Instant Download with all chapters and Answers
Sample Chapters
*you will get solution manuals in PDF in best viewable format after buy*
PLATE TECTONICS: A SCIENTIFIC
REVOLUTION UNFOLDS 2
INTRODUCTION
Plate Tectonics: A Scientific Revolution Unfolds covers the development of the Theory of Plate Tectonics and discusses the characteristics of this theory. The chapter opens with a discussion of Alfred Wegner’s hypothesis of continental drift, its supporting evidence, and its major criticisms. The chapter then discusses the development of the plate tectonics theory and the motions and characteristics of transform, divergent and convergent boundaries. The chapter then discusses modern evidence that confirms the theory, including ocean drilling, mantle plumes, paleomagnetism, polar wandering, magnetic reversals, and seafloor spreading. The chapter ends with a discussion of how plate motion is measured and an overview of the two hypothesized mechanisms of plate motion through movements of the mantle.
CHAPTER OUTLINE
1. From Continental Drift to Plate Tectonics
a. Early geology viewed the oceans and continents as very old features with fixed geographic positions
b. Researchers realized that Earth’s continents are not static; instead, they gradually migrate across the globe
i. Create great mountain chains where they collide
ii. Create ocean basins where they split apart
c. Tectonic processes deform Earth’s crust to create major structural features on Earth d. Scientific revolution
i. Began in 20th century with continental drift hypothesis—the idea that continents were capable of movement
ii. As more advanced, modern instruments came along, scientists evolved from the ideas of continental drift to the theory
2. Continental Drift: An Idea Before Its Time
a. Set forth by Alfred Wegener in his 1915 book, The Origin of Continents and Oceans
i. Challenged the long-held assumption that the continents and ocean basins had fixed geographic positions
ii. Suggested that a single supercontinent (Pangea) consisting of all Earth’s landmasses once existed
iii. Further hypothesized that about 200 million years ago, this supercontinent began to fragment into smaller landmasses
iv. These landmasses “drifted” to their present positions over millions of years.
b. Evidence: The Continental Jigsaw Puzzle
i. Similarity between the coastlines on opposite sides of the Atlantic Ocean led to the hypothesis that they were once joined
1. A very precise fit when the continental shelf boundary is considered the edge of the continent
c. Evidence: Fossils Matching Across the Seas
i. Identical fossil organisms had been discovered in rocks from both South America and Africa (Mesosaurus and Glossopteris)
ii. Some type of land connection was needed to explain the existence of similar
Mesozoic age life forms on widely separated landmasses iii. Wegener asserted that South America and Africa must have been joined, and closer to the South Pole during that period of Earth’s history
d. Evidence: Rock Types and Geologic Features
i. Rocks found in a particular region on one continent closely match in age and type those found in adjacent positions on the once adjoining continent
ii. Similar evidence found in mountain belts that terminate at one coastline and reappear on landmasses across the ocean
iii. When these landmasses are positioned as they were about 200 million years ago, as shown in Figure 2.6B, the mountain chains form a nearly continuous belt
e. Evidence: Ancient Climates
i. Evidence of vast ice sheets covering extensive portions of the Southern Hemisphere and India that presently lie in subtropic and tropical climates
ii. A global cooling event was rejected by Wegener because during the same span of geologic time, large tropical swamps existed in several locations in the Northern
Hemisphere iii. Can be explained by southern continents that were joined together and located near the South Pole
1. At the same time, this geography places today’s northern continents nearer the equator and accounts for the tropical swamps that generated the vast coal deposits
f. As compelling as this evidence may have been, 50 years passed before most of the scientific community accepted the concept of continental drift
3. The Great Debate
a. Rejection of the Drift Hypothesis
i. Main objections to Wegener’s hypothesis stemmed from his inability to identify a credible mechanism for continental drift
ii. Proposed that gravitational forces of the Moon and Sun that produce Earth’s tides were also capable of gradually moving the continents across the globe
iii. Also incorrectly suggested that the larger and sturdier continents broke through thinner oceanic crust, much like ice breakers cut through ice
b. Most of the scientific community, particularly in North America, either categorically rejected continental drift or treated it with considerable skepticism
