Ch 6 Sedimentary and Metamorphic Rocks Formation of

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