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Dr. Isiorho, IPFW 1 Geology G100 Quick review for Test #2.

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Presentation on theme: "Dr. Isiorho, IPFW 1 Geology G100 Quick review for Test #2."— Presentation transcript:

1 Dr. Isiorho, IPFW 1 Geology G100 Quick review for Test #2

2 Dr. Isiorho, IPFW2 Sedimentation and Sedimentary Rocks What is a sedimentary rock? What is a sedimentary rock?

3 Dr. Isiorho, IPFW3 Sediments Sediments are loose fragments of solid materials- pre- existing rocks, remains of organisms, and precipitation of minerals Sediment textures- size, shape, and arrangement Sediment textures- size, shape, and arrangement  are determined by transportation and depositional processes Sorting Sorting  selecting particle based on size, shape and density Shape Shape  angular or irregular grains become rounded  longer travels lead to more rounding of grains

4 Dr. Isiorho, IPFW4 From Sediments to Sedimentary Rocks Pressure, heat, and underground circulating water produce changes in rocks- known as Diagenesis Pressure, heat, and underground circulating water produce changes in rocks- known as Diagenesis Lithification- conversion of loose sediments into solid sedimentary rocks Lithification- conversion of loose sediments into solid sedimentary rocks  Compaction- weight of overlying materials  Cementation- mineral precipitated in pore spaces  Recrystallization- less stable minerals change to new stable minerals

5 Dr. Isiorho, IPFW5 Sedimentary Structures Physical features that reflect condition of deposition (how and where?) Beddings (stratification) Beddings (stratification)  sediments in distinct layers- separate depositional environments Graded beddings Graded beddings  deposition occurs in relatively quiet waters Cross bedding Cross bedding  sedimentary layers at an angle to underlying layers Ripple marks Ripple marks  small surface ridges- produced by water or wind  Symmetrical & Asymmetrical Mud crack Mud crack  muddy sediments that dry and contracts Bioturbation Bioturbation No drawing provided  No drawing provided 

6 Dr. Isiorho, IPFW6 Classification of Sedimentary Rocks Detrital and Chemical Detrital- based on grain size Detrital- based on grain size  Mudstone - clay and silt size- constitute > 50% of all detrital sedimentary rocks  Shale - clay and silt size particles- parallel layers- fissility  Siltstone - silt size particles  Sandstone - quartz arenite, arkose (with ~ 25% feldspar), graywacke (lithic, dark fragments & fines)  Breccia - angular gravel size particles  Conglomerate - rounded gravel size particles

7 Dr. Isiorho, IPFW7 Sed. rock Classification contd. Chemical- organic and inorganic Chemical- organic and inorganic Organic- derived from living organism/biogenic Organic- derived from living organism/biogenic  Limestone and chert- composed of skeletal remains of animals  coal- carbon rich remains of terrestrial plants Inorganic Sedimentary Rocks Inorganic Sedimentary Rocks  Direct precipitation from water  e.g. Limestone, chert  Evaporation of saline water  evaporite- gypsum, halite, dolostone

8 Dr. Isiorho, IPFW8 Sedimentary Environments Continental Continental  rivers, lakes, caves, desert, glaciers- mostly detrital Transitional- coastal- along ocean shores Transitional- coastal- along ocean shores  estuaries and deltas Marine Marine  shallow-above continental shelf (< 200m (700’))  deep- beyond the continental shelf Sedimentary Facies - sediments deposits at the same time but in different environments as a horizontal continuum of distinct rock type Sedimentary Facies - sediments deposits at the same time but in different environments as a horizontal continuum of distinct rock type

9 Dr. Isiorho, IPFW9 Metamorphic Rocks Altered rocks Altered rocks

10 Dr. Isiorho, IPFW10 Definitions Metamorphic rock is formed when existing rocks change due to subjection to pressure and or temperature Metamorphic rock is formed when existing rocks change due to subjection to pressure and or temperature  Any rock can undergo metamorphism Metamorphism is the process by which heat, pressure, and chemical reactions deep within the earth alter the mineral content and or structure of existing rock without melting it down Metamorphism is the process by which heat, pressure, and chemical reactions deep within the earth alter the mineral content and or structure of existing rock without melting it down

11 Dr. Isiorho, IPFW11 What Drives Metamorphism Heat Heat  Accelerate pace of chemical reactions Pressure Pressure  Lithostatic (confining)- rock becomes smaller and denser  Directed- minerals become aligned- Foliation Circulating Fluids Circulating Fluids  Ions in water- change mineral composition Parent Rocks Parent Rocks  Original rock’s composition will affect the outcome of metamorphism

