**Interactive Crevasse** **and Snow Mound** **Tracking**

***[Task Overview]{.underline}***

**A** **crevasse** **is a**
[**fracture**](http://en.wikipedia.org/wiki/Fracture) **in a**
[**glacier**](http://en.wikipedia.org/wiki/Glacier) **caused by
enormous** [**tensile
stresses**](http://en.wikipedia.org/wiki/Tensile_stress) **at or near
the glacier\'s surface.** **A snow mound is simply an accumulation of
snow forming a hill-like structure.** **Accelerations in glacier speed
cause extension and can initiate a crevasse. Crevasses often have
vertical or near-vertical walls** **that** **sometimes expose layers
that represent the glacier\'s**
**[stratigraphy](http://en.wikipedia.org/wiki/Stratigraphy).**
**Tracking crevasse** **and snow mound** **movement is an excellent way
for scientists to determine actually how far a glacier has moved within
a certain span of time. Crevasses also pose a danger to scientists in
the field in that they can be hidden from plain sight by a recent
snowfall or an unstable snow bridge.**

***[Standards]{.underline}***

***National Science Education Standards addressed:***

-   **Science as Inquiry-Content Standard A**

-   **Energy in the Earth System-Content Standard D**

-   **History and Nature of Science-Content Standard G**

***Benchmarks for Science Literacy addressed:***

-   **The Nature of Science**

    -   **1~B~-Scientific Inquiry**

    -   **1~C~-The Scientific Enterprise**

-   **The Physical Setting**

    -   **4~B~-The Earth**

    -   **4~C~-Processes that Shape the Earth**

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-   **Common Themes**

    -   **11~A~-Systems**

***[Objectives]{.underline}***

A.  **Students will determine the distance several crevasses have
    traveled over a 6.94** **year period.**

B.  **Students will identify the crevasses on a** **set** **of Landsat
    images along the** **Bindschadler Ice Stream in West Antarctica.**

C.  **Students will identify and track several snow mounds and compare
    their rates to the crevasses.**

***[Materials]{.underline}***

**Landsat images of crevasses** **and snow mounds** **from 1985 and
1991**

**Internet-ready computer with JAVA enabled browser.**

***[Procedure]{.underline}***

**Part I: Crevasse Tracking**

1.  **You will be estimating the distances crevasses have moved from**
    **January 02,** **1985 to** **December 12,** **1991.**

2.  **Locate** **Crevasse A on the 1985 image. This is labeled.**

3.  **Locate the new location of Crevasse A on the 1991 image. This is
    not labeled, it is your job to find it.**

4.  **Using the 2 km scale provided, estimate how far you think the
    crevasse has moved over the 6.94-year** **time period.** **Enter
    your estimate into Table 1a.**

5.  **Convert your estimate in kilometers to meters.** **Entire your
    conversion into Table 1a.**

6.  **Determine how** **far the crevasse has traveled in meters/year.**
    **Enter your calculation into Table 1a**

7.  **Repeat for all** **Crevasses B-E.**

8.  **Once you have all your estimated measurements entered into**
    **Table 1a, go to**
    [**http://lima.gsfc.nasa.gov/mysteries/q1/index.php?page=Crevassed**](http://lima.gsfc.nasa.gov/mysteries/q1/index.php?page=Crevassed)

9.  **Using the online applet tool, measure the distance each crevasse
    has traveled.** **Enter this information into Table 1b.**

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

**Enter how close your estimates were to the computer-generated model.**
**Enter this information into Table 1c.**

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![](media/image3.png){width="2.975in"
height="2.975in"}![](media/image4.png){width="2.95625in"
height="2.98125in"}

***Table 1a***

  -------------- ------------------------- --------------- -------------------
  **Crevasse**   **Estimated Distance      **Conversion to **Distance Traveled
                 Traveled (km)**           meters**        (m/year)**

                                                           

  **Crevasse A**                                           

  **Crevasse B**                                           

  **Crevasse C**                                           

  **Crevasse D**                                           

  **Crevasse E**                                           
  -------------- ------------------------- --------------- -------------------

***Table 1b***

  --------------------- -------------------------------------------------
  **Crevasse**          **Computer-Generated Distance/year (m)**

                        

  **Crevasse A**        

  **Crevasse B**        

  **Crevasse C**        

  **Crevasse D**        

  **Crevasse E**        
  --------------------- -------------------------------------------------

***Table 1c***

  -------------- ------------------------------------------------------------
  **Crevasse**   **Difference between Your Measurement and Computer-Generated
                 Measurement (m/year)**

                 

  **Crevasse A** 

  **Crevasse B** 

  **Crevasse C** 

  **Crevasse D** 

  **Crevasse E** 
  -------------- ------------------------------------------------------------

**Part II: Snow** **Mound Tracking**

1.  **You will be now be estimating the distances snow mounds have moved
    from** **January 02,** **1985 to** **December 12,** **1991.**

2.  **Locate Snow Mound 1 on 1985 image. This is labeled.**

3.  **Locate the new location of Snow Mound** **1 on the 1991 image.
    This is not labeled, it is your job to find it.**

4.  **Using the 2 km scale provided, estimate how far you think the**
    **snow mound** **has moved over the 6.94-year time period.** **Enter
    your estimate into Table 2a.**

5.  **Convert your estimate in kilometers to meters.**

6.  **Determine how far the crevasse has traveled in meters/year.**

7.  **Enter all your information in** **Tables 2a, 2b, and 2c**
    **below.**

8.  **Repeat for Snow Mounds 2 and 3.**

9.  **Once you have all your estimated measurements entered into the
    table, go to**
    [**http://lima.gsfc.nasa.gov/mysteries/q1/index.php?page=Crevassed**](http://lima.gsfc.nasa.gov/mysteries/q1/index.php?page=Crevassed)

10. **Using the online applet tool, measure the distance each** **snow
    mound** **has traveled.**

11. **Enter the computer-generated values in the table section below.**

12. **Enter how close your estimates were to the computer-generated
    model.**

**Table 2a**

  ------------ ------------------------ --------------- ------------------
  **Snow       **Estimated Distance     **Conversion to **Distance
  Mound**      Traveled (km)**          meters**        Traveled
                                                        (m/year)**

                                                        

  **Snow Mound                                          
  1**                                                   

  **Snow Mound                                          
  2**                                                   

  **Snow Mound                                          
  3**                                                   
  ------------ ------------------------ --------------- ------------------

**Table 2b**

  ---------------------- ------------------------------------------------
  **Snow Mound**         **Computer-Generated Distance/year (m)**

                         

  **Snow Mound 1**       

  **Snow Mound 2**       

  **Snow Mound 3**       
  ---------------------- ------------------------------------------------

**Table 2c**

  ----------- -----------------------------------------------------------
  **Snow      **Difference between Your Measurement and
  Mound**     Computer-Generated Measurement (m/year)**

              

  **Snow      
  Mound 1**   

  **Snow      
  Mound 2**   

  **Snow      
  Mound 3**   
  ----------- -----------------------------------------------------------

***[Assessment]{.underline}***

1.  **Were your estimates accurate? If not, what do you think the reason
    was for the inaccuracy?**

2.  **Why is knowing how crevasses move an important** **variable**
    **for scientists and research in Antarctica to know?**

3.  **Where is the ice moving the fastest in this image? The slowest?**

**Did the depth and volume change at each timed interval?**

4.  **How can we translate the** **crevasse tracking** **you have seen
    in this activity to larger scale global changes?**