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Introduction to Plate Tectonics
This unit introduces Wegner's hypothesis about continental drift, Hess' theory of seafloor spreading, and the modern comprehensive theory of plate tectonics.

Workshop Presentations

The presentation about plate tectonics is divided into 3 separate discussions: Continental Drift, Seafloor Spreading and Plate Tectonics. This approach is meant to highlight the historical development of the theory of plate tectonics. The development of the theory is an excellent example of the cumulative nature of science and the scientifc process.

Continental Drift this presentation reviews Wegner's original hypothesis about the apparent movement of the continents.

PowerPoint Click to download the MS Powerpoint file (70 Mbytes)

PDF Click to view or download the presentation in PDF (1.9 Mbytes)

HTML Click to view the presentation in html format.

Online Lecture. Click here to view a streaming lecture about the Wegner's eveidence for Continental Drift. (~11 minutes).

This animation shows a reconstruction of the movement of the continents for the last 180 million years. This and other animations are available from the UCSB Educational Multimedia Visualization Center of the Department of Earth Science. This animation is available by clicking here.

Seafloor Spreading this presentation reviews the major features of the seafloor and Harold Hess' original theory of seafloor spreading.

PowerPoint Click to download the MS Powerpoint file (34 Mbytes)

PDF Click to view or download the presentation in PDF (2.1 Mbytes)

HTML Click to view the presentation in html format.

Online Lecture. Click here to view a streaming lecture discussing the rock cycle and igneous rocks. (~19 minutes).

This animation depicts sea floor spreading on three spreading centers that are connected by transform faults. The inset in the amination shows magnetic polarity reversals and the formation of seafloor magnetic stripes. This and other animations are available from the UCSB Educational Multimedia Visualization Center of the Department of Earth Science. This animation is available by clicking here.

Plate Tectonics this presentation reviews the modern theory of plate tectonics, plate margins and the occurrence of volcanism and earthquakes.

PowerPoint Click to download the MS Powerpoint file (146 Mbytes)

PDF Click to view or download the presentation in PDF (5 Mbytes)

HTML Click to view the presentation in html format.

Online Lecture. Click here to view a streaming lecture discussing the rock cycle and igneous rocks. (~42 minutes).

This animation shows subduction of oceanic crust under continental crust at a convergent margin. As the plate is subducted into the mantle, water in the slab is released and moves upward by buoyancy. The influx of water into the upper mantle lowers the melting point of rocks resulting in the formation of basaltic magma. As the magma rises buoyantly, its composition changes from basalt to andesite by a variety of processes. Hence, a line of volcanoes forms on the overriding plate that are parallel to the deep ocean trench. This and other animations are available from the UCSB Educational Multimedia Visualization Center of the Department of Earth Science. This animation is available by clicking here.

Classroom Activities

Wegner's Puzzle. Click to download a zipped folder of documents for this classic activity developed by the U.S. Geological Survey. This is an excellent starting activity for a unit on plate tectonics. In addition, the activity can demonstrates the fit of the continents to form Pangea and may be used as an introductory phenomenon. This activity permits students to use graphical displays (e.g., maps) to identify temporal and spatial relationships. (1.9 Mbytes). Zip Folder

Modeling Seafloor Spreading. Click to download this activity where students model seafloor spreading and the formation of magnetic "stripes" that provide primary evidence for the theory of plate tectonics. This activity permits students to use a model to test ideas about a phenomenaon at an unobservable scale (i.e., to understand the nature of the seafloor's magnetic stripes). In addition, it permits students to construct an explaation using the model.

Where Do Earthquakes and Volcanoes Occur? In this activity, students work in groups of four to plot the locations of 20 active volcanoes and 20 major earthquakes. Students compare their results with a plate tectonic map to investigate the relationship between plate boundaries and the locations of earthquakes and volcanoes. This activity permits students to use graphical displays (e.g., maps) of large data sets (earthquake and volcano locations) to identify spatial relationships with tectonic margins.

Where Did Pinnacles National Park Come From? In this activity, students examine movement of the Neenach volcanic rocks in Pinnacles National Park northward along the San Andreas fault. This activity permits students to apply mathematical concepts (e.g. rate) to a scientific question about the rate of motion along the San Andreas fault and predicting future movement.

How Fast is the Pacific Plate Moving? PDF Word Document In this activity, students examine geochronological data for lava flows that form the Hawaiian Islands and use that data and the distances of the islands from the Hawaiian mantle hotspot to detemine the rate that the Pacific Plate is moving over. This activity permits students to apply mathematical concepts (e.g. rate) to a scientific question about the rate of motion of the Pacific plate over the Hawaiian hotspot. Teacher Key

Online Video and Media Resources

This Dynamic Planet Interactive Map This is a very cool interactive map that shows the locations of volcanoes, earthquakes, plate boundaries and impact craters. This website has a lot of graphic data and requires a fast internet connection (be patient while loading). Smithsonian Institution.

This Dynamic Planet The USGS has produced a spectacular printed map. This website is the companion to the printed map and includes links to downloadable maps. USGS

This Dynamic Earth: The Story of Plate Tectonics This is an online publication that provides detailed information about plate tectonics. USGS

Educational Multimedia Visualization Center Animations (Atwater, UCSB)

Teachers on the Leading Edge There are many resources and activities developed by this professional development program for middle school science teachers.