4. The Theory of Plate Tectonics
a. New technology post-World War II gave science evidence to support some of Wegener’s ideas, and many new ideas
i. The discovery of a global oceanic ridge system that winds through all of the major oceans
ii. Studies conducted in the western Pacific demonstrated that earthquakes were occurring at great depths beneath deep-ocean trenches
iii. Dredging of the seafloor did not bring up any oceanic crust that was older than
180 million years iv. Sediment accumulations in the deep-ocean basins were found to be thin, not the thousands of meters that were predicted
b. Rigid lithosphere overlies weak asthenosphere
i. The crust and the uppermost, and therefore coolest, part of the mantle constitute
Earth’s strong outer layer, known as the lithosphere
1. Lithosphere varies in thickness depending on whether it is oceanic lithosphere or continental lithosphere
a. Oceanic crust thickest (100 kilometers) in deep ocean basins, but thinner along ridge system
b. Continental lithosphere averages 150 kilometers thick, and may extend to 200 kilometers beneath stable continental interiors
2. The composition of both oceanic and continental crusts affects their respective densities
a. Oceanic crust is composed of rocks having a mafic (basaltic) composition = higher density
b. Continental crust is composed largely of felsic (granitic) rocks = lower density
ii. The asthenosphere (asthenos = weak, sphere = a ball) is a hotter, weaker region in the mantle that lies below the lithosphere
1. Temperature and pressure put rocks very near their melting temperature; causes rocks in asthenosphere to respond to forces by flowing
2. The relatively cool and rigid lithosphere tends to respond to forces acting on it by bending or breaking, but not flowing
3. Earth’s rigid outer shell is effectively detached from the asthenosphere, which allows these layers to move independently
c. Earth’s major plates
i. The lithosphere is broken into about two dozen segments of irregular size and shape called plates that are in constant motion with respect to one another
ii. None of the plates are defined entirely by the margins of a single continent nor ocean basin
iii. Seven major plates: North American, South American, Pacific, African, Eurasian,
Australian-Indian, and Antarctic plates iv. Intermediate-sized plates: Caribbean, Nazca, Philippine, Arabian, Cocos, Scotia, and
Juan de Fuca plates
v. Several smaller microplates
d. Plate movement
i. Plates move as somewhat rigid units relative to all other plates
ii. Most major interactions among them (and, therefore, most deformation) occur along their boundaries
iii. Plates are bounded by three distinct types of boundaries differentiated by the type of movement they exhibit
1. Divergent plate boundaries—where two plates move apart, resulting in upwelling of hot material from the mantle to create new seafloor
2. Convergent plate boundaries—where two plates move together, resulting in oceanic lithosphere descending beneath an overriding plate, eventually to be reabsorbed into the mantle or possibly in the collision of two continental blocks to create a mountain belt
3. Transform plate boundaries—where two plates grind past each other without the production or destruction of lithosphere
iv. Divergent and convergent plate boundaries each account for about 40 percent of all plate boundaries
v. Transform faults account for the remaining 20 percent.
5. Divergent Plate Boundaries and Seafloor Spreading
a. Most divergent plate boundaries are located along the crests of oceanic ridges
i. Constructive plate margins—this is where new ocean floor is generated
ii. Two adjacent plates move away from each other, producing long, narrow fractures in the ocean crust
iii. Hot rock from the mantle below migrates upward to fill the voids left as the crust is being ripped apart
iv. Molten material gradually cools to produce new slivers of seafloor that forms between the spreading plates = spreading centers
b. Oceanic ridges and seafloor spreading
i. Ridges: elevated areas of the seafloor characterized by high heat flow and volcanism
1. Including the Mid-Atlantic Ridge, East Pacific Rise, and Mid-Indian Ridge
2. 2–3 kilometers high, 1000–4000 kilometers wide
3. Along the crest of some ridge segments is a deep canyon-like structure called a rift valley
ii. Movement at ridges is called seafloor spreading
1. Typical rates of spreading average around 5 centimeters (2 inches) per year
2. Slower along Mid-Atlantic Ridge; higher along East Pacific Rise
3. Generated all of Earth’s ocean basins within the past 200 million years iii. Creation of ridges at areas of seafloor spreading
1. Newly created oceanic lithosphere is hot, making it less dense than cooler rocks found away from the ridge axis
a. New lithosphere forms and is slowly yet continually displaced away from the zone of upwelling.
