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Pgs. 135 - 137. Earthquake discoveries near and far. Discoveries of Earth’s Interior. Seismologists learn about the Earth’s interior by observing how seismic waves travel through the Earth.

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Pgs 135 137

Pgs. 135 - 137

Earthquake discoveries near and far


Discoveries of earth s interior
Discoveries of Earth’s Interior

  • Seismologists learn about the Earth’s interior by observing how seismic waves travel through the Earth.

  • Seismic waves will bend as they travel through different layers of rock, much like a straw in a glass of water.

  • Where waves bend in different directions, let seismologists know where layers of rock change.


Discoveries
Discoveries

  • The Moho is a place within the Earth where the speed of seismic waves increases sharply.

  • This is the boundary between the crust and mantle.

  • The shadow zone is an area on the Earth’s surface where no direct seismic waves can be detected.

  • This is evidence of a liquid core.

  • The solid inner core was discovered in 1936 by studying seismic waves, disproving the idea of a liquid core.


Quakes and shakes on other cosmic bodies
Quakes and Shakes on other Cosmic Bodies

  • Seismologist apply what they have learned about Earth to planets, moons, and stars.

  • They learn about their interiors by how waves move through them .

  • Some of the discoveries were found on the moon, Mars and the Sun.


The moon
The Moon

  • When man landed on the moon for the first time, they left a seismograph.

  • When they returned they purposely crashed their vehicle into the moons surface to create artificial seismic waves.

  • They found that the seismograms lasted over 90 minutes, much longer than any Earthquake.

  • The length suggests a different compositionthan on Earth.


Mars

  • In 1976, scientists sent a space probe to Mars with a seismograph on it.

  • When it landed, we found that Mars was very windy.

  • The seismograph was detecting the wind because it was that intense.

  • They have recorded one Marsquake though.

  • It shook the seismograph harder than any wind recorded.


The sun
The Sun

  • Scientists have studied seismic waves on the sun by using a satellite called SOHO.

  • Solar flares, powerful magnetic disturbances in the sun, produce seismic waves.

  • The solar flares can result in sunquakes.

  • Sunquakes can release about 1 million times the energy of a strong earthquake.


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