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84 Cards in this Set
- Front
- Back
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Forming Sedimentary Rocks |
1. Weathering 2. Erosion 3. Deposition 4. Lithification |
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Two Types of Weathering |
1. Physical Weathering 2. Chemical Weathering |
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Physical Weathering |
Plant roots grow through soil, breaking rocks Frost Wedging: little bit of watet in cracks refreezing. Potholes |
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Chemical Weathering |
More common Different minerals are more sucseptible |
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Saprolite |
Rock that has undergone chemical weathering |
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Erosion |
Sediment transportation Water, wind, gravity, glaciers |
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Depositon |
Sediment is placed somewhere. Requires a Basin Results in layers, strata, beds |
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Accomadation space |
How much sediment a basin can hold |
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Subsidence |
Lowering of ground level as a result of depostion. Results in more accomodation space. |
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Lithification |
Hardening of sediment into rocks. Compaction and Cementation |
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Compaction |
Layering up of rocks over time, squeezing them together. High pressure, but not enough. |
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Cementation |
As pressure builds on rocks, water is squeezed out, leaving behind chemicals. The chemicals bind the rocks |
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Classifications of Sedimentary Rocks |
1. Detrital (clastic) 2. Chemical 3. Biogenic |
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Detrital (Clastic) Sediment |
Based on grain size: Gravel, sand, silt, clay Look at Sorting and Rounding |
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Sorting (clastic rocks) |
How similar in size the grains are. The better sorted, the more time in erosion (farther traveled) |
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Rounding (detrital rocks) |
How smooth/rounded the sediments are. The smoother, the more erosion |
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Chemical Sediments |
Formed from chemical reactions. Usually just 1 major mineral type Economically viable |
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Biogenic Sediments |
Biological sources: Scallops die and fall to ocean floor, plants don't fully decay. |
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Mass wasting |
Landslides, very preventable |
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Causes of Slope Destabilization |
1. Angle of Repose 2. Lack of moisture 3. Excessive moisture 4. Lack of vegetation 5. Excessive vegetation |
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Angle of repose |
How steep slope is. Slopes can only get so steep, 35° good bet (not really) |
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Lack of Moisture |
Less moisture, particles cant stick together. Sandcastle with dry sand |
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Excessive moisture |
Sediment turns to mud, mud flows easily |
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Lack of vegetation |
Roots hold soil together, witbout them soil crumbles |
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Excessive vegetation |
Plants can draw moisture out of soil, drying it out. Also plants add a lot of weight. |
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Classifying mass wasting |
Based on: Material (mud, stone, ice) Type of movement (roll, slide) Speed |
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Creep |
Type of mass wasting. Inches per year, fence on a hill |
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Preventing Mass Wasting |
Drainage control Decrease steepness of slope Retaining Walls Rock Bolts |
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Structural Geology |
Formation of rocks, rocks getting deformed. Not hills, canyons, valleys |
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Types of Tectonic Forces |
1. Tensional 2. Compressional 3. Shearing Line up with plate boundaries. |
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Tensional Force |
Rock is pulled in two directions, opposite sides |
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Compressional Force |
Rock gets pushed in from opposite sides |
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Shearing Force |
Two sides of a rock slide past eachother |
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Rock responses to stress |
Brittle Ductile Rock type, T/P, speed of deformation |
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Types of Geologic Structures |
1. Folds 2. Joints 3. Faults |
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Folds |
Wavy pattern Common Compressional |
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Antiform Fold |
Arch shaped |
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Synform Fold |
Bowl, U shaped |
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Anticline Folds |
Oldest rocks are in center, getting hugged |
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Syncline Folds |
Oldest rocks are on outside |
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Horizontal Folds |
Rocks are neat. Parallel from above |
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Plunging Folds |
More common, rocks all crazy |
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Joints |
Brittle rocks cracked Very common Forms in multiples |