b. Begins to cool and contract, thereby increasing in density, which equals thermal contraction
c. It takes about 80 million years for the temperature of oceanic lithosphere to stabilize and contraction to cease
2. As the plate moves away from the ridge, cooling of the underlying asthenosphere causes it to become increasingly more rigid
a. Oceanic lithosphere is generated by cooling of the asthenosphere from the top down
b. The thickness of the oceanic lithosphere is age-dependent; that is, the older (cooler) it is, the greater its thickness
c. Oceanic lithosphere that exceeds 80 million years in age is about 100 kilometers thick: approximately its maximum thickness c. Continental rifting
i. Within a continent, divergent boundaries can cause the landmass to split into two or more smaller segments separated by an ocean basin
1. Begins when plate motions produce opposing (tensional) forces that pull and stretch the lithosphere
2. Promotes mantle upwelling and broad upwarping of the overlying lithosphere as it is stretched and thinned
3. Lithosphere is thinned, while the brittle crustal rocks break into large blocks
4. The broken crustal fragments sink, generating an elongated depression called a continental rift
5. Modern example of an active continental rift is the East African Rift
6. Convergent Plate Boundaries and Subduction
a. Total Earth surface area remains constant over time; this means that a balance is maintained between production and destruction of lithosphere
i. A balance is maintained because older, denser portions of oceanic lithosphere descend into the mantle at a rate equal to seafloor production
b. Convergent plate boundaries are where two plates move toward each other and the leading edge of one is bent downward, as it slides beneath the other
c. Also called subduction zones because they are sites where lithosphere is descending
(being subducted) into the mantle
i. Subduction occurs because the density of the descending lithospheric plate is greater than the density of the underlying asthenosphere
ii. Old oceanic lithosphere is about 2 percent more dense than the underlying asthenosphere, which causes it to subduct
iii. Continental lithosphere is less dense and resists subduction
d. Deep-ocean trenches are the surface manifestations produced as oceanic lithosphere descends into the mantle
i. Large linear depressions that are remarkably long and deep ii. Example: Peru–Chile trench along west coast of South America
e. The angle at which oceanic lithosphere subducts depends largely on its age and, therefore, its density
i. When seafloor spreading occurs near a subduction zone, the subducting lithosphere is young and buoyant, which results in a low angle of descent
ii. Older, very dense slabs of oceanic lithosphere typically plunge into the mantle at angles approaching 90 degrees
f. Types of convergence:
i. Oceanic–continental convergence: Oceanic crust converges with continental crust
1. The buoyant continental block remains “floating”; the denser oceanic slab sinks into the mantle
2. When a descending oceanic slab reaches a depth of about 100 kilometers (60 miles), melting is triggered within the wedge of hot asthenosphere that lies above it
a. Water contained in the descending plates acts as “wet” rock in a highpressure environment and melts at substantially lower temperatures than does “dry” rock of the same composition.
