Transcript seismic waves

EARTHQUAKES!!!
Earthquakes
• Earthquake: Sudden movement of rock
sliding along a fault in the earth’s crust
• Releases energy as this occurs.
• Energy release produces strong vibrations
called seismic waves.
Energy Release
• Edges of the plates get stuck while
the rest of the plate keeps
moving.—Energy stored up
• When the force of the moving
blocks finally overcomes the friction
of the jagged edges of the fault and
it unsticks, all that stored up energy
is released.
• The energy radiates outward from
the fault in all directions in the form
of seismic waves like ripples on a
pond. –This is the earthquake
Earthquake Waves
• Focus- point of
earthquake origin
• Epicenter- point
on earth’s surface
above the focus
• Primary Waves ( P-wave)
– Travel through solids and
liquids
– Travel FAST!
• Secondary Waves
(S-waves)
– Only travel through solids
– Travel SLOWER
than P-waves
 Longitudinal Waves
(L-waves)
-- Travel on earth’s surface
http://losangeles.cbslocal.com
3/17 la eq
http://earthguide.ucsd.edu/mystery_detectives/teach/epi
center/ia_graph_travel_time_animation.html
Mystery Earthquake animations:
http://earthguide.ucsd.edu/mystery_detectives/teach/epi
center/show.html
TO know the
EPICENTER:(where quake
started)
• Seismic waves radiate out from the source
in all directions.
• Siesmograph stations recieve p and s
waves and use the difference in arrival
time to determine the distance away.
• Different stations compare the information
recorded at the same time.
Seismic Station picks up p and s
waves and determines they came from
an earthquake 10 km away.
But 10 km
from which
direction?
A second seismic station records the same
quake at 5 km away.
This narrows down the epicenter to 2 spots.
To pinpoint the epicenter,
3 seismic stations must record
the quake. (triangulation)
VOLCANOES
• A hole in Earth’s crust through which lava
flows from underground.
Origin of Magma
• Molten rises from the
Earth’s
asthenosphere (upper
mantle) to the Earth’s
surface through
cracks creating a
volcano.
Most volcanoes occur along plate
boundaries
Hot Spots
•
Volcanically active sites that arise in places
where large quantities of magma move to the
surface in large, column-like plumes
– Can occur away from plate boundary
– When under a oceanic plate, volcanic island
chains forms
• Mountains—folding and faulting; convergent
continental boundaries
• Plateau– eroded mountain