1. Sedimentary Rocks

2. Land sedimentary environments Mountains – Formed on bedrock. Steep slopes allow sediment to travel far. Desert – wind picks us fine particles Glaciers – snow compacts to ice and the ice moves sediment below it. Beach – stretches of coastline where sediments has accumulated.

3. Clasts and weathering Clasts – pieces of rock 2 types of weathering Physical – breaking apart of rocks that are exposed to the environment. 4 ways Near-Surface Fracturing – Processes near the surface cause rocks to fracture

4. Physical weathering cont’d Frost and Mineral Wedging – Rocks are pried apart when water freezes Thermal Expansion – Heating during the day may cause rocks to break Biological Activity – Roots can grow into fractures

5. Making Sediment: Physical Weathering Fracturing Frost and mineral wedging Roots and other biologic activity

6. Chemical Weathering Minerals are broken down causing new minerals to form. 4 processes –Dissolution – some minerals are dissolved in water –Oxidation – some minerals react with oxygen to form oxide minerals

7. Chemical Weathering Hydrolysis – Silicate minerals react with water, the hydrogen ions in the water react with the minerals Biological reactions – decaying plants produce acids, some bacteria consume rocks.

8. Making Sediment: Chemical Weathering Oxidation Hydrolysis Biological reactions

9. What are the characteristics of Clastic Sediments? Clastic sediments are classified in 3 ways: Size of clasts –Boulders, cobbles and pebbles –Sand –Fine particles

10. 07.04.a Moderately sorted Poorly sorted Well sorted Observe the range of clast size (sorting) in each photograph

11. Characteristics of Clastic Sediment cont’d Shape of Clasts –Angular, rounded, partially rounded Amount of Sorting –Size and range of clasts –Poorly to well sorted (poorly has wide range)

12. 07.04.a Observe the shape of these clasts Rounded Angular Partially rounded

13. 07.04.b Controls on Size, Shape, and Sorting Steepness of slope Farther from source means rounder and smaller Strength of current Agent of transport

14. Sedimentary Rock Formation Clastic Sedimentary rocks form 2 ways Compaction- increased pressure from being buried beneath sediment forces clasts together. –Compaction forces out excess water, sediments lose up to 40% of their volume.

15. Formation of Sedimentary Rocks Cementation- after sediment is compacted open pores between sediment collects water containing dissolved minerals. –As water evaporates minerals left behind act as a cement holding the clasts together.

16. 07.05.a How Clastic Sediment Becomes Rock Compaction of clay particles Compaction of sand grains Cementation

17. Types of Cement Rocks are held together by 3 types of “cement” Calcite- CaCO 3 –Moderate hold Silica- SiO 2 –Strong hold Iron-oxide Minerals- ex. hematite –Come out of water and give mineral a reddish-color

18. 07.05.b Common Clastic Sedimentary Rocks BrecciaConglomerate SandstoneShale

19. Nonclastic Rocks Form when chemicals dissolved in water, precipitate. (when water evaporates) Also, can be biochemical –Extracted by an organism and reformed into a sedimentary rock

20. 07.06.a Rocks Formed by Chemical Reactions Rock Salt Setting Setting Travertine (limestone)

21. 07.06.a Rocks Formed by Organisms Limestone with fossils Setting SettingCoal

22. 07.06.b Other Nonclastic Sedimentary Rocks ChalkGypsum Dolostone Chert

23. Difference between Clastic and Nonclastic Clastic rocks are made up of rocks and minerals Nonclastic rocks are made by dissolved minerals left behind by evaporated water.

24. Why do sedimentary rocks have layers? Most sediment is deposited in layers. Classified by thickness and definition of layers. –Thinner, smaller layers referred to as beds.

25. How layers form Discrete event – a one-time occurrence. Ex. Flood. Change in current – Caused by change in strength or direction of current that deposited the sediment. Sediment Supply – Change in type or amount of sediment being supplied.

26. How layers form Sea-level change – global rise or fall in sea level causes sedimentary environments to move. Climate Change – Boundaries between layers reflect regional or global changes in climate.

27. Types of Beds Graded Beds- form when a current loses velocity and drops sediment. Larger sediment falls first followed by finer sediment.

28. Types of Beds Cross Beds- form when sediment moves over a dune or underwater ripple. At an angle to other beds.

29. Types of Beds Parallel Beds- form when one layer piling on another layer. Most common type.

30. Resources in Sedimentary Rocks Groundwater – moves between pores in rocks Petroleum – formed by organic- rich sedimentary rocks Coal – consolidation of plant remains in wetland environments

31. Resources in Sedimentary Rocks Cement from limestone – produced from limestone free of impurities Salt – mined from ancient sedimentary salt layers Uranium – Occur in sandstone and other sedimentary rocks but it is not formed there…brought by groundwater

32. 07.14.a Resources in Sedimentary Rocks GroundwaterPetroleumCoal Cement from limestone Salt Uranium

33. 07.16.b Observe this sequence of sedimentary layers Medium to dark gray shale with fossil marine organisms Sandstone, mudstone, coal Sandstone with marine shells Sedimentary units with fossilized wood and dinosaur tracks