12 Dr. Isiorho, IPFW12 Types of Metamorphism Contact Contact  Heat is the dominant factor  Area affected generally smaller than regional metarmorphism Regional are two types with extensive coverage Regional are two types with extensive coverage  Burial- occurs in deep sedimentary basins- no plate tectonics involved  Dynamothermal- occurs where converging plates squeeze a rock caught between them Others Others  Hydrothermal- involves hot water from magma  Fault-zone- rocks grinding past one another  Shock- meteorites strike  Pyrometamorphism- lightning

13 Dr. Isiorho, IPFW13 Metamorphic Rock Types Foliated- based on type of foliation Foliated- based on type of foliation  Slate- fine grain  Phyllite- fine grain with sheen  Schist- has ‘split’ appearance  Gneiss- layers/bands of minerals Non-foliated- based on mineral composition Non-foliated- based on mineral composition  Marble  Quartzite  Hornsfel Mixed Rock Mixed Rock  Migmatite- indicates partial melting

14 Dr. Isiorho, IPFW14 Metamorphism Temperature & Pressure Information about degree to which a metamorphic rock differs from its parent material Information about degree to which a metamorphic rock differs from its parent material Metamorphic Grade- Metamorphic Grade-  low ( ) slate  high ( ) gneiss Index minerals/metamorphic Zones are used to determine metamorphic condition of temperature and pressure Index minerals/metamorphic Zones are used to determine metamorphic condition of temperature and pressure  Chlorite, muscovite-low grade (low P/T)  Garnet, staurolite- intermediate  Sillimanite- high grade (high P/T)

15 Dr. Isiorho, IPFW15 How old is the Rock? How can we tell the age of rocks? How can we tell the age of rocks? Geochronology Geochronology

16 Dr. Isiorho, IPFW16 Geochronology Geochronology is the study of time in relation to earth’s existence Geochronology is the study of time in relation to earth’s existence Relative Dating Relative Dating  Determines how old a rock is in relation to its surrounding Numerical Dating (Absolute Age?) Numerical Dating (Absolute Age?)  Determines actual age in years

17 Dr. Isiorho, IPFW17 Relative Dating Relies on Key Principles such as Uniformitarianism - the present is key to the past Uniformitarianism - the present is key to the past Original horizontality Original horizontality  Sediments deposited in horizontal layers Superposition Superposition  Youngest rocks are on top (assuming no tectonic activity) Cross-cutting relationships Cross-cutting relationships  Cut layer is older than ‘cutting’ rock Faunal succession Faunal succession  Organisms succeed one another in recognizable reproducible pattern Unconformity Unconformity  Represents a break (gap) in the rock record

18 Dr. Isiorho, IPFW18 Numerical Age Isotope Dating relies on the rate of decay of radioactive isotopes within a rock Isotope Dating relies on the rate of decay of radioactive isotopes within a rock Radioactive isotopes have nuclei that spontaneously decay emitting or capturing a variety of subatomic particles Radioactive isotopes have nuclei that spontaneously decay emitting or capturing a variety of subatomic particles Decaying radioactive isotope- parent isotopes decay to form daughter isotopes Decaying radioactive isotope- parent isotopes decay to form daughter isotopes Half-life- is the time it takes for half the atoms of parent isotope to decay Half-life- is the time it takes for half the atoms of parent isotope to decay Some radioactive isotopes with daughter products Some radioactive isotopes with daughter products  U-238 => Pb-206; K-40 => Ar-40; C-14 => N-14

19 Dr. Isiorho, IPFW19 Factors Affecting Isotope Dating Results Isotope dating is more useful for igneous rocks Isotope dating is more useful for igneous rocks  Clock is set when igneous rock crystallizes locking the radioactive isotopes within its crystal lattice Rock/Mineral must be a closed system Rock/Mineral must be a closed system  Atoms of parent and daughter are still present in rock/mineral being dated Condition of parent Material Condition of parent Material  Fracture, weathering and migrating ground water Age of Substance Age of Substance  Enough measurable daughter isotope, use appropriate radioactive isotope

20 Dr. Isiorho, IPFW20 Other Numerical Dating Techniques Fission Track Fission Track  High speed particles emitted during radiation may pass through crystal leaving ‘tears’ within the crystal- the older the rock, the more fission tracks Dendrochronology (Tree-Ring dating) Dendrochronology (Tree-Ring dating)  Annual growth rings Varve- deposited layers of lake-bottom Varve- deposited layers of lake-bottom  Paired layers of sediments Lichenometry Lichenometry  Lichens grow at a fairly constant rate Cosmogenic isotopes Cosmogenic isotopes  Used in dating land features

