Presentation is loading. Please wait.

Presentation is loading. Please wait.

Geology G100 Quick review for Test #2

Similar presentations

Presentation on theme: "Geology G100 Quick review for Test #2"— Presentation transcript:

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

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

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

4 From Sediments to Sedimentary Rocks
Pressure, heat, and underground circulating water produce changes in rocks- known as Diagenesis 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 Dr. Isiorho, IPFW

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

6 Classification of Sedimentary Rocks
Detrital and Chemical 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 Dr. Isiorho, IPFW

7 Sed. rock Classification contd.
Chemical- organic and inorganic 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 Direct precipitation from water e.g. Limestone, chert Evaporation of saline water evaporite- gypsum, halite, dolostone Dr. Isiorho, IPFW

8 Sedimentary Environments
Continental rivers, lakes, caves, desert, glaciers- mostly detrital Transitional- coastal- along ocean shores estuaries and deltas 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 Dr. Isiorho, IPFW

9 Metamorphic Rocks Altered rocks Dr. Isiorho, IPFW

10 Definitions 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 Dr. Isiorho, IPFW

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

12 Types of Metamorphism Contact
Heat is the dominant factor Area affected generally smaller than regional metarmorphism 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 Hydrothermal- involves hot water from magma Fault-zone- rocks grinding past one another Shock- meteorites strike Pyrometamorphism- lightning Dr. Isiorho, IPFW

13 Metamorphic Rock Types
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 Marble Quartzite Hornsfel Mixed Rock Migmatite- indicates partial melting Dr. Isiorho, IPFW

14 Metamorphism Temperature & Pressure
Information about degree to which a metamorphic rock differs from its parent material Metamorphic Grade- low ( ) slate high ( ) gneiss 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) Dr. Isiorho, IPFW

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

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

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

18 Numerical Age 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 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 Some radioactive isotopes with daughter products U-238 => Pb-206; K-40 => Ar-40; C-14 => N-14 Dr. Isiorho, IPFW

19 Factors Affecting Isotope Dating Results
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 Atoms of parent and daughter are still present in rock/mineral being dated Condition of parent Material Fracture, weathering and migrating ground water Age of Substance Enough measurable daughter isotope, use appropriate radioactive isotope Dr. Isiorho, IPFW

20 Other Numerical Dating Techniques
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) Annual growth rings Varve- deposited layers of lake-bottom Paired layers of sediments Lichenometry Lichens grow at a fairly constant rate Cosmogenic isotopes Used in dating land features Dr. Isiorho, IPFW

21 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 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 Dr. Isiorho, IPFW

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

23 Mass Movement 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 Dr. Isiorho, IPFW

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

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

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

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

28 Study for Test #2 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 Dr. Isiorho, IPFW

29 Some key words for Test #2
Cementation, crystallization, Compaction Transportation of sediments results in….. Rock salt, sandstone, siltstone, coal, arkose, graywacke Quartzite, marble, slate, schist, migmatite, order of metamorphism 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.. Dr. Isiorho, IPFW

Download ppt "Geology G100 Quick review for Test #2"

Similar presentations

Ads by Google