1. Sedimentary Rocks
Section 3.3

2. Formation of Sedimentary Rocks
Sedimentary comes from the Latin word sedimentum, which means settling
All sedimentary rocks begin to form when existing rocks are broken down into sediments
There are several major processes that contribute to the formation of sedimentary rocks:
Weathering, Erosion and Deposition
Compaction and Cementation

3. Formation of Sedimentary Rocks
Weathering is the breaking down of rock into sediments
Erosion involves weathering and the transportation of sediments
Deposition is the process when water, wind, ice or gravity loses energy causing sediments to drop
Larger sediments are deposited first, smaller sediments are dropped later

4. Formation of Sedimentary Rocks
Compaction is a process that squeezes, or compacts, sediments, pushing water out
Compaction is caused by the weight of sediments
Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments

5. Classification of Sedimentary Rocks
Sedimentary Rocks can be classified into two main groups according to the way they form
Clastic – rocks that are made of weathered bits of rocks and minerals
Classified by particle size
Chemical – forms when dissolved minerals precipitate from water solutions
Biochemical sedimentary rocks contain shells and skeletal remains of organisms

6. Clastic Sedimentary Rocks
Breccia
Conglomerate
Clastic Sedimentary Rocks
Sandstone

7. Chemical Sedimentary Rocks
Chert
Rock Salt
Flint
Limestone

8. Biochemical Sedimentary Rocks

9. Features of some Sedimentary Rocks
Sedimentary rocks give clues to how, when and where the rocks formed
Layers of sedimentary rock records a period of sediment deposition. The oldest layers are found at the bottom
Ripple marks may indicate that the rock was formed along a beach or stream bed
Mud cracks are formed when wet mud or clay dried and shrank, leaving a record of a dry environment
Fossils found in sedimentary rocks can help answer questions about the rock

10. Mud cracks
Fossils
Layers of sedimentary rock
Ripple marks

11. Summary of Sedimentary Rocks
Sedimentary rocks form as the result of five major process
Weathering produces particles called sediments
Wind, water, ice and gravity erode and deposit sediments
Sediments are compacted and cemented to form sedimentary rocks
Sedimentary rocks can be classified according to how they form, by using rock formation, texture and composition

12. (Table 2 on page 79)