21 Dr. Isiorho, IPFW21 Geologic Time Scale Contrasting several dating techniques chronicling Earth’s history to produce a geologic Time Scale Contrasting several dating techniques chronicling Earth’s history to produce a geologic Time Scale Geologic Time Scale- divided into Eons, Eras, Periods, and Epoches Geologic Time Scale- divided into Eons, Eras, Periods, and Epoches Phanerozoic Eon (evidence of life began) divided into three eras Phanerozoic Eon (evidence of life began) divided into three eras  Paleozoic (ancient life) dominated by marine invertebrates  Mesozoic (middle life) dominated by reptiles  Cenozoic (recent life) dominated by mammals

22 Dr. Isiorho, IPFW22 The Earth moves It’s not an earthquake…but the earth materials It’s not an earthquake…but the earth materials

23 Dr. Isiorho, IPFW23 Mass Movement Process that transports Earth’s materials downslope by the pull of gravity Process that transports Earth’s materials downslope by the pull of gravity  Friction, strength, and cohesiveness of materials resist mass movement  Angle of slope (sloppiness), water content, lack of vegetation, and biological disturbances enhance mass wasting

24 Dr. Isiorho, IPFW24 Causes of Mass Movement Steepness of Slope Steepness of Slope  Faulting, folding, river cut, glacial, coastal wave create steep slope Composition of Material either promotes or resists mass wasting Composition of Material either promotes or resists mass wasting  Solid /Unconsolidated Vegetation- lack of which promotes mass wasting Vegetation- lack of which promotes mass wasting Water Content- increases weight of material and reduces friction between planes of weakness Water Content- increases weight of material and reduces friction between planes of weakness Human/Other Disturbances Human/Other Disturbances

25 Dr. Isiorho, IPFW25 Triggers for Mass Movement Events Natural Triggers Natural Triggers  Climatic- torrential rains and snow melt  Geologic- earthquakes and volcanic eruptions Human-Induced Triggers Human-Induced Triggers  Oversteeping of slopes- excavation  Overloading- excess water, building, and other construction  Deforestation/overgrazing of vegetation  Loud noise- trains, aircrafts, blasting

26 Dr. Isiorho, IPFW26 Mass Wasting Types Classification is based on composition and velocity Classification is based on composition and velocity Creep- slowest form Creep- slowest form Slides- move along a plane of weakness Slides- move along a plane of weakness Slumps- move along concave slip surfaces Slumps- move along concave slip surfaces Flows- rocks and soils have with excess water Flows- rocks and soils have with excess water Falls- fastest type Falls- fastest type Landslide is a general term for downslope movement Landslide is a general term for downslope movement

27 Dr. Isiorho, IPFW27 Reducing Mass Movement Avoiding Avoiding  Predicting mass movement  Terrain analysis, field visit, eye witness/recorded accounts  Vegetation- over grazing, harvesting Preventing Preventing  Develop Prevention Plan  Enhance Forces that Resist or Reduce forces of mass wasting  Structural Approach- reduce slope  Non-Structural Approach- tree, chemical stability

28 Dr. Isiorho, IPFW28 Study for Test #2 Use the class notes/textbook and the links provided in the syllabus. Use the class notes/textbook and the links provided in the syllabus. It’s an open book test and the “Honor System” prevails…no help from any one, no collaboration It’s an open book test and the “Honor System” prevails…no help from any one, no collaboration

29 Dr. Isiorho, IPFW29 Some key words for Test #2 Some key words for test #2 Some key words for test #2 Cementation, crystallization, Compaction Cementation, crystallization, Compaction Transportation of sediments results in….. Transportation of sediments results in….. Rock salt, sandstone, siltstone, coal, arkose, graywacke Rock salt, sandstone, siltstone, coal, arkose, graywacke Quartzite, marble, slate, schist, migmatite, order of metamorphism Quartzite, marble, slate, schist, migmatite, order of metamorphism Types of metamorphism, parent materials of some metamorphic rocks Types of metamorphism, parent materials of some metamorphic rocks Relative age and principles of Superposition, original horizontality, faunal succession, cross-cutting, unconformities, radiometric dating, half life.. Relative age and principles of Superposition, original horizontality, faunal succession, cross-cutting, unconformities, radiometric dating, half life..


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