interior of the earth.ppt

8/10/2019 INTERIOR OF THE EARTH.ppt

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INTERIOR OF THE EARTH

EVIDENCE

LAYERSSUBLAYERS


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Different Evidence

Laboratory measurements of P & S waves

Applied Reflection Seismology

Meteorites

Volcanism


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Seismic Evidence - Body

Waves


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TYPES OF WAVES


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NATURE OF ROCKS AND

WAVES Direct relation between velocity and

density

Direct relation between velocity and rigidity

Inverse relation between velocity andincompressibility


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PRESENCE AND ABSENCE OF

WAVES


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PATH OF WAVES IN

HETEROGENOUS MEDIUM


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REFRACTION OF S WAVES


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REFRACTION OF P WAVES


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SHADOW ZONE


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Wave Velocity & Interior


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BODY WAVES & LAYERS OF

EARTH


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http://whatonearth.olehnielsen.dk/interior.asp


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SIESMIC WAVES AND

INTERIOR OF EARTH


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http://www2.ocean.washington.

edu/oc540/lec01-1/


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Layered Structure of Earth


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LAYERS OF THE EARTH


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CRUST

Continental Crust

Oceanic Crust


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Main Features

Extent

Density

Temperature

Composition

Sub Layers-

1-sial

2- sima

Conard discontinuity


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CONTINENTAL CRUST-

FORMATION Overall material with granitic composition.

Other rock types are basalts, but volumetrically not important.

Velocity of seismic waves increase with depth, because of a downwards

increase in basaltic rocks.

thickest beneath mountain ranges (50-60 km), elsewhere the thickness isabout 30 km.

The oldest continental crust is about 3.8 b.y. old, and continents keep

growing.

within the crust of each continent we can distinguish three basiccomponents: shields, stable platforms, and folded mountain belts.


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COMPOSITION OF CRUST

ELEMENT % BY WEIGHT

O 46.6

Si 27.7

Al 8.1

Fe 5.0

Ca 3.6

Na 2.8

K 2.6

Mg 2.1

TOTAL 98.5


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GROWTH OF CONTINENTS


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Variety of Continental crust

Velocity of P wave in different regioms

a- Wisconsin Shield, b-Basin-Range province , c-North Scotland, d- S California Mnt belt, e- Central Andese Mnt.Ocean-continent convergence, f- Central alps. Continent- Cont. convergence.


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Oceanic Crust

COMPOSITION AND STRUCTURE


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COMPOSITION AND STRUCTURE

OF OCEANIC CRUST The top layer (1.)consists of pelagic sediments that were

deposited above the basalts of the oceanic crust.

(2.)consists of lavas called pillow basalts,

(3.) consists essentially of complexly cross-cutting, nearvertical basaltic dikes, which are the feeder channels for thepillow basalts.

(4.)consists of the magma chambers that feed the dikes oflayer three, or are filled by the plutonic equivalent of basalt,gabbro.


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FORMATION OF OCEANIC

CRUST


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interior of the earth.ppt

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