Project I

 





Exercise 9 : Plate Tectonics

Questions

  1. If the Atlantic Ocean is widening at a rate of 3 cm per year, how far (in kilometers) will it spread in a million years? In 200 million years?

  2. The Plate Motion Calculator will let you make some calculations that lead to a better understanding of present day plate motion. Use the following data and think about the implications. [For the following two problems use the Absolute Motion calculator.]

    1. Obtain the longitude and latitude of UH (to the nearest degree will be sufficient). What is the velocity of the plate at this locality? Make sure you select the proper plate and read the directions for entering latitude and longitude. The direction East would be at 90 degrees, South at 180 degrees and West at 270 degrees; use this reference in interpreting the calculated "direction". Assuming that the velocity will be constant, how long will it take your location to move 2,000 kilometers (assuming that the direction of movement remains constant)?

    2. Santiago Chile is located at 30 degrees S latitude and 70 degrees W longitude. What is the velocity of the South American Plate at this point? The Juan Fernandez island on the Nazca Plate is located at 30 degrees S latitude and 80 degrees W longitude. What is its velocity?

    3. The South American Plate and the Nazca Plate are converging. Will the South American Plate "overtake" the Nazca and "sit" on top of the East Pacific Rise? Or, will the distance between the South American Plate and the Nazca Plate increase?

    4. Set up a problem involving the State of Washington (on the North American plate) and the Juan de Fuca plate. Use an atlas to select a constant latitude for both plates and vary the longitude accordingly. Describe what may eventually happen to these two plates.

  3. The faster the spreading rate, the wider the magnetic anomalies. Hot spots (such as the one in the asthenosphere beneath Hawaii) may provide a fixed reference point which can be used to determine absolute motion of the Pacific plate. Return to the image showing the distribution of earthquake epicenters and plate boundaries (the enlarged version). Locate Hawaii and note that the earthquakes are concentrated near the southeastern end of the chain. Ages of volcanism increase to the northwest along the chain. The hot spot is in the asthenosphere and the islands develop in the overlying lithosphere. As the Pacific plate moves to the northwest new lithosphere "sits" on top of the hot spot and a new episode of volcanism is initiated. Follow the chain to the northwest where it becomes the northward trending Emperor seamounts. The "bend" is some 40 million years old. What do you think happened 40 million years ago?

  4. Hot spots can occur beneath continents and it is proposed that the Yellowstone area in Wyoming sits on top of a hot spot. If the North American plate is moving to the West, where will the volcanism and thermal affects associated with the hot spot be in a million years?

  5. There are two types of shorelines:

    • those that coincide with a plate margin (an active margin) and
    • those that don't (a passive margin)

    Look at the map of plate boundaries. Describe the southern California shoreline ... the east coast of North America .... the west coast of South America. Comment on potential differences between these two types of coast lines.

There are a number of organizations which focus on Earthquake Hazards and Preparedness .