1. Chapter 2 Section 4: Sedimentary Rocks
Objectives
Explain how sedimentary rocks form sediments
Classify sedimentary rocks as detrital, chemical or organic in origin

2. Formation of Sedimentary Rocks
75% of surface rocks are sedimentary rocks
Sediments: loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice or gravity.
Sedimentary Rock
Forms when sediments are pressed and cemented together or when minerals form from solutions.

3. Stacked Rocks
Sedimentary rocks are formed with layers. Oldest layer on the bottom and the youngest is at the top

4. B. Classifying Sedimentary Rocks
Detrital
Chemical
Organic
Only rocks to have fossils

5. C. Detrital Sedimentary Rocks
To wear away
Made from the broken fragments of other rocks

6. Weathering and Erosion
Weathering: Exposure to and break down (chemically and mechanically)of rock by air, water or ice
Erosion: the movement of eroded sediment

7. 2. Compaction
As layers of sediment build up, pressure from upper layers on lower layers compacts lower layers into rock.

8. 3. Cementation Large sediment needs to be cemented.
Occurs when minerals are deposited between the pieces of sediments and cemented together making a detrital sedimentary rock

9. 4. Shape and Size of Sediments
Clay
Silt
Sand
Pebbles
Cobbles
Boulders

10. 5. Minerals found in Sedimentary Rocks
Conglomerate usually consists of quartz and feldspar
Concrete not a rock - does not occur in nature
Sandstone is formed from smaller particles of conglomerates and breccias

11. D. Chemical Sedimentary Rocks
Form when dissolved minerals come out of solution or when liquid evaporates

12. Limestone
Calcium carbonate is carried in solution in ocean water. When it comes out of solution as calcite and it many crystals grow together limestone forms

13. 2. Rock Salt
When sea water that is rich in salt is dissolved, it often deposits the mineral halite. Halite forms rock salt

14. E. Organic Sedimentary Rocks
Rocks made of the remains of once living things
Example - limestone

15. Chalk
Made of microscopic shells

16. 2. Coal
Forms from compacted plant remains