Transcript Chapter 6 Notes

Earth & Space Science
Chapter 6
Sedimentary and Metamorphic Rocks
Weathering vs. Erosion
Weathering:
• produces sediment by breaking down rock
• can be chemical or mechanical
Erosion:
• transports sediment through
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moving water
wind
gravity
glaciers
Draw a picture of each
of these factors.
How can rocks form from sediment?
• Lithification (lithos = stone):
– Compaction—compression by overlying layers
(sometimes pore space left, esp. sandstone)
– Cementation—mineral “glue”
• Sedimentary features
– Bedding (seen in hwy rock cuts)
– Ripple marks
– Sorting/rounding of grains
– Fossils
Sedimentary Rock Features
Bedding (horizontal layering):
Sedimentary Rock Features
• Most fossils are found in sedimentary rocks.
Types of Sedimentary Rock
Clastic—made of small bits (clasts) stuck together
• Coarse (>2 mm pieces)
– conglomerate
• Medium (1/16 mm to 2 mm)
– sandstone
• Fine (1/256 mm to 1/16 mm)
– siltstone
• Very fine (< 1/256 mm)
– shale
Types of Sedimentary Rock
Organic/Biochemical formed from/by living
organisms
• Coal
• Fossiliferous limestone
• Coquina
• Chalk
Types of Sedimentary Rock
Chemical evaporites and precipitates
• Rock salt
• Rock Gypsum
• Compact limestone
• Chert/flint
What causes metamorphism?
• Temperature
• Pressure
Features of Metamorphic Rocks
• Solid state change in minerals (remember
Bowen’s reaction series?)
• Foliation—parallel layers or bands—caused by
pressure
• Reorganization of crystals
Protoliths of Foliated Rocks
• Granite  gneiss (banded)
• Various  schist (layered)
• Shale  slate (layered)
Protoliths of Nonfoliated Rocks
• Limestone  marble
• Sandstone  quartzite
Types of Metamorphism
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Low grade to high grade
Regional
Contact
Hydrothermal (hot groundwater)
Economic Importance
of Metamorphic Rocks
• Building/Construction
– Slate, marble
• Metallic mineral resources
– Ores (iron, lead)
– Native minerals (gold, copper, silver)
• Nonmetallic mineral resources
– Talc, asbestos, graphite
The Rock Cycle