Lecture 2: Seismology and the Earth's layers Flashcards
Seismic waves
Ground vibration produced by an earthquake
P-wave
First type of seismic wave to arrive at a seismograph from the focus of an earthquake; a type of compressional wave
S-wave
Second type of seismic wave to arrive at a seismograph from the focus of an earthquake; a type of shear wave
Density
Mass per cubic volume of a substance
Elasticity
Ability of an object or material to resume its normal shape after being stretched or compressed
Bulk modulus
Strength of rock in response to stretching/squeezing
Shear modulus
Strength of rock in response to shearing force
Seismic discontinuity
Boundary between 2 layers with different properties (different seismic wave velocities)
Refraction
Wave changes angle
Reflection
Some energy reflected
Transformation
Some energy transformed into other kind of wave
Moho
Mohorovicic discontinuity–crust-mantle boundary (sudden compositional change)
Gabbro
Dark-grey, coarse-grained igneous rock containing an abundance of mafic materials, especially pyroxene
Peridotite
Coarse-grained, greenish-grey, ultramafic intrusive igneous rock composed primarily of olivine; dominant rock of mantle and source rock of basaltic magmas
Cratonic keels
Mechanically stable and chemically distinct portion of mantle that extends 200-300km beneath a craton into the asthenosphere
Earthquake
Violent motion of the ground that occurs when brittle rock under stress suddenly breaks along a fault
Thermal boundary layer
Boundary depends on local temp gradient, not chemical composition
Olivine
Mg2SiO4
Ophiolite suite
Old oceanic crust lifted onto continent
Xenolith
Piece of rock within an igneous mass which is not derived from the original magma but has been introduced from elsewhere
Meteorite
Fragment of rock from asteroid belt
