Plate Tectonics and Earthquakes Objectives Students will learn

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)

Continental Drift vs. Plate Tectonics – The Debate Alfred Wegener 1912 - observed the possible fit between So. America and Africa. • Hypothesized the continents were all together forming the supercontinent Pangaea – 250 million years ago • Supported by the following evidence: • fossil evidence • lithologic evidence • climatic evidence Pangaea Wegener became the laughing stalk of the science world – WHY?

Continental Drift vs. Plate Tectonics – The Debate Mid-Atlantic Ridge • 1947 – mapping of the ridge • linear mountain range • active EQ and volcanism • area of sea floor spreading Sea Floor Spreading • Magma rises in between the ocean floor (ridge). • Magma pushes the ocean floor – spreading the floor apart. Can scientists actually see “spreading” of the ocean floor? How do scientists know the floor is actually moving?

Paleomagnetism --- the evidence that the sea floor is active and moving (by the late 1960’s) Paleomagnetism: paleo (past) magnetism (magnetic) • past magnetism of lava flows are recorded on the sea floor • Iron in magma will point to the current north pole. Evidence shows north pole switches location to the south pole over geologic time (magnetic reversals). North reversal creating magnetic reversals on both sides of the plate (pattern of stripes) magnetic pattern South reversal 13

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. • Ridgid 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 – 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 Rise Fall

’s h t ar ce a f ur S E 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 • 0 o latitude = equator Longitude: • meridian lines that move east and west • 0 o 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 -55 S-lat, -15 W-long C E

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.