b. Partial melting: the wedge of mantle rock is sufficiently hot that the introduction of water from the slab below leads to some melting
3. Being less dense than the surrounding mantle, this hot mobile material gradually rises toward the surface
4. Examples include Andes of South America and Cascade Range of
North America
ii. Oceanic–oceanic convergence: Oceanic crust converges with oceanic crust
1. One slab descends beneath the other, initiating volcanic activity by the same mechanism that operates at all subduction zones
2. Volcanoes grow up from the ocean floor, rather than upon a continental platform
3. Will eventually build a chain of volcanic structures large enough to emerge as islands = volcanic island arc
4. Examples include the Aleutian, Mariana, and Tonga islands iii. Continental–continental convergence: Continental crust converges with continental crust
1. The buoyancy of continental material inhibits it from being subducted
2. Causes a collision between two converging continental fragments
3. Folds and deforms the accumulation of sediments and sedimentary rocks along the continental margins
4. Result is the formation of a new mountain belt composed of deformed sedimentary and metamorphic rocks that often contain slivers of oceanic crust
5. Example is the Himalayas created by collision of Indian and Asian continental landmasses
7. Transform Plate Boundaries
a. Where plates slide horizontally past one another without the production or destruction of lithosphere
b. Most transform faults are found on the ocean floor where they offset segments of the oceanic ridge system
c. Transform faults are part of prominent linear breaks in the seafloor known as fracture zones
i. Include both the active transform faults as well as their inactive extensions into the plate interior
ii. Active transform faults lie only between the two offset ridge segments and are generally defined by weak, shallow earthquakes
iii. Trend of these fracture zones roughly parallels the direction of plate motion at the time of their formation
d. Transform faults also transport oceanic crust created at ridge crests to a site of destruction
e. Most transform fault boundaries are located within the ocean basins; however, a few cut through continental crust
i. Example is San Andreas fault of North America—the Pacific plate is moving toward the northwest, past the North American plate
8. How Do Plates and Plate Boundaries Change?
a. The size and shape of individual plates are constantly changing
i. African and Antarctic plates are continually growing in size as new lithosphere is added to their margins
ii. Pacific plate is being consumed along its flanks faster than it is growing, so diminishing in size
b. Boundaries of plates also migrate
i. Peru–Chile trench migrating westward due to westward drift of South American
Plate relative to Nazca plate
c. Plate boundaries can be created or destroyed in response to changes in the forces acting on the lithosphere
d. The breakup of Pangea
i. Using modern tools geologists have recreated the steps in the breakup of this supercontinent, an event that began about 180 million years ago
ii. Important consequence of Pangaea’s breakup was the creation of a “new” ocean basin: the Atlantic
iii. Splitting of the supercontinent did not occur simultaneously along the margins of the Atlantic
1. First split developed between North America and Africa, began between 200 million and 190 million years ago
2. By 130 million years ago, the South Atlantic began to open near the tip of what is now South Africa
a. Led to the separation of Africa and Antarctica and sent India on a northward journey
3. 50 million years ago, India collided with Asia and created the Himalayans and the Tibetan Highlands
4. During past 20 million years,
a. Arabia has rifted from Africa to form the Red Sea
b. Baja California has separated
e. Plate tectonics in the future
i. Geologists have extrapolated present-day plate movements into the future
1. Along the San Andreas Fault, Los Angeles and San Francisco will pass each other in about 10 million years, and in about 60 million years the Baja Peninsula will begin to collide with the Aleutian Islands
2. Africa may continue northward and collide with Eurasia, resulting in the closing of the Mediterranean
3. North and South America will begin to separate, while the Atlantic and
Indian Oceans will continue to grow, at the expense of the Pacific Ocean
ii. A few geologists have even speculated on the nature of the globe 250 million years in the future
1. Atlantic seafloor will eventually become old and dense enough to form subduction zones around much of its margins
2. Atlantic will close, and collision of Americas with Eurasian–African landmasses will form the next supercontinent
3. Dispersal of Pangaea will end when the continents reorganize into the next supercontinent
iii. Projections must be viewed with skepticism, as many assumptions must be correct for the events to unfold as hypothesized
9. Testing the Plate Tectonics Model
a. Evidence: Ocean Drilling
i. The Deep Sea Drilling Project (1968–1983) sampled the seafloor to determine its age
1. Showed that the sediments increased in age with increasing distance from the ridge
