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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 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. • 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 • 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 • 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 • 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 • 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.
