Formation Of Sedimentary Rocks PDF

24/10/20 Chapter 6 Section 1 & 2 How are sedimentary rocks formed? 1  24/10/20 How can the different types of cl...

24/10/20 Chapter 6 Section 1 & 2 How are sedimentary rocks formed? 1  24/10/20 How can the different types of clastic sedimentary rocks be described? Weathering and Erosion Sediments are small pieces of rock that are moved and deposited by water, wind, glaciers, and gravity. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 2  24/10/20 Weathering and Erosion Weathering Chemical weathering occurs when the minerals in a rock are dissolved or otherwise chemically changed. During physical weathering, minerals remain chemically unchanged. Rock fragments break off of the solid rock along fractures or grain boundaries. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Weathering and Erosion Weathering When exposed to both chemical and physical weathering, granite eventually breaks apart and might look like this decomposed granite. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 3  24/10/20 Weathering and Erosion Erosion The removal and transport of sediment is called erosion. The four main agents of erosion are wind, moving water, gravity, and glaciers. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Weathering and Erosion Erosion After rock fragments and sediments have been weathered out of the rock, they often are transported to new locations through erosion. Eroded material is almost always carried downhill. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 4  24/10/20 Weathering and Erosion Deposition Deposition occurs when transported sediments are deposited on the ground or sink to the bottom of a body of water, forming layers with the largest grains of sediment at the bottom. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Weathering and Erosion Energy of transporting agents As moving water slows down, some sediment deposits are sorted into layers of different-sized particles. The largest particles settle out first, then the next largest, and so on. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 5  24/10/20 Weathering and Erosion Energy of transporting agents Wind can move only small grains, so sediment deposits made by wind are usually fine and well-sorted. Some sediment deposits contain particles of all sizes because they are dumped in unsorted piles when, for example, a glacier melts or there is a landslide. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Lithification As more sediment is deposited in an area, the bottom layers are subjected to increasing pressure and temperature. These conditions cause lithification, the physical and chemical processes that transform sediments into sedimentary rocks. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 6  24/10/20 Lithification Compaction Lithification begins with compaction. The weight of overlying sediments forces the sediment grains closer together, causing physical changes. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Lithification Cementation Cementation occurs when dissolved minerals precipitate out of groundwater and their growth glues sediment grains together into solid rock. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 7  24/10/20 Sedimentary Features Bedding The primary feature of sedimentary rock is horizontal layering called bedding, which results from the way sediment settles out of water or wind. Bedding in which the particle sizes become progressively heavier and coarser toward the bottom layers is called graded bedding. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Sedimentary Features Bedding Cross-bedding is formed as inclined layers of sediment are deposited across a horizontal surface. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 8  24/10/20 Sedimentary Features Ripple marks When sediment is moved into small ridges by wind or wave action or by a river current, ripple marks form. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Visualizing Cross-Bedding and Ripple Marks Moving water and loose sediment result in the formation of sedimentary structures such as cross-bedding and ripple marks. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 9  24/10/20 Sedimentary Features Evidence of past life Fossils are the preserved remains, impressions, or any other evidence of once-living organisms. During lithification, parts of an organism can be replaced by minerals and turned into rock, such as shells that have been mineralized. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks Sedimentary Features Angular vs. rounded As sediment is transported, pieces that began with an angular shape knock into each other and become rounded as their edges are broken off. Copyright © McGraw-Hill Education Formation of Sedimentary Rocks 10  24/10/20 Clastic Sedimentary Rocks The most common sedimentary rocks, clastic sedimentary rocks, are formed from the abundant deposits of loose sediments that accumulate on Earth’s surface. Clastic refers to rock and mineral fragments produced by weathering and erosion. These rocks are further classified according to the sizes of their particles. Copyright © McGraw-Hill Education Types of Sedimentary Rocks Clastic Sedimentary Rocks Coarse-grained rocks Sedimentary rocks consisting of gravel-sized rock and mineral fragments are classified as coarse-grained rocks. Copyright © McGraw-Hill Education Types of Sedimentary Rocks 11  24/10/20 Clastic Sedimentary Rocks Coarse-grained rocks Conglomerates have rounded, gravel-sized particles. Breccias are composed of angular, gravel-sized particles. Copyright © McGraw-Hill Education Types of Sedimentary Rocks Clastic Sedimentary Rocks Medium-grained rocks Sedimentary rocks that contain sand-sized rock and mineral fragments are classified as medium-grained clastic rocks. Porosity is the percentage of open spaces between grains in a material, such as rock. Copyright © McGraw-Hill Education Types of Sedimentary Rocks 12  24/10/20 Clastic Sedimentary Rocks Medium-grained rocks When open spaces between grains in a rock are connected to one another, fluids can move through porous rock such as sandstone. Sandstone layers can be valuable as underground reservoirs of oil, natural gas, and groundwater. Copyright © McGraw-Hill Education Types of Sedimentary Rocks Clastic Sedimentary Rocks Fine-grained rocks Sedimentary rocks consisting of silt- and clay-sized particles are called fine- grained rocks. Fine-grained sedimentary rock has low porosity and often forms barriers that hinder the movement of groundwater and oil. Copyright © McGraw-Hill Education Types of Sedimentary Rocks 13  24/10/20 Chemical and Biochemical Sedimentary Rocks Chemical sedimentary rocks When the concentration of dissolved minerals in a body of water reaches saturation, crystals can precipitate out of solution and settle to the bottom. The resulting layers of chemical sedimentary rocks are called evaporites. Copyright © McGraw-Hill Education Types of Sedimentary Rocks Chemical and Biochemical Sedimentary Rocks Chemical sedimentary rocks The constant evaporation from a body of salt water results in precipitation of large amounts of salts. Copyright © McGraw-Hill Education Types of Sedimentary Rocks 14  24/10/20 Chemical and Biochemical Sedimentary Rocks Biochemical sedimentary rocks Biochemical sedimentary rocks are formed from the remains of once-living organisms. The most abundant of this type of rock is limestone, which is composed primarily of calcite. Copyright © McGraw-Hill Education Types of Sedimentary Rocks Chemical and Biochemical Sedimentary Rocks Biochemical sedimentary rocks After the death of organisms that used calcium carbonate to make their shells, the shells settle to the bottom of the ocean and can form thick layers of carbonate sediment. During burial and lithification of the carbonate sediment formed from the shells of once-living organisms, calcium carbonate precipitates out of the water, crystallizes between the grains of carbonate sediment, and forms limestone. Copyright © McGraw-Hill Education Types of Sedimentary Rocks 15  24/10/20 Sedimentary Identify Group of three 1. Carefully observe the following characteristics of each rock: 1. Grain Size 2. Color 3. Rounded or Angular pieces 2. Design a data table to record your observations. 3. With you data answer Which group Classify Compare and contrast your samples using the data from the data table. 1. How are Sedimentary rocks different from Igneous? 2. What characteristics do each of the groups share? Speculate Which process do you think these rocks were formed compaction or cementation. Homework Read Chapter 6 Section 3 Before You Leave!! Hand ins: Nothing for today 16