The Dynamic Crust Regents Earth Science. Seismic Waves and Earth’s Structure How can we tell that...
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Transcript of The Dynamic Crust Regents Earth Science. Seismic Waves and Earth’s Structure How can we tell that...
The Dynamic CrustThe Dynamic Crust
Regents Earth ScienceRegents Earth Science
Seismic Waves and Earth’s Seismic Waves and Earth’s StructureStructure
How can we tell that the outer core is liquid and the inner core is solid?
Seismic Waves and Earth’s Seismic Waves and Earth’s StructureStructure
Velocity of Seismic WavesVelocity of Seismic WavesP-waves travel fastest P-waves travel fastest (~2X faster than S-(~2X faster than S-
waves)waves)
S-waves second fastestS-waves second fastestIncreases in denser materialIncreases in denser materialThe waves are refracted (bent) as they The waves are refracted (bent) as they
pass from a material of one density to a pass from a material of one density to a material of a higher or lower density.material of a higher or lower density.
Seismic Waves and Earth’s Seismic Waves and Earth’s StructureStructure
P-wavesP-wavesTravel through
solids, liquids and gases
S-wavesS-wavesTravel only through
solids
Seismic Waves and Earth’s Seismic Waves and Earth’s StructureStructure
Scientists infer the properties of Earth's Scientists infer the properties of Earth's interior through the analysis of seismic interior through the analysis of seismic wave data.wave data.
By studying thousands of seismograms By studying thousands of seismograms scientists have discovered that seismic scientists have discovered that seismic waves refract, reflect, change velocity, waves refract, reflect, change velocity, and become absorbed by various parts of and become absorbed by various parts of Earth's interior.Earth's interior.
The following diagram shows the results of The following diagram shows the results of these thousands of studies.these thousands of studies.
P and S WavesP and S Waves
Seismic Waves and Earth’s Seismic Waves and Earth’s StructureStructure
P and S WavesP and S Waves
Shadow ZoneShadow Zone
The The Shadow ZoneShadow Zone is created by the is created by the refraction of P-waves and the refraction of P-waves and the inability of S-waves to travel through inability of S-waves to travel through a liquid.a liquid.
Inferred Properties of Earth’s Inferred Properties of Earth’s InteriorInterior
Inferred Properties of Earth’s Inferred Properties of Earth’s InteriorInterior
Earth’s Layers - DetailEarth’s Layers - Detail CrustCrust LithosphereLithosphere MohoMoho AsthenosphereAsthenosphere MantleMantle
Asthenosphere Asthenosphere (plastic)(plastic)
Stiffer MantleStiffer Mantle Outer CoreOuter Core Inner CoreInner Core
Earth’s CrustEarth’s Crust Continental Continental
CrustCrust Beneath continentsBeneath continents ThickerThicker
Thickest where Thickest where highest (beneath highest (beneath mountains)mountains)
Granitic RocksGranitic Rocks Less DenseLess Dense
Oceanic CrustOceanic Crust Beneath OceansBeneath Oceans ThinnerThinner
Basaltic RocksBasaltic Rocks DenserDenser
MOHOMOHO
Mohorovic DiscontinuityMohorovic DiscontinuityInterface between lithosphere and Interface between lithosphere and
asthenosphereasthenosphereBelow Moho rocks become denser due to Below Moho rocks become denser due to
increased pressure at depth and solid phaseincreased pressure at depth and solid phase
AsthenosphereAsthenosphere
Plastic portion of the upper mantlePlastic portion of the upper mantleRocks are partially molten (plastic)Rocks are partially molten (plastic)Detected due to decrease in velocity of Detected due to decrease in velocity of
seismic waves through this zoneseismic waves through this zoneWidely accepted theory that magma and Widely accepted theory that magma and
lava originate in the lava originate in the asthenosphereasthenosphere
Inferred Properties of Earth’s Inferred Properties of Earth’s InteriorInterior
Inferred Properties of Earth’s Inferred Properties of Earth’s InteriorInterior