Ch. 2.1 and 2.2 Lecture PPT
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Transcript of Ch. 2.1 and 2.2 Lecture PPT
EarthquakesEarthquakes:
the shaking and trembling that results from the movement of rock beneath Earth’s surface
See simulation below:
Terashake
Caused by STRESS
Stress: a force that acts on rock to change its shape or volume
1. Shearing
pushes a mass of rock in two opposite directions
Causes rock to break and slip apart or to change its shape
See simulation below: http://scign.jpl.nasa.gov/learn/plate5.htm
2. Tension
Pulls on the crust
Stretching rock so that it becomes thinner in the middle
See simulation below:
http://scign.jpl.nasa.gov/learn/plate5.htm
3. Compression
Squeezes rocks until it folds or breaks
Compresses rock like a giant trash compacter
See simulation below:
http://scign.jpl.nasa.gov/learn/plate5.htm
What is a Fault?A break in Earth’s crust
Slabs of crust slip past each other
Occurs along a plate boundary
Forces of plates: compress, pull, or shear the crust so it breaks
Types of Faults Normal- caused by tension
Reverse- caused by compression
Strike-slip -caused by shearing
Fault Movements
See simulation below:
Mountain Building From faulting
Two normal faults
From folding Anticline - forms
an arch Syncline - forms a
bowl
Plateau - large area of flat land From vertical fault
Earthquake Terminology
Focus Point beneath
Earth’s surface where rock that is under stress breaks, triggering an earthquake
Epicenter Point on the
surface directly above the focus
Seismic Waves P Waves First waves to
arrive
Compress and expand the ground like an accordion
Can travel through solids and liquids
Seismic Waves S Waves Vibrate from
side to side as well as up and down
Only move through solids, not liquids
Seismic Waves Surface waves Move slower
than P and S waves
They produce the most severe ground movements
Some roll like ocean waves
Others shake from side to side
Wave MovementsSee simulation below:
Detecting Seismic Waves
Seismograph Records and
measures the vibrations of seismic waves
Measuring Earthquakes Magnitude - measurement of
earthquake strength based on seismic waves and movement along faults
Mercalli Scale - rate earthquakes according to their intensity How affect people buildings, people
and land surface Richter Scale - rating of the size of
seismic waves as measured by a particular type of seismograph
Moment Magnitude Scale - estimates the total energy released by an earthquake