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"To the dull mind all nature is leaden. To the illumined mind the whole world burns and sparkles with light." -- Ralph Waldo Emerson

See some

go to USGS

 Go to the Volcano World Sedimentary Rock Lesson...
 

Form when sediments are cemented or compacted together

• sometimes after erosion has deposited them
• sometimes after they have precipitated out of solution

Sediment
 

• Is loose material

• Rock, gravel, sand, silt, mud, even plant and animal remains
• That have been eroded by wind or water

  or

• come out of solution (precipitate) and settle to the bottom of a body of water
  • Any rock type can weather and erode to become part of a sedimentary rock

Compaction

Squeezing together, often squeezing out water, till the particles stick

• This requires much time and great pressures
• Usually only works with very small particles

Cementation

• Water moving through spaces between particles dissolves minerals that are natural cements (calcite, hematite, limonite) causing the particles to be "glued" together.

 - Larger particles, sand, gravel

Sedimentary Rock Layers

• are deposited over time
• oldest are obviously on bottom
• youngest are on top
• can be disturbed by subsequent forces from within the earth

CLASSIFICATION OF SEDIMENTARY ROCKS

Detrital

• Also known as clastic
  • Formed from detritus, the worn-away fragments of pre-existing rocks

Shape and Size

Size,Shape	Name
Large, Angular	Breccia
Large, Rounded	Conglomerate
Sand-sized	Sandstone
Clay-sized	Shale

 

Chemical

Precipitates

• Form from precipitation out of solution

- Most limestones

Evaporates

• Left behind when solutions evaporate

- Rock salt

Organics

• Fossiliferous (fossil-rich) limestone.

• Very small sizes
• Chalk
• Larger sizes
• Coquina - considered to have a clastic texture

• Coal

• Dead plant material.
• Chemical changes and Compaction over a very long time.