Sedimentation

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Sedimentation
Rocks settling down for a new home
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Sedimentation process

• Sediment can come in three sizes
• Pebbles
• Sand
• Clay

Sediment is broken off bits of rock.
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Deposition
At first a sediment is deposited. On these slides
you can see deposited pebbles. As more sediments
build up, the weight squashes the ones underneath
and puts them under pressure. This is called
compaction.
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Continuing the process
As the water is squeezed out of the spaces
between sediments, minerals that were dissolved
in the water are left behind. The residue of
evaporated minerals act like glue and stick the
sediment together. This is called cementation.
This whole process may take millions of years.
The rocks formed by this process are called
sedimentary rocks.
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Some sedimentary rocks
Sandtone Petra, Jordan
Oil Shale, Canada
Conglomerate
limestone
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What do sedimentary rocks look like?

• Some clues to sedimentary rocks
• Have grains, not crystals
• Held together by natural cement
• Are sometimes porous
• Often contain fossils

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Review

• What do we call rocks that are formed from
  sediments?
• How would you identify this type of rock?
• Name three different rocks formed from sediments

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The best place to observe layers of sedimentary
rock
Bryce Canyon Utah
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