87 Cards in this Set
| Front | Back |
|---|---|
|
Earthquake
|
The result of stress building up within rock layers from lithospheric plate movement causing rock to break or slip along faults
|
|
What is a high risk area for earthquakes in the U.S.?
|
San Andreas Fault (Transform-- strike-slip)
|
|
Faults
|
Large planar fractures along which rocks move
|
|
Focus
|
The source of an earthquake
|
|
Epicenter
|
At the earth's surface just above the focus where the earthquake is felt
|
|
Elastic Rebound
|
As rocks on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded.
|
|
Hanging Wall
|
Body of rock above the fault
|
|
Footwall
|
the body of rock below the fault
|
|
Seismology
|
the study of earthquake waves
|
|
Seismographs
|
Instruments that measure earthquake waves as a series of squiggle lines from vibrations (these lines are called seismograms)
|
|
Seismic Waves
|
the energy created and released when rock masses suddenly move deep within the earth in response to tectonic stress
|
|
Body waves
|
radiate outward from the focus in all directions and travel through solid rock
|
|
P-waves
|
- compressional (longitudinal)
- seismic wave that induces the particles in the rock to vibrate back and forth in the same direction the wave moves
- "Push-and-Pull" waves
- Speeds of 15,000 mph (double that of S-waves)
|
|
S-waves
|
- causes the rock to vibrate at right angles to the direction of wave travel
-HALF as fast as P-waves
|
|
Surface Waves
|
- the SLOWEST seismic waves
- travel outward on earth's surface from the epicenter (much like ripples do when a stone is thrown into water)
- create most of the damage at the earth's surface because they produce the most ground movement and pass through areas the most slowly
|
|
Which waves pass through liquid core?
|
P-waves DO
S-waves DO NOT
|
|
True or False: P and S waves originate from the focus simultaneously.
|
TRUE
|
|
True or False: P and S waves reach the various seismograph stations at the same time.
|
FALSE. P and S waves travel at different speeds so even though they may originate at the same point in time they do not reach their final destination at the same time.
|
|
True or False: The farther the station from the focus, the farther apart the waves are when they arrive.
|
TRUE
|
|
How are seismic waves used to determine the location earthquakes originate from?
|
CALLED TRIANGULATION:
1. Time interval used to plot a travel-time curve on a graph (determining how far the station is from the earthquake)
2. Radius around 3 stations drawn
3. Where the 3 circles overlap is where the earthquake originated
|
|
How is earthquake size determined?
|
By measuring intensity and magnitude
|
|
The Mercalli Scale
|
- ranks intensity from 1-12 according to the amount of the resulting damage
- not a great system because it's dependent on the type of design and construction of building, etc.
|
|
Charleston Earthquake
|
The Charleston Earthquake of 1886 was a powerful intraplate earthquake that hit Charleston, South Carolina, and the East Coast of the US.
- demonstrated the Mercalli Scale being described as "vibrating buildings all the way in Chicago"
|
|
Richter Scale
|
A numerical scale that lists earthquake magnitudes in logarithmic (a value of 3 on a scale has a vibration 10x than that of a 2).
|
|
Subduction Boundary
|
oceanic crust of one plate is pushed underneath the continental or oceanic crust of another plate
|
|
Collision Boundary
|
two continental plates pushed together
|
|
Divergent Boundary
|
Crustal plates that move away from one another
|
|
Transform Boundary
|
Two plates move past each other
|
|
Liquefaction
|
- Shaking causes water movement in pores, reducing friction between grains, breaking their bonds
- major cause of building collapse
|
|
What mass movements are triggered by earthquakes?
|
- Rockfalls
- Slides
- Avalanches
- Tsunamis (faulting causes sea floor displacement, making large waves)
|
|
Deformation
|
A change in shape, position, or orientation of a material by bending, breaking or flowing
|
|
What are the 4 components of deformation?
