Sedimentary Rocks

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Sedimentary Rocks
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Origin

• Comprise 75 of the Earths surface
• Formed when sediments become compacted and
  cemented together
• Usually has layers called strata

The highest layer has the least pressure. The
lowest layer has the most pressure.
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Compaction

• What does compaction mean?
• Layer upon layer of sediment builds up and the
  pressure from the upper layers pushes down on the
  lower layers.
• Only SMALL sediments will stick together to form
  rock

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Cementation

• What does it mean?
• Water soaks through soil and rock. The water
  dissolves minerals in soil and rock. The
  solution of minerals and water moves between the
  sediments. The sediments stick together when the
  minerals crystallize.
• Common with LARGE sediments

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Classification

• Sedimentary rocks are classified in 3 ways
• Clastic Sedimentary Rocks
• Chemical Sedimentary Rocks
• Organic Sedimentary Rocks

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Clastic Sedimentary Rock

• Made from broken fragments of other rocks.
• Conglomerate large/round fragments
• Breccia large/sharp fragments

Breccia Conglomerate
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Chemical Sedimentary Rock

• Formed from minerals crystallizing out of a
  solution

Halite (Rock Salt)
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Organic Sedimentary Rock

• Rocks formed from once-living (organic!) things.

Organic Limestone