Plate Tectonics: An Introduction This video introduces plate tectonics and how the Earth's surface has changed over geologic time. Click here to access the source website including additional resources. WGBH Educational Foundation

Plate Tectonics: The Scientist Behind the Theory This video introduces the three major types off plate boundaries. Click here to access the source website including additional resources. WGBH Educational Foundation

Plate Tectonics: Further Evidence This video introduces the three major types off plate boundaries.Click here to access the source website including additional resources. WGBH Educational Foundation

Plate Tectonics: Lake Mead, Nevada This short video examines the Lake Mead area of the Basin and Range province where extension of the North American crust is occurring. Click here to access the source website including additional resources. WGBH Educational Foundation

Continental Divide: The Breakup of Pangaea Interactive animation shows the breakup of Pangeae with evidence from rocks and fossils. WGBH Educational Foundation

Plate Tectonics: The Hawaiian Archipelago This video introduces the formation of Hawai'i from a mantle hot spot. Click here to access the source website including additional resources. WGBH Educational Foundation

Earthquake! When Plates Collide (WGBH Educational Foundation). Click here to access the source website including additional resources.

Continental Divide: The Breakup of Pangaea (Interactive animation, WGBH Educational Foundation).

Useful Websites

USGS Earthquake Hazards Program earthquake.usgs.gov/ This USGS site is the main entry point for information on earthquakes including realtime earthquake maps.

Realtime Global Earthquake Map http://earthquake.usgs.gov/earthquakes/map/ This is an interactive map showing the occurrence of earthquakes. Please note that you can zoom into any location for more detail and change the map options to display different magnitude earthquakes.

United States Geological Survey (USGS) www.usgs.gov/ The USGS is a federal agency within the U.S. Department of the Interior and has primary responsibility for geological (hazards, resources, etc.) and environmental issues of national and regional importance.

The Educational Multimedia Visualization Center emvc.geol.ucsb.edu/ This website contains terrific animations illustrating tectonic plate motion. UCSB

Teachers on the Leading Edge orgs.up.edu/totle/ There are many resources and activities developed by this professional development program for middle school science teachers.

NGSS Disciplinary Core Ideas

Grade 2
ESS1.C: The History of Planet Earth. Some events happen very quickly; others occur very slowly, over a time period much longer than one can observe.

Grade 4
ESS1.C: The History of Planet Earth. Local, regional, and global patterns of rock formations reveal changes over time due to earh forces, such as earthquakes. The presence and location of certain fossil types indicate the order in which rock layers were formed.

ESS2.B: Plate Tectonics and Large-Scale System Interactions. The locations of mountain ranges, deep ocean trenches, ocean floor structures, earthquakes, and volcanoes occur in patterns. Most earthquakes and volcanoes occur in bands that are often along boundaries between continents and oceans. Major mountain chains form inside continents or near their edges. Maps can help locate the different land and water features areas of the Earth.

ESS3.B: Nature Hazards. A variety of hazards result from natural processes (e.g., earthquakes, tsunamis, volcanic eruptions). Humans cannot eliminate the hazards but can take steps to reduce their impacts.

Middle School
ESS2.B: Plate Tectonics and Large-Scale System Interactions Maps of ancient land and water patterns, based on investigations of rocks and fossils, make clear how Earth's plates have moved great distances, collided, and spread apart.

ESS3.B: Natural Hazards Mapping the history of natural hazards in a region, combined with an understanding of related geologic forces can help forecast the locations and likelhoods of future events.

High School
ESS3.B: Natural Hazards Natural hazards and other geologic events have shpated the course of human history; [they] have significantly altered the sizes of human populations and have driven human migrations.

Common Scientific Misconceptions

Crust and Lithosphere (or plates) are synonymous terms

Asthenosphere is liquid (students are only familiar with liquid convection, not solid convection, many secondary education earth science films also specifically refer to a molten internal layer).

Lower Mantle is liquid (for reasons similar to above).

Earth's core is hollow, or that large hollow spaces occur deep within Earth (a relict of older cosmology and a mainstay of popular literature and Hollywood movies).

Only continents move (Wegener's original concept, along with the common use of 'Continental Drift' term in general texts, secondary education earth science films, etc.)

Most crust motions (especially those associated with processes of mountain building or deep sea trench formation) are due to vertical motions, not lateral (terms like 'mountain uplift' and earth science textbook terminology, as well as relict idea from old cosmologies).

Divergent ocean ridges are due to vertical uplift or convergence, rather than divergence (In students' experience, buckling is usually due to convergence or uplift, not heat/density differences, so illustrations of ridges do not readily fit with a pulling apart motion).

Present oceans only began as Pangea broke apart - tied to general idea that Pangea was the original continent at the Earth's start (few educational earth science films mention what came before Pangea & emphasis on Atlantic spreading leads to Pacific being overlooked).

Plate movement is imperceptible on a human timeframe (common use of fingernail growth analogy is only true for slowest plates and underestimates importance of motion).

Plate motion is rapid enough that continent collision can cause financial and political chaos, while rifting can divide families or separate a species from its food source.

Oceans are responsible for oceanic crust (rather than being closer to other way round).

Continental 'shelves' are similar to shelves in homes, extend out over edge of continent and can break and collapse to form tsunamis (so Boxing Day tsunami was due to shelf collapse)

The edge of a continent is the same thing as a plate boundary.

Over time there has been no significant change in ratio of oceanic to continental areas (idea of stasis is a common misconception, but this was also part of Lyell's original concept).

Apart from differences due to changes in ice volume, sea level has remained relatively constant through time (recognition of impact of plate speed on sea level not even recognized by geologists until relatively recently).

A plate boundary type is the same thing as a plate. For example, a plate has to be divergent or convergent.

 

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