited to a site (typically sediment basins) more and more layers continue to build up • This building up increases pressure and temperature on the bottom layers • Increased pressure and temperature cause lithification • Lithification is the physical and chemical processes that transform sediments into sedimentary rock • Material at the lowest depths in-counter increased temperatures that trigger cementation • Cementation occurs when mineral growth cements sediment grains together into solid rock

  11. Features of sedimentary rocks • Primary feature of sedimentary rock is horizontal layering called bedding • Bedding where particle size becomes progressively heavier and coarser towards the bottom layers is called graded bedding • Graded bedding frequently occurs from underwater landslides – largest and heaviest material settles first followed by progressively finer material • Cross-bedding occurs as inclined layers of sediment move forward across a horizontal surface

  12. Graded bedding

  13. Cross-bedding

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