CATASTROPHIC EVENT NOTES (PART I):

What is one common cause behind all of these natural disasters:

Tornadoes, Hurricanes, Earthquakes, Volcanoes… Answer…. CONVECTION!

I.  CONVECTION: The transfer of heat by movement in fluids. (in both liquids & gases!) Warm fluids go up & cold fluids go down.

A.  Rising heated air causes tornadoes & hurricanes

B.  Rising heated magma causes plate movements in the earth’s crust

II.  EARTH’S LAYERS:

A.  Crust: The thin layer of rock on the outside

B.  Mantle: Melted rock layer that contains convection currents

C.  Inner & Outer Core – Very hot, made of iron & nickel

III.  PLATE TECTONICS:

A.  This theory states the Earth’s crust is made of rigid pieces called plates that float on the dense layer of melted rock beneath

B.  Wegener called this continental drift

C.  How plates move: convection currents cause hot material to rise & then circle back down when it cools, dragging the crust along with it as it moves.

D.  Evidence of Pangaea (the landmass that existed when all continentswere

joined, about 200 million years ago):

1.  matching fossils on separate continents

2.  sea floor spreading (Older crust is pushed farther away from the ridge.)

IV. EARTHQUAKES:

A.  Parts of an earthquake:

1.  focus – the point BENEATH the earth’s surface where an earthquake begins

2.  epicenter – the place ON THE EARTH’S SURFACE, directly above the focus

B.  Where do earthquakes happen?

1.  Most occur along the edges of the moving plates

2.  About 90% of the world’s earthquakes occur along the “Ring of Fire,” a region that surrounds the Earth’s Pacific Ocean.

3.  In the US, Alaska & California are the most active areas because the Pacific plate is pushing past the North American plate.

V.  SEISMIC WAVES are the waves that are generated by an earthquake.

There are 2 kinds that we need to know:

A.  P-waves (Primary waves)

1.  These are the fastest waves and

arrive 1st at seismographic stations.

2.  These are compression waves à

B.  S-waves (Seconday waves)

1.  These are slower than P-waves & arrive

2nd at seismographic stations.

2.  These are transverse waves à

C.  Scientists can tell how far away an earthquake is by looking at the difference in

P & S wave arrival times.

ß If the P & S arrival times are close together, the earthquake is close,

1. 

ß If the P & S arrival times are farther apart, the earthquake is farther away.