Geology Test 2 Review
Terms
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- Uniformiterianism (Actualism)
- "the same natural laws that exist today and govern the earth has governed the earth forever.
- Types of dating
- Relative & Absolute
- Relative Dating
- Original Horizontality, Superposition, Lateral Continuity, Cross cutting relationships
- Original Horizontality principle
- when beds are forming they are originally deposited horizontally
- Superposition principle
- older rocks on the bottom, younger rocks on top
- Lateral continuity principle
- normally bed extends laterally until in pinches out to nothing ex. Mt St Helens ash. If it ends in a blunt/cut off end then something must have happened to it.
- Cross cutting relationships principle
- a geological feature that cuts across rock is younger that the rock it cuts across – a dike is younger than the layers that it cuts across – the fault is younger than the rock it cut through
- Inclusions principle
- fragments that are included in the host rock are older than the host rock - ex. Xenoliths
- Unconformities
- "a surface where there is a gap in the geologic record “Time is missingâ€
- Angular unconformities
- "beds below the unconformity are not parallel to the beds above the
- Non Conformity
- sediments are deposited on intrusive igneous or metamorphic rocks
- Disconformity
- rock layers above & below the unconformity are all parallel. – one way to tell if time is missing – if one layer that has fossils is next to a layer that also has fossils of different time period.
- Correlation
- determining the time equivalency of rock units using Physical continuity, Rock types, Fossils
- Absolute dating
- Isotopic and Radioactive decay
- Isotopic Dating
- Parent, Daughter, half life
- Radioactive Decay
- Alpha Decay, Beta Decay, electron capture
- Geological Structure
- Stress & Strain
- Stress
- force acting on a rock
- Strain
- change in shape and or size of a rock as a result of stress
- Types of Stress
- Compression, tensional stress, shear
- Types of deformation
- Elastic, Ductile, Brittle Deformation
- Compression Stress
- pushing together - stress results in shortening strain
- Tensional Stress
- pulling apart – results in extensional (lengthening) strain
- Shear force Stress
- parallel forces pushing in opposite direction
- Elastic deformation
- Rocks return to their original shape or dimension after stress is released
- Ductile deformation
- fold or bend – rocks that are like playdough – it will not go back to its original shape
- Brittle Deformation
- breaks rocks
- Folds
- bend in rock units – results from ductile deformation
- Types of folds
- Anticline, Syncline, Plunging, Structural dome, Structural basin
- Anticline fold
- Upward arching fold
- Syncline fold
- trough shaped – downward arching
- Plunging fold
- axis is not horizontal
- Structural dome fold
- all beds dip away from a central point
- Structural basin fold
- all beds are toward a central point (salad bowl)
- Shapes of folds
- Open Folds, Isoclinal folds, Overturned folds, Recumbent folds
- Open folds
- less intense stress
- Isoclinal folds
- intense stress – ie: Christmas ribbon candy
- Overturned Fold
- shear stress or unequal compressive stress
- Recumbent Fold
- formed in the center of mountain ranges where there is a lot of crustal shortening (Himalayas)
- Parts of a fold
- Limbs, Axis, Axial plane
- Fractures
- Break in a rock, result of brittle deformation
- Kinds of fractures
- Joint, Fault
- Parts of a fault
- Fault Plane, Fault Trace, Hanging wall, Foot wall
- Best places to observe faults
- Roadcut, quarries, sea cliffs
- Types of faults
- Dip Slip Fault, Strike Slip Fault
- Types of Dip Slip Faults
- Normal, Reverse, Thrust
- Earthquakes occur when
- the stress exceeds rupture strength of rock, Stress exceed friction between the rocks on opposite sides of fault, mass changes
- Parts of an Earthquake
- Focus, Epicenter, fault trace
- Focus
- Point on a fault where the first movements take place
- Epicenter
- Point on earth's surface directly above the fault
- Seismology
- Study of Earthquake waves
- Types of earthquake waves
- Body waves - p & s waves Surface waves - Raleigh & love waves
- P Wave
- Compressional waves - push pull movement - travels through solids & liquids
- S Wave
- Shear waves - side to side motion - only travels through solids
- Raleigh waves
- Surface wave - up & down movement - like being on a ship - SS Raleigh
- Love waves
- Surface wave - side to side movement - causes the most damage
- Seismograph
- Instrument used to measure earthquake waves - has to be anchored in bedrock
- Inertia
- An object at rest tends to stay at rest
- Which wave is faster
- P wave is faster that S wave
- Equation determine distance earthquake
- ts-tp=d(1/rs-1/rp)
- Number of recording Seismograph
- Need minimum of 3 recording seismographs to determine epicenter of earthquake
- Measuring wave
- Can only measure distance not direction of waves
- Earthquake Size
- Intensity & Magnitude
- Intensity of Earthquake
- What you feel
- Magnitude of Earthquake
- measure of total energy released in a earthquake
- How do you measure Magnitude
- Richter Scale, Moment Magnitude
- Earthquake Damage
- Ground shaking, Tsunami, Liquification, Landslides
- Predicting Earthquakes
- Microseisms, Water well levels, animal behavior, Paleoseismology
- Way to tell what’s under surface of earth
- Earthquake waves, Volcanoes Kinder light, Physics Laws
- Classical Layers of earth defined by
- defined by the composition of layers
- Classical Layers of earth
- Crust, Mantle, Core
- Oceanic Crust
- thin, dense, Rock - Mafic, basalt/gabbro, Minerals – amphiboles, plagioclase, olivenes, pyroxene
- Continental Crust
- thick, Less dense than oceanic crust, Rock – Felsic, grantite/rhyolite, Minerals – quartz, k Spar, micas
- Mantle
- denser, Rock – ultramafic, peridotite, Minerals – olivine – pyroxene, garnet
- Core
- Very dense, mostly iron (Fe) – a little O, S, Si
- MoHo
- boundary between crust & mantle where seismic waves speed up.
- ULVZ
- Ultra Low Velocity Zone – Seismic waves slow down
- Geophysical Layers - defined by
- Defined by the state that the matter is in
- Geophysical Layers
- Lithosphere, Asthenosphere, Mesophere,Outer Core, Inner Core
- Lithosphere
- Crust and the upper mantle, Solid
- Asthenosphere
- Extends from the base of the lithosphere to depth of 660 km, Plastic – flows very slowly
- Mesophere
- Solid – due to pressure
- Outer Core
- Liquid - because it is liquid we have a magnetic field
- Inner Core
- Solid – because of pressure
- Isostacy
- Balance of equilibrium of blocks of crust, the crust is very thick under mountains, Crust will rebound with pressure off
- Magnetic Field
- Region of magnetic force that surrounds the earth, Generated by convection currents in the outer core, Polar reversals
- Paleomagnetism
- Study of ancient magnetic fields, Curie Point - magnets lose magnetism - 580, When cooled - magnet points in direction of pole