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Faults |
Inches to miles in length Classified by slip direction. 1. Dip-slip 2. Strike-slip |
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Types of Dip-slip Faults |
1. Normal 2. Reverse 3. Thrust |
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Normal Fault |
Hanging wall (wall on top) goes DOWN |
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Reverse Fault |
Hanging Wall (wall on top) goes UP |
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Thrust Fault |
Similat to reverse, but fault plane is almost flat. Hard to identify. SUBDUCTION ZONES |
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Strike-Slip Faults |
1. Left-lateral 2. Right-lateral |
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Focus |
Point on fault where motion occurs, underground |
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Epicenter |
Spot on ground above focus |
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P-Waves |
Compressional wave Does not cause motion on ground Fastest wave: 6-7 Km/s |
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S-Waves |
Shear wave, up and down motion Slower than P waves: 2-3 Km/s Does not move through fluids |
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S Wave Shadow Zone |
Since s waves can't pass through liquids, don't move through fluid outer core of planet. |
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L-Waves |
Surface waves, not very deep 3D motion, vertical and side to side |
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3 myths about detecting/measuring earthquakes |
1. Solo machines (actually groups of 3) 2. Old-Fashioned (not a roll of paper getting pulled, modern devices) 3. Swinging needles (needle never moves, rest of device moves) |
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How to find focus of earthquake |
Use differnce in arrival time of waves to multiple statements |
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Mercalli Index |
Uses roman numerals Based on cost of damage done |
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Richter Scale |
How much ground shaking occured Logarithmic Not used by scientists anymore |
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Problems of Richter Scale |
Can't study past earthquakes If seismometer gets turned off, no way of knowing Too complicated |
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Moment Magnitude |
How far the rocks moved from focus Fixes problems of Richter Scale |
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Liquefaction |
Loose, waterlogged sediment gets shook: Turns it to mud, buildings sink |
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2 Dating Methods |
1. Relative 2. Absolute |
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Stratigraphy |
Study of Strata Used to relative date |
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Unconformities |
Any gaps in time in layers of strata |
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Causes of Unconformities |
1. Run out of sediment 2. Run out of accommodation space 3. Sediment gets eroded |
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Types of Unconformities |
1. Disconformity 2. Nonconformity 3. Angular Unconformity |
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Disconformity |
Different rocks above and below, but same type (igneous, sedimentary) |
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Nonconformity |
Different rock types above and below |
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Angular Unconformity |
Rocks below are tilted, rocks above are straight Takes millions of years |
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Principle of Orginal Horizontality |
Rocks layers always initially form horizontally. So a non-horizontal layer has been altered earlier in time |
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Principle of Superposition |
Layer on top is youngest, layers on bottom is oldest So layers not following this have been effected |
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Principle of Cross-Cutting |
When rock cuts through another rock, the rock getting cut is older, rock cutting is younger |
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Principe of Faunal Succesion |
Order of which animals appear in rocks. Older rocks means older animals |
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Traits of Good Index Fossils |
1. Numerous 2. Widespread 3. Went extinct quickly 4. Easy to identify |
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Lithostratigraphy |
Correlate based on rock type. Match sandstone with sandstone |
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Sequence Stratigraphy |
Correlation based on unconformities Useful in areas with lots of unconformities like beaches |
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Chemostratigraphy |
Correlate based on chemicals in rock Iridium is very rare in rocks, so a spike in on area can be used to correlate |
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Magnetostratigraphy |
Look at magnetic properties in rocks Good for igneous rocks (MOR) |
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4 Eons |
1. Hadean 2. Archean 3. Proterozoic 4. Phanerzoic |
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Hadean |
4.5 Ga - 4.0 Ga Theia Impact, density stratification |
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Archean |
4 Ga - 2.5 Ga Very first fossils Continental crust is forming |
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Proterozoic |
2.5 Ga - 550 Ma Oxygen is beginning to form in atmosphere |
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Phanerzoic |
Fossil record diversifies 3 Eras: 1. Paleozoic 2. Mesozoic 3. Cenozoic |
