Chapter 6 Sedimentary and Metamorphic Rock Weathering and Erosion Wherever rock is exposed at Earth s surface, it is continuously being broken down by weathering a set of physical and chemical processes that breaks rock into smaller pieces. 1
Weathering and Erosion Wherever rock is exposed at Earth s surface, it is continuously being broken down by weathering a set of physical and chemical processes that breaks rock into smaller pieces. Weathering and Erosion Sediments are small pieces of rock that are moved and deposited by water, wind, glaciers, and gravity. 2
Weathering and Erosion The formation of sedimentary rocks begins when weathering and erosion produce sediments. Chemical Weathering Chemical weathering occurs when the minerals in a rock are dissolved or chemically changed. Acid Rain 3
Physical Weathering Physical weathering occurs when rock fragments break off of solid rock along fractures. Erosion The removal and transport of sediment is called erosion. The four main agents of erosion are: wind, moving water, gravity, and glaciers. 4
Deposition When transported sediments are deposited on the ground or sink to the bottom of a body of water, deposition occurs. This forms layers of sediment with the largest grains at the bottom. This feature of layering in sedimentary rock is called bedding. 5
Graded Bedding Lithification ( to turn to stone) Lithification is the physical and chemical process that transforms sediment into sedimentary rock. Lithification begins with compaction and is completed by cementation. 6
Bedding Sedimentary rocks have features that help geologists interpret how they formed. The primary feature of sedimentary rocks is horizontal layering called bedding. 7
Graded Bedding Bedding in which the particle sizes increases toward the bottom layers is called graded bedding. Graded bedding is observed in marine sedimentary rocks that were deposited by underwater landslides. Graded Bedding 8
Cross-Bedding Cross-bedding is formed as layers of sediment are deposited across a horizontal surface. Cross-bedding is usually formed by migrating sand dunes. (Wind erosion) Cross-Bedding 9
Chapter 6.2 Types of Sedimentary Rock Describe the types of clastic sedimentary rocks Explain how chemical sedimentary rocks form Describe biochemical sedimentary rocks 10
Clastic Sedimentary Rock Clastic sedimentary rocks are the most common type of sedimentary rock, and are formed from the deposits of loose sediments on the Earth s surface. Clastic Sedimentary Rock Clastic comes from the Greek work klastos which means broken. A clast is a broken fragment of a rock = sediment 11
Clastic Sedimentary Rock 12
Coarse-grained Rocks Sedimentary rocks consisting of gravel sized rock and mineral fragments are classified as coarsegrained clastic rocks 13
Coarse-grained Rocks Forms during high velocity water flows, such as mountain streams, flooding rivers, ocean waves, and glacier meltwater. Coarse-grained Rocks Conglomerate Breccia 14
Medium-grained Rocks Sedimentary rocks that contain sand-sized rock and mineral fragments are classified as mediumgrained clastic rock Medium-grained Rocks These rocks have a high porosity (open space between grains of sediment) Oil, natural gas, and groundwater, can be found in the pore spaces of sandstone. 15
Medium-grained Rocks Sandstone Cross-bedding (wind) Ripple marks (water) Fine-grained Rocks Sedimentary rock consisting of silt and clay sized particles are called fine-grained clastic rocks. Forms in swamp and pond environments. 16
Fine-grained Rocks Siltstone Shale Burgess Shale Fossil (Trilobite) 17
Chemical Sedimentary Rock When dissolved minerals in water reach saturation, crystal grains precipitate out of solution and settle to the bottom. Layers of chemical sedimentary rock form, which are called evaporites. Evaporite Formation 18
Chemical Sedimentary Rock Rock Salt Biochemical Sedimentary Rock (organic rock) Biochemical sedimentary rocks are formed from the remains of once-living organisms. Contain shells, skeletal remains, or decomposed organic matter. 19
Biochemical Sedimentary Rock Limestone Coal Section 6.3: Metamorphic Rock Compare the different types and causes of metamorphism. Distinguish among metamorphic textures Apply the Rock Cycle 20
Recognizing Metamorphic Rock Metamorphic rocks form when pre-existing rocks are exposed to increases in temperature and pressure. Metamorphosis: To change form. 21
Recognizing Metamorphic Rock When temperature or pressure becomes high enough and rocks do not quite melt, they change form. Recognizing Metamorphic Rock Temperature and pressure can change the texture, mineral composition, or chemical composition of a rock without melting it. 22
Recognizing Metamorphic Rock The high pressures required for metamorphism come from deep burial or from compression during mountain building. Metamorphic Textures Foliated metamorphic rocks are characterized by layers and bands of minerals. High Pressure causes minerals to flatten out perpendicular to the pressure 23
Metamorphic Textures Foliated 24
Metamorphic Textures Nonfoliated metamorphic rocks are characterized by minerals that form blocky crystal shapes. Nonfoliated metamorphic rocks are not banded. Nonfoliated 25
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