Plate Tectonics and Earthquakes
Objectives:
• Students will learn key terms associated with
plate tectonic processes. (Part A)
• Students will understand the specific plate
motions associated with divergent,
convergent, and transform plate boundaries.
(Part B)
• Students will gain a global view of EQ’s
(where EQ’s typically occur). (Part C)
• Students will evaluate and apply concepts
from lab parts A, B, and C to answer critical
thinking questions. (Part D)
The Plate Tectonic Model
lithosphere
Volcanism
mantle)
Patterns Asthenosphere (upper
Earthquake
Patterns
• The plate tectonic model describes surface features, geologic
environments, and patterns of EQ’s and volcanism.
• Ridged lithospheric plates (continents + ocean floor) ride
along the soft layer (like hot wax) called the asthenosphere
• Plates spread apart, collide, and slide past one another.
• EQ’s, crustal deformation, and volcanism take place at plate
boundaries.
Plate Boundaries
Divergent Boundary – plates move AWAY from each other
Convergent Boundary – plates move TOWARD each other
Transform Boundary – plates SLIDE past each other
Divergent Boundary:
• Earthquake activity
• plate material separating
ocean plate divergence
Extensional forces
create EQ’s
continental divergence
Extension creates
faulting
Convergent Boundary:
• interaction of two plates moving toward one another
making contact– hence, collision or convergence
• collisions produce earthquakes, volcanic activity, and
crustal deformation
Ocean-Cont
Subduction
zone
Oregon-Washington
Coast
Ocean-Ocean
Subductioin
zone
Aleutian Island
(Alaska area)
Cont-Cont
Himalayan
Mountains
ocean-continent
• Earthquake activity
• thinner and more dense plate
subducts
• subducted plates melt (160 km)
below the surface, and magma
rises
• EQ’s occur along the subduction
zone, and magma plumes rise
• typically, the older plate will
subduct (more dense) beneath
younger plate material
ocean-ocean
• melting plate material rises,
creating volcanic arc systems
• most EQ’s occur within the
subduction zone
• two plates converge with the
same density
cont-cont
• same density prevents
subduction
• extensive deformation
Transform Boundary:
• two plates are sliding past one another
SAF
• lack the spectacular features associated with
divergent/convergent boundaries
• marked by linear valleys (slices through the
earth’s crust)
• shallow-focused EQ’s occur along the slip area of the
sliding plates
Transform boundaries offsetting
spreading ridges
• Typical EQ’s occur along
Earthquakes
the transform boundary.
Cross-sectional view of the SAF
and associated LA faults
•SAF – transform motion
•LA faults- vertical motion
Los Angeles
SAF-transform fault
What moves or drives the plates?
What could Wegener have told the geological society?
Only a Model – Think Convection
Convection – heat transfer through a liquid or gas that
results in circular movement of particles
Cooler water sinks
Hot water rises
Earth Crust
The Earth’s Mantle
Can you see the convection?
mantle
mantle
Rise
Fall
Mantle operates like a “lava lamp,” producing
swelling and shrinking of magma plumes.
57
Latitude and Longitude
• Where are you on earth?
Latitude/Longitude
• a grid system used to locate features on
the earth’s surface
Latitude:
• parallel lines that move north
and south
• 0o latitude = equator
Longitude:
• meridian lines that move east
and west
• 0o longitude is through
Greenwich, England
11
Los Angeles, Ca
Spokane, Wa
New York, NY
350 N-lat, 1210 W-long
470 N-lat, 1180 W-long
420 N-lat, 750 W-long
12
West
East
Latitude (+)
Longitude (+)
Latitude (+)
Longitude (-)
North
Equator
Prime Meridian
Latitude (-)
Longitude (-)
South
Latitude
Latitude
( (-)
Longitude (+)
13
52 N-lat, 78 E long
B
15 N-lat, -132 W-long
A
-25 S-lat, 136 E long
D
-18 S-lat, -162 W-long
E
-55 S-lat, -15 W-long
C
Plate Tectonics Lab:
• Part A: Plate tectonic definitions
• use lab text
• use textbook resources in classroom
• Part B: Identification of plate boundaries
• use lab text, colored pencils
• use textbook resources in classroom
• Part C: Plotting EQ location
• use provided long/lat handouts
• use colored pencils
• Part D: Critical thinking questions
• use parts A, B, and C and your
synthesizing brain.