(5 12 09) How Earthquakes Work
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Transcript of (5 12 09) How Earthquakes Work
How Earthquakes Work
Jordan ChairesP.4.
5-12-09
How Does an Earthquake Work?An earthquake is a vibration that travels
through the earth's crust.
Causes of EarthquakesAll kinds of things can cause earthquakes:movements of the earth's platesvolcanic eruptions meteor impacts underground explosions (an underground
nuclear test, for example) collapsing structures (such as a collapsing
mine)
Steps to an Earthquake
Plate Movement
s
Seismic
Waves
Destruction to
families, homes,
and contries
FactsAn Earthquake occurs about once every 11
seconds.There have been more than 1.5 million
earthquake-related fatalities in the last hundred years.
Plate TectonicsSeismology - the study of earthquakes The basic theory is that the surface layer of
the earth (lithosphere) is comprised of many plates that slide over the athenosphere layer.
CollideAt the boundaries between these huge plates
of soil and rock, three different things can happen: divergent plate boundary (Plates can move
apart)convergent plate boundaries (Plates can
push together)transform boundaries (Plates slide against
each other)
FaultsFaults are formed where these plates meetFaults are breaks in the earth's crust where
the blocks of rock on each side are moving in different directions
Earthquakes are most common along fault lines
Seismic WavesWhen a sudden break or shift occurs in the
earth's crust, the energy radiates out as seismic waves, just as the energy from a disturbance in a body of water radiates out in wave form.Primary waves – can travel through solid, liquid
and gas, and so will pass completely through the body of the earth. Typically arrive at the surface as an abrupt thud.
Secondary waves - don't move straight through the earth. They only travel through solid material, and so are stopped at the liquid layer in the earth's core
SeismographA seismograph is a machine that registers the
different waves.
The Richter ScaleThe Richter Scale is used to rate the amount of energy it released.
The wave amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake. The largest earthquake on record registered an 9.5 on the currently used Richter Scale.
The Richter Scale
ConclusionEarthquakes are mainly formed by the
movements of the earth's plates. They occur all the time but not all of them
result in major destruction or fatalitiesSeismographs measure earthquakes