Ch.6 – Sedimentary and Metamorphic Rocks

Formation of Sedimentary Rocks Sedimentary Rock Formation Weathering Erosion Deposition Weathering & Erosion 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