Ch.6 – Sedimentary and Metamorphic Rocks

Formation of Sedimentary Rocks

• Sedimentary Rock Formation• Weathering• Erosion• Deposition

• Weathering & Erosion• Weathering

• The Rock breaks down or weathers into smaller fragments. This rock then mixes with water and other organic materials to form soil.

• Weathering can be chemical or mechanical.• Chemical – oxidation, rusting, acids.• Mechanical – Wind or water.• The outer layers of rock weather first, changes in structure form cracks. Over time these cracks

get larger, and the pieces of rock smaller.

Formation of Sedimentary Rocks

• Mechanical Weathering• Breaks rock into pieces by:• Freezing & Thawing• Heating & Cooling• Growth of Plants• Actions of Animals• Abrasion

Formation of Sedimentary Rocks

• Chemical Weathering• Breaks rock into pieces with:

• Water• Oxygen• Carbon Dioxide• Living Organisms• Acid Rain

Formation of Sedimentary Rocks

• Rate of Weathering• The two most important factors which determine the rate of weathering:

• Type of Rock• Climate

• Erosion• The removal and transportation of sediment.• Four main agents:

• Wind• Water• Gravity• Glaciers

Formation of Sedimentary Rocks

• Deposition• Transported sediment is deposited on the ground or at the bottom of a body

of water.

• Lithification• Compaction• Cementation

Formation of Sedimentary Rocks

• Sedimentary Features• Bedding – 2 types

• Graded Bedding• Cross Bedding

• Fossils

Types of Sedimentary Rocks

• THREE types of Sedimentary Rocks• Clastic• Chemical• Biochemical

• Clastic Sedimentary Rocks• Formed from loose sediments, classified by grain size.

• Coarse-grained – largest, ex: conglomerate.• Medium-grained – middle, ex: sandstone.• Fine-grained – smallest, ex: siltstone.

Types of Sedimentary Rocks

• Chemical Sedimentary Rocks• Mineral deposits form through evaporation and precipitation.• Ex: Evaporites, such as salt deposits.

• Biochemical Sedimentary Rocks• Formed from the remains of once living things.• Ex: Limestone

• Grades of Metamorphism• Figure 6.19 on pg.148

Metamorphic Rocks

• Recognizing Metamorphic Rocks• Rocks change without melting, under intense temperature and pressure.• Caused by deep burial, & mountain building.

• Metamorphic textures – 2 Groups• Foliated – form w/ bands of minerals. • Nonfoliated- Form w/ blocky crystal shapes.

Metamorphic Rocks

• Types of Metamorphism• Regional• Contact• Hydrothermal

Metamorphic Rocks

• Economic Importance – Read pg.150• Metallic Mineral Resources• Non-metallic Mineral Resources

• The Rock Cycle – Read pg.151• Draw Diagram – figure 6.23