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Relative susceptibility To weathering. Products of Weathering.

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Presentation on theme: "Relative susceptibility To weathering. Products of Weathering."— Presentation transcript:

1 Relative susceptibility To weathering

2 Products of Weathering

3 Factors influencing Weathering Rates 1.Rock structures – chemical/mineral composition, physical features 2.Topography 3.Climate 4.Vegetation 5.Time

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5 Sediments and Sedimentary Rocks

6 Sediments - unconsolidated particles created by 1. The weathering of rock 2. The secretions of organisms or decomposition of organic matter 3. Chemical precipitation

7 Sedimentary Rock Formation 1.Weathering – breakdown both physically (clasts) or chemically 2.Erosion – loosening of weathered products (clasts) and initial transport 3.Transportation – movement of materials via wind, water, or ice; sorting and rounding can occur 4.Deposition – material settles out of the transporting medium 5.Lithification – process of either cementation or compaction of the material

8 W. W. Norton

9 Sedimentary Rocks Composed of lithified sediments - by compaction – weight of overlying sediment compresses sediment, important in fine-grained sediments - by cementation – materials carried in solution precipitates minerals - iron oxides, carbonates, silica Two Classifications - clastic -nonclastic

10 Fig W. W. Norton

11 Sedimentary Rocks Clastic Rock – composed of fragments of preexisting rocks. Nonclastic Rock – composed of chemical precipitates or biochemical matter.

12 Daily Question Use a Venn diagram to compare and contrast clastic, chemical nonclastic, and biochemical nonclastic sedimentary rocks. Identify at least five characteristics. Clastic Chemical Biochemical

13 Types of Sediments - Clastic Broken fragments of rock produced by weathering. Classified according to size. Range in size from largest boulder to smallest clay particle.

14 The size, shape, and distribution of particles that collectively make up a rock Clastic Texture Increasing distance from source

15 Which sample is closer to the source of sediment?

16 Sorting - a function of transport mechanism 1. Water 2. Wind 3. Glaciers

17 Sorting by Wind

18 Fig. 7.26a Stephen Marshak

19 Fining up Graded Beds

20 Texture and Transport Distance In general, as transport distance increases, rounding and sorting increase. Examples: Breccia – cemented close to source Conglomerate – transported then cemented

21 Types of Sediments - Biogenic Terrestrial sediments - mainly plant matter ex. Coal Marine sediments - mainly carbonates Corals - large components of reefs. Bivalves, gastropods, foraminifers - whole or partial skeletons form sand and gravels. Algae, crinoids, echinoderms, bryozoans - disintegrate to form some sand particles and lime mud. Diatoms, Radiolaria – bedded chert sio 2

22 Coral (carbonate)

23 Foramanifera

24 Diatoms

25 Types of Sediments - Chemical Inorganic process, no biological activity involved. Formed by minerals precipitating from solution. i.e. – Ca 2+ + CO 3 2- = CaCO 3 Na + + Cl - = NaCl

26 Chemical Sediments 1.Terrestrial - Evaporites: Gypsum - CaSO 4. H 2 O Anhydrite -CaSO 4 Halite - NaCl

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28 Chemical Sediments 2. Marine Carbonates - CaCO 3 (limestone) Chert (Quartz) – SiO 2

29 Bedding – Layering or stratification in sedimentary rock

30 Fig. 7.25abc W. W. Norton

31 Cross Bedding – water or wind

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34 Ripple Marks

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36 Sedimentary Environments

37 Sedimentary Systems and Plate Tectonics


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