1. Sedimentary Rocks Igneous are the most abundant rock type, but are not the ones we see the most… Sedimentary rocks cover approximately 5% of the earths surface, and cover over the majority of the igneous rocks.

2. Sedimentary Rocks are part of the rock cycle

3. What is sedimentary rock and why are they important?  Sedimentary rocks result from mechanical and chemical weathering  Comprise ~ 5% of Earth’s upper crust  Contain evidence of past environments  Record how sediment is transported  Often contain fossils

4. Why do we care about sedimentary rocks?  They are important for economic reasons because they contain  Coal  Petroleum and natural gas  Iron, aluminum, uranium and manganese  Geologists use them to read Earth’s history

5. Sediments  Pieces of solid material that have been deposited on earths surface by wind, water, ice, gravity, or chemical precipitation  Piecing all of these sediments together…makes a sedimentary rock.

6. Weathering – breaking rocks up  weathering - the physical and chemical breakdown of rock.  - Physical weathering is breakdown of rock by physical forces. Example: rock wedged apart by freezing water or by plant roots.  - Chemical weathering is breakdown of rock by chemical reactions. Examples: solution, oxidation, and hydrolysis reactions.

7. Physical weathering aka Mechanical weathering  1. Physical weathering is breakdown of rock by physical forces. Rocks may be broken apart along planes of weakness by…  Four types of mechanical weathering Frost wedging – freezing and thawing of water in cracks disintegrates rocks Unloading – exfoliation of igneous rocks at Earth’s surface due to reduction in pressure….Like peeling layers off an onion Thermal expansion – alternate expansion and contraction due to heating and cooling Biological activity – disintegration resulting from plants and animals

9. Chemical Weathering  Major processes of chemical weathering  Dissolution Aided by acid in water Soluble ions contained in underground water  Oxidation Chemical reaction where compound loses electrons Important in breaking down mafic minerals  Hydrolysis Reaction of any substance with water Hydrogen ion replaces other positive ions

10. Chemical Weathering  Chemical Weathering  Breaks down rock and minerals  Important agent in chemical weathering is water (transports ions and molecules involved in chemical reactions)

12. Rates of Weathering  Rates of weathering  Mechanical weathering aids chemical weathering by increasing surface area  Others factors affecting weathering  Rock characteristics Marble and limestone easily dissolve in weak acidic solutions

13. Erosion and transport  Weathering breaks the rocks up  Erosion takes them away Erosion: removal and movement of surface materials from one location to another is called erosion.  4 main agents of erosion Wind (sand dunes) Moving water (v-shaped valleys) Gravity (Rock falls) Glaciers (u-shaped valleys)

14. Deposition  Agents of erosion can carry sediments according to how strong they are: Ex: strong running rivers can carry HUGE boulders. Glaciers can move whole pieces of continents Wind can carry small sand grains and silt particles  When the strength of these agents of erosion dies down…they drop whatever they were carrying. DEPOSITION

15. Deposition  When do agents of erosion lose their strength? Rivers flow into a calm lake or ocean basin Winds die down  Drop off the heaviest sediments first Sorted vs. Unsorted  Sorted = all pieces same size. (wind and water)  Unsorted = not all same size. (glaciers and gravity)

16. Lithification – making of a rock  Compaction  Cementation – 2 common natural cements Calcite Iron oxide

17. Two Types of Sedimentary Rocks  Types of sedimentary rocks  Detrital rocks – transported sediment as solid particles  Chemical rocks – sediment that was once in solution

18. Detrital Sedimentary Rocks  Constituents of detrital rocks can include  Clay minerals  Quartz  Feldspars  Micas  Particle size is used to distinguish among the various types of detrital rocks

19. Detrital Sedimentary Rocks cont.  Common detrital sedimentary rocks (in order of increasing particle size)  Shale Mud-sized particles deposited in thin layers called laminae Most common sedimentary rock

20. Detrital Sedimentary Rocks cont.  Sandstone Made of sand-sized particles Forms in a variety of environments Sorting and composition of grains can be used to interpret the rock’s history Quartz is the predominant mineral (due to its durable nature)

21. Detrital Sedimentary Rocks cont.  Conglomerate and breccia Both composed of particles > 2mm in diameter Conglomerate consists largely of rounded clasts Breccia is composed of large angular particles

22. Sizes determine the classification of detrital sedimentary rocks This figure shows how clastic sediment of various sizes will, after compaction and cementation, form different types of detrital sedimentary rocks. The process of sediment turning into rock is called lithification.

23. Chemical Sedimentary Rocks  Precipitated material once in solution  Precipitation of material occurs two ways:  Inorganic processes  Organic processes (biochemical origin)  Common chemical sedimentary rocks  Limestone Most abundant chemical rock Made of the mineral calcite Marine biochemical limestones form as coral reefs, coquina (broken shells), and chalk (microscopic organisms) Inorganic limestones include travertine and oolitic limestone

24. Chemical Sedimentary Rocks  Common chemical sedimentary rocks  Dolostone Typically formed secondarily from limestone Common in ancient rocks, rare today  Chert Made of microcrystalline quartz Usually deposited as siliceous ooze in deep oceans (can be diatomaceous)

25. CHERT Diatomaceous chert TRAVERTINE FOSSILIZED LIMESTONE Coquina