GS2: Physical Layers

Geologists use seismic waves for

determining the composition of Earth's interior

shadow zone

an area on earths surface where no direct seismic waves from a particular earthquake can be detected;

lithosphere

solid layer; outermost layer

asthenosphere

plastic-like layer (below the lithosphere)

mesosphere

solid Earth layer between the asthenosphere and the outer core

outer core

Earth's only liquid layer;

inner core

solid sphere of metal, mainly iron and nickel, at Earth's center

evidence for lithosphere's physical properties

directly observable; seismic waves travel quickly here

evidence for asthenosphere's physical properties

seismic waves slow down here; must be going thru a material that's a liquid-like solid

evidence for mesosphere's physical properties

seismic waves speed up here; must be going thru a material that's a hard solid

evidence for liquid outer core

p waves slow down and refract at ~105 degrees and leave p wave shadow zones; s waves don't travel through at ~105 and leave a big s wave shadow zone

evidence for a solid inner core

seismic waves can travel through it; Earth's magnetic field;

seismogram

the record of an earthquake's seismic waves produced by a seismograph

refraction

to bend light or sound

reflection

to throw back light, heat, or sound without absorbing it