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39 Cards in this Set
- Front
- Back
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what is a divergent boundary
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where new crust is generated as the plates pull away from each other.
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What are convergent boundaries
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where crust is destroyed as one plate dives under another.
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What are transform boundaries
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where crust is neither produced nor destroyed as the plates slide horizontally past each other.
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what are plate boundary zones
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broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.
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what is seismology
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the study of vibrations that are produced by earthquakes, the impact of meteorites, or artificial means such as an explosion.
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What are seismic waves
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the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.
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What are body waves
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Traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. These waves are of a higher frequency than surface waves.
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What are primary waves
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This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. Also known as compressional waves, because of the pushing and pulling they do
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What are secondary waves
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the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium.S waves move rock particles up and down, or side-to-side--perpindicular to the direction that the wave is traveling in
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What are surface waves
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Travelling only through the crust, surface waves are of a lower frequency than body waves, and are easily distinguished on a seismogram as a result. Though they arrive after body waves, it is surface waves that are almost enitrely responsible for the damage and destruction associated with earthquakes.
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What are love waves
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It's the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal motion.
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What are rayleigh waves
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A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves.
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Earth's core
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Convection within outer core
Result of heat released from Earth’s core Solid inner core detached from mantle Inner core rotates at different rate. generates earths magnetic field |
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Lower mantle
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Mantle below is solid but deforms plastically due to high temperature and pressure
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Asthenosphere
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Partially melted with slow convection
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Lithosphere/Crust
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“Floats” on asthenosphere
Continental and Ocean Crust float at different elevations due to Isostasy “Slides” over asthenosphere due to reduced friction at base of lithosphere |
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Earth Dynamics - Review
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Review
Solid inner core Liquid outer core - convection Solid lower mantle - slow deformation Partially melted asthenosphere - convection Rigid lithosphere - broken into moving plates |
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What is a Slump (Hazard resulting from the earthquake)
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Slumps
Rotational slide, material moves along a concave curved surface Moderate velocities |
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What is STRESS
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an applied force and its direction
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What is STRAIN
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a change of shape in response to an applied force
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What are three types of strain
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ELASTIC
PLASTIC BRITTLE |
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What is elastic deformation
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Reversible - the rock will return to its original shape when stress removed
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What is PLASTIC DEFORMATION
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Irreversible - the change in size and shape resulting from the stress is permanent
Results in folding Characteristic of deformation at high temperatures and pressures in the deep crust |
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What is BRITTLE DEFORMATION
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Rocks fracture when “elastic limit” exceeded
Results in faulting |
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What is a FAULT
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a fracture in rock along which movement has occurred
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What is FAULT RUPTURE
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the movement along a fault…
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What is FAULT PLANE
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the fractured surface (mostly or totally underground)
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Tensional stress makes...
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“Normal” faults
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Compressional stress makes...
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“Reverse” faults & thrust faults
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Lateral or shearing stress
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“Strike-slip” faults
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What is ELASTIC REBOUND
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The sudden release of energy built up over a long period of time by elastic deformation
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What is Focus
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Site of first motion along fault
Located at some depth below the surface |
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What is the EPICENTER
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Point on the surface directly above the focus
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What is FAULT RUPTURE
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Extent of surface along which fault
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Location of an earthquake is determined by...
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Time delay between arrival of P and S waves
Position of focus determined by minimum of three seismic stations |
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What is INTENSITY
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Measure of EFFECTS of an earthquake (human response and physical damage)
Does not require instruments Can be used for past earthquakes |
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What is MAGNITUDE
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measure of energy released
single number on log scale |
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What is Moment Magnitude
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Takes into account the extent of the fault rupture
Can be calculated from both seismic records and field measurements of fault rupture |
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Ways of PREDICTION
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Recognition of precurser events
Measurement of deformation - vertical and lateral movement Change in groundwater movement and rock permeability Foreshocks Animal behaviour |