2. Supported the seafloor-spreading hypothesis: youngest crust would be found at the ridge axis (where it is produced), oldest crust would be found adjacent to the continents
ii. Thickness of ocean-floor sediments provided additional verification of seafloor spreading
1. Sediments are almost entirely absent on the ridge crest and that sediment thickness increases with increasing distance from the ridge
iii. Reinforced the idea that the ocean basins are geologically young because no seafloor with an age in excess of 180 million years was found
b. Evidence: Mantle Plumes and Hot Spots
i. Mapping volcanic islands and seamounts (submarine volcanoes) of Hawaiian
Islands to Midway Islands revealed several linear chains of volcanic structures
ii. Radiometric dating of this linear structure showed that the volcanoes increase in age with increasing distance from the “big island” of Hawaii
iii. A cylindrically shaped upwelling of hot rock, called a mantle plume, is located beneath the island of Hawaii
1. Hot, rocky plume ascends through the mantle, the confining pressure drops, which triggers partial melting
2. The surface manifestation of this activity is a hot spot, an area of volcanism, high heat flow, and crustal uplifting that is a few hundred kilometers across
3. As the Pacific plate moved over a hot spot, a chain of volcanic structures known as a hot-spot track was built
iv. Supports ideas that plates move over the asthenosphere, which means that age of each volcano indicates how much time has elapsed since it was situated over the mantle plume
c. Evidence: Paleomagnetism
i. Rocks that formed thousands or millions of years ago and contain a “record” of the direction of the magnetic poles at the time of their formation
1. Earth’s magnetic field has a north and south magnetic pole that today roughly align with the geographic poles
2. Some naturally occurring minerals are magnetic and are influenced by Earth’s magnetic field (e.g., magnetite)
3. As the lava cools, these iron-rich grains become magnetized and align themselves in the direction of the existing magnetic lines of force
4. They act like a compass needle because they “point” toward the position of the magnetic poles at the time of their formation
ii. Apparent polar wandering
1. The magnetic alignment of iron-rich minerals in lava flows of different ages indicates that the position of the paleomagnetic poles has changed through time
a. Magnetic north pole has gradually wandered from a location near
Hawaii northeastward to its present location over the Arctic Ocean b. Evidence that either the magnetic north pole had migrated, an idea known as polar wandering, or that the poles remained in place and the continents had drifted beneath them
2. If the magnetic poles remain stationary, their apparent movement is produced by continental drift
a. Studies of paleomagnetism show that the positions of the magnetic poles correspond closely to the positions of the geographic poles
b. When North America and Europe are moved back to their predrift positions, their apparent wandering paths coincide
c. Evidence that North America and Europe were once joined and moved relative to the poles as part of the same continent
iii. Magnetic reversals and seafloor spreading
1. Over periods of hundreds of thousands of years, Earth’s magnetic field periodically reverses polarity
a. Lava solidifying during a period of reverse polarity will be magnetized with the polarity opposite that of volcanic rocks being formed today
i. Normal polarity—rocks with the same polarity as present magnetic field
ii. Reverse polarity—rocks with the opposite polarity of present magnetic field
b. Magnetic time scale established by radiometric dating techniques on magnetic polarity of hundreds of lava flows
2. Magnetic surveys of the ocean showed alternating stripes of high- and lowintensity magnetism that represent the polarity of the magnetism of Earth
a. Magma along a mid-ocean ridge “records” the current polarity of Earth
b. As the two slabs move away from the ridge, they build a pattern of normal and reverse magnetic stripes
3. Magnetic stripes exhibit a remarkable degree of symmetry in relation to the ridge axis, thus supporting seafloor spreading
10. How Is Plate Motion Measured?
a. Geologic measurement of plate motion
i. An average rate of plate motion can be calculated from the radiometric age of an oceanic crust sample and its distance from the ridge axis where it was generated
ii. Combine age data with paleomagnetism data to get maps of age of the seafloor
iii. Shows us that the rate of seafloor spreading in the Pacific basin must be more than three times greater than in the Atlantic
iv. Fracture zones are inactive extensions of transform faults, and therefore preserve a record of past directions of plate motion
b. Measuring plate motion from space
i. Data from Global Positioning System (GPS) establish the rate of movement of plates using repeated measurements over many years
ii. GPS devices have also been useful in establishing small-scale crustal movements such as those that occur along faults in regions known to be tectonically active
iii. GPS measurements have also confirmed small-scale crustal movements such as those along faults in tectonically active areas
