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Section 2
Earth's Moving Lithospheric Plates

In this section you will find materials that support the implementation of EarthComm: Florida, Section 2: Earth's Moving Lithospheric Plates.


Learning Through Technology

To learn more about the relative motions of the plates, complete the following:

Data from a Computer Model

  1. Computer models that use geo-spatial data can be used to show changes in the location of your community. To use such a model, you will need to know the latitude and longitude of your school (or another familiar place).  Latitude and longitude are used to identify a position on the Earth’s surface. Latitude is a measure of location in degrees, minutes, and seconds north or south of the equator. Longitude is a measure of location in degrees, minutes, and seconds east or west of the Prime Meridian, which passes through Greenwich, England. 

    You can use Google Earth to find the latitude and longitude of your school (or another familiar place).   After you open Google Earth, search for your specific location using the “Fly To” tab. Enter the location address in the input box and click on the “Search” button. Google Earth will zoom into your location.  Click on the “Add Placemark” icon to retrieve the latitude and longitude of the location. 

    google earth

    Alternatively, you can use your local topographic map. Latitude it is found on the left or right side of the map. Longitude is found on the top or bottom of the map.

    1. pencil Record the latitude and longitude of the position you chose in degrees, minutes, and seconds. (These “minutes” and “seconds” are not the same as the familiar minutes and seconds of time! They describe positions on a circular arc.)

    2. pencil Convert the latitude and longitude values to a decimal format. Use the following example to help you.

    Example:

    • 42° (degrees) 40' (minutes) 30" (seconds) north latitude
    • Each minute has 60"
    • 30" divided by 60" equals 0.5'
    • This gives a latitude of 42° 40.5' north
    • Each degree has 60'
    • 40.5' divided by 60' equals 0.675°
    • The latitude in decimal format is 42.675° north
  2. Examine the following map showing lithospheric plates.

    world map

    World map of major lithospheric plates. Arrows show the relative motions of the plates relative to the African Plate, which happens to be moving slowest relative to the Earth’s axis of rotation.
    1. pencil Identify the location of your community.
    2. pencil In your notebook, record the name of the plate your community lies within. Record the name of a plate next to your community.

  3. Visit the Relative Plate Motion (RPM) Calculator web site at: http://sps.unavco.org/crustal_motion/dxdt/nnrcalc/
    The RPM calculator determines how fast your plate is moving relative to another plate that is assumed to be “fixed” (non-moving). At the web site, enter the following information:

    • The latitude and longitude of your community (decimal format).
    • The name of the plate on which your community is located.
    • The name of the “fixed” reference plate adjacent to your plate. Use the African Plate as the reference plate.

    Once you have entered the data, run the model. Print the results. (Examine the following sample printout for the location of station WES2.) Record the following information in your notebook:
    1. pencil The rate of movement of the plate on which your community is located (in centimeters per year).
    2. pencil Its direction of motion. (Note that direction is given in degrees, starting from 0°, clockwise from north. For example, 90° is directly east, 180° is directly south and 270° is directly west.)
    3. pencil In your own words, describe the motion of your plate over time.
    4. pencil How do the results from the computer model compare to those obtained from GPS data?
    5. pencil What data does GPS provide that the plate motion calculator does not?

    Sample Printout for WES2
    NUVEL-1A Calculation Results
    Calculation results are as follows:

    Relatively fixed plate = Africa
    Relatively moving plate = North America
    Latitude of Euler pole = 78.8 degree
    Longitude of Euler pole = 38.3 degree
    Angular velocity = 0.24 degree/million years
    Latitude inputted = 42.364799 degree
    Longitude inputted = -71.293503 degree
    Velocity = 2.11 cm
    Direction = 283.39 degree

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Inquiring Further

  1. To learn more about how GPS works, visit the following web sites:

    GPS: A New Constellation, Smithsonian National Air and Space Museum
    Explores scientific methods before and after the advent of GPS, as well as a review of how GPS works and its applications. 

    Understanding Plate Motions, USGS
    Reviews the basics of plate motions and introduces the science of geodesy and using GPS to track current plate movements. Includes an image of a GPS satellite.

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Resources

To learn more about this topic, visit the following web sites:

The Interior Structure of the Earth

"The Interior of the Earth" by E.C. Roberston, USGS
Information about the composition of the crust, the mantle, and the core, and how each was "discovered" and studied.

Measuring Plate Motions with GPS

GPS: A New Constellation, Smithsonian National Air and Space Museum
Explores scientific methods before and after the advent of GPS, as well as a review of how GPS works and its applications. 

Understanding Plate Motions, USGS
Reviews the basics of plate motions and introduces the science of geodesy and using GPS to track current plate movements. Includes an image of a GPS satellite.

Tectonic Plate Motion, Space Geodesy, NASA
Describes the results of over 15 years of laser tracking data acquired by a network of globally distributed satellite laser ranging sites.

Plate Motion Calculator, UNAVCO
Calculate tectonic plate motion at any location on Earth using one or more plate motion models.

Sea-floor Spreading

Plate Tectonic Setting, USGS Cascades Volcano Observatory
Reviews the basics of plate tectonics including taking a look at sea-floor spreading. Includes several maps which highlight the "ring."

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