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Earth Structure (Internal Structure of the Earth (CRUST
depth- 50km
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Earth Structure
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facts
P and S waves gradually increase in velocity because crustal rocks become less compressible and more rigid with depth
at a depth of 30km, they both dramatically speed up as they enter the upper mantle. Geologists call this seismic boundary the Moho Discontinuity
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S- waves cannot be detected within a particular area (S-wave shadow zone) due to the presence of liquid in the Earth. Located at 11000km at an angle of 103 degrees
when P-waves enter the outer molten core, they slow down and reappear at a depth of 16000km or an angle at 142 degrees
waves
primary
- compressional wave
- velocity determined by incompressibility
- velocity in the crust = 6kms-1
- travel through all materials
secondary
- shear wave
- velocity determined by rigidity
- velocity in the crust = 3kms-1
- travel through solids and semi-solids
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The Earth has it's own magnetic field which is evidence that the Earth's outer core must be composed of molten iron which creates electro-magnetic energy when it is moving
solar system is full of debris that is believed to be remnants of a planet that existed between the orbits of Mars and Jupiter. When this debris collides with Earth, they burn in the atmosphere creating fiery streaks called meteors (shooting stars)
close resemblance between rocky meteorites and peridotite demonstrates that the planet had a mantle similar in composition to the Earth
2 types:
- rocky meteorites composed of rock similar to mantle peridotite
- iron and nickel meteors