|
1. Translation
2. Rotation
3. Strain
4. Volume Change
|
|
Stress
|
Force: F=ma; F=mg where g=9.8 m/s^2
|
|
Confining Stress
|
Stress equal from all directions
|
|
Differential Stress
|
Stress not equal from all directions
- Tensional <-- [ ] -->
- Compressional --> [ ] <--
- Shear -->
[ ]
<--
|
|
Strain
|
A change in size, shape, or volume of a material
|
|
Stages of Deformation
|
- Elastic Deformation (Reversible; non-permanent strain)
- Plastic Deformation (Irreversible; permanent strain)
- Fracture
|
|
Materials of Deformation: Brittle
|
have a small or large region of elastic behavior but only a small region of plastic behavior before they fracture
|
|
Materials of Deformation: Plastic
|
have small region of elastic behavior and a large region of ductile behavior before fracturing
|
|
Horst & Graben Faults
|
Blocks bounded by normal faults
(see notes)
|
|
Folds
|
Syncline: dip down (valley shape)
Anticline: dip upward (hill shape)
|
|
Relative Dating
|
- "This" is older than "that"
- using stratigraphy & fossils
|
|
Absolute Dating
|
- "this" is 50 billion years old
- Radiometric dating
|
|
Stratigraphy (Stratigraphic Relationships - Relative Dating)
|
1. Superposition
2. Original Horizontality
3. Cross-cutting relationships (dikes, faults, uncomformities)
4. Inclusions
|
|
Law of Superposition
|
Lower beds in sequence of undeformed sedimentary rocks came first and are therefore older than the rocks overlying them
|
|
Principle of Original Horizontality
|
Layers of sediment are deposited in a flat-horizontal position
|
|
Principle of cross-cutting relationships
|
the feature that cuts across another (the cutter) is always younger than the thing cut (the cuttee)
Things that cut:
- dikes, sills
- intrusions
- faults
- uncomformities
|
|
Uncomformities
|
Erosional surfaces that cut across rocks and mark periods when there was no deposition
3 types:
1. Disconformity: Layers parallel below and above uncomformity
2. Angular uncomformity: Layers below uncomformity not parallel to the layers above it
3. Nonconformity: igneous and/or meta…
|
|
Principle of Fossil Succession
|
- fossils succeed one another in a definite order
- can order strata by non-repeating groups of fossils
- fossils are non-repeating because of extinction
|
|
Index fossils
|
Fossils used to correlate different strata and identify different geologic periods
|
|
Fossils
|
Remains of past life
|
|
What conditions lead to preservation of fossils?
|
- hard parts of an organism
- rapid burial of the organism
- marine environment preserves more due to steadier sedimentation and fewer erosive agents
|
|
Kinds of fossil preservation
|
- ulaltered remains: calcareous shells
- permineralization: silification
- replacement: pyritization
- molds and casts
- carbonization
- unaltered remains: frozen
- unaltered remains: low oxygen, peat bog people
- trace fossils
|
|
Absolute Dating
|
Absolute dating is the process of determining an approximate computed age in archaeology and geology.