11. What Drives Plate Motions?
a. Some type of convection, where hot mantle rocks rise and cold, dense oceanic lithosphere sinks, is the ultimate driver of plate tectonics
b. Forces that drive plate motion
i. Slab pull: subduction of cold, dense slabs of oceanic lithosphere is a major driving force of plate motion
ii. Ridge push: gravity-driven mechanism results from the elevated position of the oceanic ridge, which causes slabs of lithosphere to “slide” down the flanks of the ridge
iii. Ridge push appears to contribute far less to plate motions than slab pull
iv. Mantle drag resists plate motion when the asthenosphere is moving more slowly than the plate, or in the opposite direction
c. Models of plate-mantle convection
i. Convective flow is the underlying driving force for plate movement
ii. Mantle convection and plate tectonics are part of the same system
iii. Convective flow in the mantle is a major mechanism for transporting heat away from Earth’s interior
iv. Two models:
1. Whole-mantle convection (Plume Model)
a. Cold oceanic lithosphere sinks to great depths and stirs the entire mantle
b. Suggests that the ultimate burial ground for subducting slabs is the core-mantle boundary
c. Downward flow is balanced by buoyantly rising mantle plumes that transport hot material toward the surface
d. Two kinds of plumes: narrow tubes and giant upwellings
2. Layer cake model
a. Mantle has two zones of convection—a thin, dynamic layer in the upper mantle and a thick, larger, sluggish one located below
b. Downward convective flow is driven by the subduction of cold, dense oceanic lithosphere
c. These subducting slabs penetrate to depths of no more than 1000 kilometers (620 miles)
d. The lower mantle is sluggish and does not provide material to support volcanism at the surface
e. Very little mixing between these two layers is thought to occur
v. Geologists continue to debate the nature of convective flow of the mantle
LEARNING OBJECTIVES/FOCUS ON CONCEPTS
Each statement represents the primary learning objective for the corresponding major heading within the chapter. After completing the chapter, students should be able to:
2.1 Summarize the view that most geologists held prior to the 1960s regarding the geographic positions of the ocean basins and continents.
2.2 List and explain the evidence Wegener presented to support his continental drift hypothesis.
2.3 Summarize the two main objections to the continental drift hypothesis.
2.4 List the major differences between Earth’s lithosphere and its asthenosphere, and explain the importance of each in the plate tectonics theory.
2.5 Sketch and describe the movement along a divergent plate boundary that results in the formation of new oceanic lithosphere.
2.6 Compare and contrast the three types of convergent plate boundaries and name a location where each type can be found.
2.7 Describe the relative motion along a transform fault boundary and be able to locate several examples on a plate boundary map.
2.8 Explain why plates such as the African and Antarctic plates are increasing in size, while the Pacific plate is decreasing in size.
2.9 List and explain the evidence used to support the plate tectonics theory.
2.10 Describe two methods researchers use to measure relative plate motion.
2.11 Describe plate-mantle convection and explain two of the primary driving forces of plate motion.
TEACHING STRATEGIES
Muddiest Point: In the last 5 minutes of class, have students jot down the points that were most confusing from the day’s lecture, and what questions they still have. Or, provide a “self-guided” muddiest point exercise, using the Clicker PowerPoints and website questions for this chapter. Review the answers, and cover the unclear topics in a podcast to the class or at the beginning of the next lecture.
The following are fundamental ideas from this chapter that students have the most difficulty grasping and activities to help address these misconceptions and guide learning.
A. Movement of Plates
a. Students have many misconceptions about plate motion. These may include: only continents move, oceans are stationary, plate movement is imperceptible on a human timeframe, the size of Earth is gradually increasing over time because of seafloor spreading, plate tectonics started with the breakup of Pangea, and tectonic plates drift in oceans of melted magma just below the surface of Earth. As you discuss plate tectonics, integrate imagery, graphics, and animations to help students visualize the processes involved (see Teacher Resources in the following section)
b. Isostasy Animation http://www.geo.cornell.edu/hawaii/220/PRI/isostasy.html
i. This interactive animation allows students to visualize how continental and oceanic crust “float” on the mantle. In the menu along the bottom, enter a liquid density of 3.3 g/cm3, the average density of the asthenosphere—this will stay the same. Then, enter the thickness and density of oceanic crust (5 kilometers thick, density of 3.0 g/cm3). Record the height of the block above the liquid—you will have to subtract the block height from the block root value.
