Post on 18-Jan-2016
Earth & Space ScienceChapter 6
Sedimentary and Metamorphic Rocks
Weathering vs. Erosion
Weathering:• produces sediment by breaking down rock• can be chemical or mechanicalErosion:• transports sediment through– moving water – wind– gravity Draw a picture of
each– glaciers 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 FeaturesBedding (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
• 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