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