Do the same for continental crust (50 kilometers thick, density of 2.7 g/cm3). ii. Then, ask students: Which sits higher above the liquid surface? Which sits lower? Why? Use this as a lead-in to tectonics—if plates can move up and down (buoyancy) in the asthenosphere, might they also move back and forth? Why? This is plate tectonics—plates moving laterally across the asthenosphere.
c. Hot Spot Model Activity
i. (Supplies: metal pan, spray bottle of water, about one cup of sugar, a candle or tea light, lighter/matches). Spray a disposable metal pan with water, and then add a thin layer of sugar. Have one student hold the lit candle stationary beneath the pan of sugar. Have another student slowly move the pan in one direction over the candle. Students should see “islands” of molten sugar form on the surface as the pan (plate) moves over the candle (hotspot).
ii. (Supplies: blank overhead and overhead pens) One student is the “hotspot”
(pen); another is the “plate” (overhead). Ask the “plate” student to move the “plate” to the NW (like the Pacific plate) while the “hotspot” student holds the pen stationary on the overhead. Result is a linear chain created on the moving plate.
d. Tracking Tectonic Plates Activity http://serc.carleton.edu/NAGTWorkshops/intro/activities/28504.html
e. Subduction Zone Earthquake Activity http://serc.carleton.edu/introgeo/demonstrations/examples/subduction_zone_ear thquakes.html
f. Nannofossils Reveal Seafloor Spreading Truth Activity http://www.oceanleadership.org/wp-content/uploads/2009/08/Nannofossils.pdf g. You Try It: Plate Tectonics http://www.pbs.org/wgbh/aso/tryit/tectonics/shockwave.html
h. Sea-Floor Spreading Activity http://oceanexplorer.noaa.gov/edu/learning/player/lesson02/l2la2.htm
B. Characteristics of Plates and Boundaries
a. Students have difficulty understanding relationships between geologic processes and plate boundaries until they can clearly visualize and analyze their relationships.
b. Discovering Plate Boundaries Activity http://plateboundary.rice.edu/intro.html
c. A similar activity on plate boundaries using Google Earth: http://serc.carleton.edu/NAGTWorkshops/structure/SGT2012/activities/63925.html
d. NOAA Mid-Ocean Ridge Activity http://www.montereyinstitute.org/noaa/lesson02/l2la1.htm
e. NOAA Earthquakes and Plates Activity http://www.montereyinstitute.org/noaa/lesson01/l1la2.htm
C. Paleomagnetism
a. The ideas of paleomagnetism are often difficult for students to grasp. Again, visualizations are key here.
b. Magnetic Reversals Activity https://www.msu.edu/~tuckeys1/highschool/earth_science/magnetic_reversals.pdf
c. A Model of Seafloor Spreading Activity http://www.ucmp.berkeley.edu/fosrec/Metzger3.html or http://www.geosociety.org/educate/LessonPlans/SeaFloorSpreading.pdf TEACHER RESOURCES
Web Resources
• This Dynamic Earth http://pubs.usgs.gov/gip/dynamic/dynamic.html • Teaching Plate Tectonics With Illustrations http://geology.com/nsta/
• Continents on the Move www.pbs.org/wgbh/nova/ice/continents/
• GPS—Measuring Plate Motions http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/14/1.GPS_Background.pdf
Animations and Interactive Maps
• This Dynamic Planet Interactive Map http://nhb-arcims.si.edu/ThisDynamicPlanet/index.html
• Plate Tectonics Animations http://www.ucmp.berkeley.edu/geology/tectonics.html
• Exploring Our Interactive Planet Interactive Mapping Tool http://www.dpc.ucar.edu/VoyagerJr/intro.html
• Plate Motion Simulations http://sepuplhs.org/middle/iaes/students/simulations/sepup_plate_motion.html
• Imagery, Maps, Movies, and References on Plate Tectonics http://www.ig.utexas.edu/research/projects/plates/