|
|
Radioactivity (Absolute Dating)
|
when an atomic nuceli breaks apart (decays because the protons and neutrons aren't able to bind together)
|
|
Types of Radioactive Decay
|
- alpha emission: emission of 2 protons and 2 neutrons
- beta emission: an electron is given off from the nucleus
- electron capture: an electron is captured by the nucleus
|
|
Parent Isotope
|
an unstable radioactive isotope
|
|
Daughter Isotope
|
isotope resulting from the decay of the parent
|
|
Parent-Daughter Pairs
|
Carbon 14 - Nitrogen 14
Uranium 238 - Lead 206
Potassium 40 - Argon 40
|
|
Shortest Half-Life Parent-Daughter Pair
|
Carbon 14 - Nitrogen 14
|
|
Half-Life
|
time it takes for half of parent atoms to decay to daughter atoms
|
|
Short Half-Life
|
fast rate of decay
|
|
Long Half-Life
|
Slow rate of decay
|
|
Longest Half-Life Pair
|
Rubidium 87 - Strontium 87
|
|
Rocks best for Radiometric Dating
|
Best: Igneous
Medium: Metamorphic
Worst: Sedimentary
|
|
Geologic Time Scale
|
- Precambrian: 4.56 bya - 545 mya
- Phanerozoic Eon: abundant life; 545 mya - 0 (today)
- Paleozoic Era: marine, land, colonization, fish, amphibians, reptiles
- Mesozoic Era: dinosaurs, birds, mammals begin
- Cenozoic Era: age of mammals, ice age
|
|
First Supercontinent
|
Rodina
|
|
Second Supercontinent (After Rodina)
|
Pangea
|
|
Third Supercontinent (After Pangea)
|
Mesozoic-Gondwana
|
|
Hydrologic Cycle
|
water temporarily stored in reservoirs and is transported into and out of the atmosphere, geosphere, and biosphere
|
|
What are the 5 processes of the hydrologic cycle?
|
1. Evaporation: water evaporates into the atmosphere (mostly from the oceans)
2. Transpiration: water released into the atmosphere by plants
3. Precipitation: water condenses into clouds in the atmosphere and falls as precipitation (rain or snow)
4. Infiltration: water that is precipit…
|
|
What is water infiltration or runoff the land dependent on?
|
1. intensity and duration of the rainfall
2. how wet the soil already is
3. the soil texture
4. the slope of the land
5. the amount and type of vegetation
|
|
What circumstances lead to water being infiltrated into the ground?
|
The LOWER the intensity, the SHORTER the duration, the DRIER the soil, the COARSER the texture, and the SHALLOWER the slope, the MORE WATER IS INFILTRATED.
|
|
3 Zones of Groundwater
|
1. soil moisture zone
2. saturation zone
3. unsaturated zone
|
|
Interaction Between Groundwater and Streams
|
1. streams gain water from the ground water = "gaining streams"
2. streams lose water to the ground water = "losing streams"
3. combination of 1 & 2 in that in some sections it is a gaining stream and in others a losing stream
|
|
True or False: Water moves from areas where the water table is high to zones where the water table is lower.
|
TRUE
|
|
What is the movement of groundwater, its amount, and rate, influenced by?
|
1. Porosity: open spaces in rock
2. Permeability: ability to transmit water
|
|
What has greater porosity, well sorted sediment or poorly sorted sediment?
|
Well sorted sediment
|
|
What factors affect metamorphic grade?
|
- heat
- pressure
- moisture
|
|
Metamorphism
|
Metamorphism is the change of minerals or geologic texture in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change).
|
|
Metamorphic Grade
|
A measure of the relative intensity of metamorphism
- low grade = small changes to rock's texture and mineralogy (150-200 degrees C)
- high grade = extreme changes to rock's texture and mineralogy
|
|
Does metamorphism differ from melting and crystallization?
|
Metamorphism includes recrystallization but not melting as it is a SOLID STATE transformation
|
|
Contact vs. Regional Metamorphism
|
Contact Metamorphism:
- affects a small area
- occurs at high temperature, low pressure
Regional Metamorphism:
- affects a large area
- occurs at high temperature, high pressure, and shear stress
|
|
Foliation
|
The parallel alignment of mineral grains in a rock caused by direct stress
|
|
Slaty Cleavage
|
- Type of foliation
- Parallel alignment of mainly mica minerals
- Low grade metamorphism
|
|
Schistocity
|
- Parallel to sub-parallel foliation of medium to coarse grained minerals
- intermediate - high grade metamorphism
|
|
Gneissic Layering
|
- Light and dark layering due to mineral segregation
- Intermediate - high grade metamorphism
|
GEOL 120: EXAM 2