Earth Materials and Landforms:
Sedimentary and Metamorphic Rocks

Sedimentary Rocks

• Formed by the compaction and cementation of fragments from pre-existing rocks or plant/animal (shells) remains

Properties of sedimentary rocks

• Lithification (cementation, compaction and hardening)
• Stratification - layering

Types

• Chemically precipitated - formed from a precipitate. (example: limestone)
• Clastic - formed from rock fragments (example: sandstone)
• Biologic (organic) - formed from plant/animal remains (example: coal)

Click image to enlarge Limestone (chemically precipitated)	Click image to enlarge   Sandstone (clastic sedimentary)
Limestone, a chemically precipitated sedimentary rock shown in the photograph on the left, is formed by the compaction and lithification of the shells from marine organisms. Sandstone, on the right, is formed by the compaction of quartz grains.

Karst Landscapes

• Landscape developed from the solution of limestone bedrock; common in southern Indiana, Kentucky, Florida, China, eastern Europe
• Features:
  • Sinkholes - Sinkhole threatens home
  • Caverns
  • Disappearing and underground streams
  • Karst window

Metamorphic Rocks

Origin, Occurrence, and Properties

• Heat and pressure causes rock material to either:

• flow as a plastic material or,
• Undergo chemical recrystallization into a new material

Types

• Foliated (banded) - minerals oriented along visible planes

• Example: Schist (fine grain) (from slate)
• Example: Gneiss (coarse grain) (from a variety of rock, one of which is granite)

• Non-foliated (no banding) usually rock of one mineral)

• Example: Quartzite (from sandstone - quartz)
• Example: Marble (from limestone - calcium carbonate)

Gneiss, a foliated metamorphic rock	Marble, non-foliated metamorphic rock
Examples of foliated and non-foliated metamorphic rocks are shown above. On the left is gneiss, showing minerals aligned along visible planes typical of foliated metamorphic rocks. Gneiss can form from the metamorphism of granite. On the above right is a picture of marble, a typical non-foliated metamorphic rock. Marble is a product of the metamorphism of limestone.

To Rock cycle    

Can you ...

• Describe the basic types of sedimentary rocks? Give examples.
• Describe the difference between foliated and nonfoliated metamorphic rocks?