Presentation on theme: "Formation of Sedimentary Rocks SWBAT sequence the formation of sedimentary rocks; explain the formation and classification of clastic sediments; describe."— Presentation transcript:
Formation of Sedimentary Rocks SWBAT sequence the formation of sedimentary rocks; explain the formation and classification of clastic sediments; describe features of sedimentary rocks
Sedimentary Rock Formation Sediments –Pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation How does the formation of sedimentary rocks begin? –Weathering and erosion produce sediments Weathering –The breakdown of rocks by physical or chemical means Erosion –Movement of weathered materials
Weathering What is the difference between chemical and physical weathering? –Chemical weathering occurs when the minerals in a rock dissolve –Physical weathering occurs when minerals remain unchanged. Rock fragments break off Clastic –From Greek klastos - broken –Rock and mineral fragments –Classified by size
4 main agents of erosion Wind –Blows broken particles to other locations Moving water –Large and small particles are transported by the currents Gravity –Pulls particles downward from hills and mountains Glaciers –Particles are dragged or frozen in glaciers and deposited when they melt
Erosion and Transport Deposition –When sediments are laid down on the ground or sink to the bottom of water –Large particles settle first, then second largest, and so on –Different sized particles are sorted into layers Lithification –Transformation of sediments into rocks through compaction and cementation Compaction –Overlying sediments force sediment grains closer together causing a physical change Cementation –Mineral growth cements sediment grains together into solid rock
Features of sedimentary rocks Bedding Graded bedding Cross- bedding Horizontal layering that can range from millimeters to many meters thick. The type of bedding depends on transport. Particle sizes become progressively heavier and coarser toward the bottom layers. In water heaviest particles settle first, followed by progressively finer material Formed when inclined layers of sediment move forward across a horizontal surface.
Evidence of Past Life Fossil –Preserved remains, impressions, or any other evidence of once-living orgainisms. –During lithification, parts of the organism can be replaced by minerals and turned into rock