Chapter 6 Sedimentary Rocks

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Chapter 6Sedimentary Rocks

• Miss Holl
• Rowland High School
• October 9, 2006

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Outline

• Formation of Sedimentary Rocks
• (Chapter 6, section 1)
• Types of Sedimentary Rocks
• (Chapter 6, section 2)
• See Chapter 6 Study Guide on page 143

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Steps to form a sedimentary rock

• Weathering and erosion create sediments
• Sediments are deposited
• Sediments are buried
• Sediments are lithified into rock by the
  processes of compaction and cementation

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Weathering Erosion

• Weathering is the chemical or mechanical process
  that breaks down and changes rocks.
• Weathering rate depends on factors such as
  precipitation and temperature.
• Erosion is the movement of weathered materials
  from one location to another by agents such as
  water, wind, glaciers, and gravity.

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Sediments

• Clastic sediments are rock and mineral fragments
  produced by weathering and erosion.

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Lithification

• Sediments are lithified into rock by the
  processes of compaction and cementation.

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Features of Sedimentary Rocks

• Depositional features
• Horizontal bedding
• Cross-bedding
• Ripple marks
• Fossils
• The remains of once-living things preserved in
  sedimentary rocks

IF YOU SEE FOSSILS THE ROCK IS PROBABLY
SEDIMENTARY!!
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Three types of Sedimentary Rocks

• Clastic
• Formed from clastic sediments
• Characterized by particle size and shape
• Example conglomerate
• Chemical
• Formed by minerals precipitated from water
• Example halite
• Organic
• Formed from the remains of once-living things
• Example limestone

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The Big Picture

• Sedimentary rocks provide geologists with clues
  about what the Earths surface looked like in the
  past.
• For example, if you see RIPPLE MARKS in a
  sedimentary rock, what used to be at that
  location?
• Answer Water!

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Quiz Question

• Even though igneous rocks are the most abundant
  rocks in the Earths crust, why do you think
  those are not the kind of rocks we see most of
  the time on the ground?
• Answer The igneous rocks have been weathered and
  eroded into sediments and sedimentary rocks.