topo features of alpine glaciers lab - soinc.org

Copyright: Gary R. Vorwald, Paul J. Gelinas jHS, Setuaket, NY 2013 (May be used for educational purposes; please credit author)

Name: _______________________________ Period: _____ Date: ____________________ LAB: Topographic Features and Advance/Retreat of Alpine Glaciers Background: The map in this lab shows three glaciers in the Juneau Ice Field in Alaska. It shows the Taku Glacier, one of the largest glaciers in the ice field as well as the smaller Norris, and Hole-in-the-Wall Glaciers. The topographic map includes land contours, glacial contours, and the positions of the margin of each glacier at different times since 1890. Glaciers gain and lose snow and ice each year. The amount of snow and ice added to a glacier is called accumulation and amount lost due to melting is called ablation. This relationship is called the glacial budget. In this lab, you are going to analyze the topographic map to determine glacial features, such as U-shaped valleys, sharp mountain peaks, and moraines, as well as the dimensions of the glaciers. The map was made in 1980, and includes positions of the terminus (ice margin) during different times since 1890. Where are the glaciers now, in 2013? By determining the rate of advance or retreat, we can predict where the glacier will be in the future. Of course, this may depend on the rate not changing over time. Make a prediction as to where you think the glaciers are now, and then write a conclusion after you analyze your data and review Google map images of the Taku Glacier Region. Hypothesis: ____________________________________________________________ PART 1: Topographic Map Analysis Directions: Answer the following questions based upon the map of Alpine Glaciers in the Juneau Icefield, Alaska. 1. Lightly shade the areas of ice, land and water on the map.

Lowland = brown Highland - Green Water = blue Glaciers = white


2. What is the contour interval of the land on this map? _________________________ 3. a. What is the highest elevation on the map? ________________

b. Where is this located? ________________________________________________

4. What is the approximate elevation of the Taku River? _______________ 5. What is the contour interval of the glacier on this map? _______________________ 6. Using the scale, measure the north-south distance covered by the map in miles and kilometers. _________________ mi _________________km 7. Measure the east-west distance covered by the map in miles and kilometers. _________________ mi ________________ km 8. What is the approximate latitude and longitude of the Taku Glacier along it’s 1980 front at point X?

(Your answer should be stated to the nearest degree and minute)

_____________________________________________________ 9. State the width of the Taku Glacier at the terminus (end). _____________________ 10. State the width of the Taku glacier at the 1000 ft. contour. _____________________ 11. Calculate the gradient of the Taku Glacier from point Y along the 1000ft contour to point Z (at the

Taku River, elevation 0 ft.). (Rate should be expressed in feet per mile)

a. State the Equation for Gradient

Gradient = _________________________

b. Substitute Values into the Equation

Gradient = _________________________

c. Solve the equation and state your Final Answer

Gradient = _________________________


Draw a topographic profile across the Taku Glacier, from point A to point B. Plot each elevation value using a point and then connect the points with a smooth line. Draw a dashed line to show your interpretation of the depth of the glacier and Taku River.

12. Based on your profile, how thick is the Taku Glacier? ____________________

13. What is the name of the glacial landform at A? _____________________

14. Describe or give the name of the glacial landform directly east of the 1000 ft contour on

the Taku Glacier? ________________________________________________________

15. When the Taku Glacier completely melts, what shape will the valley be? ____________

16. Describe the topography of this region. _____________________________________ ________________________________________________________________________

17. The dark lines on the glacier indicate the position of the glaciers terminus (glaciers front) at various dates in the past. Use this information to state if the glaciers appear to be advancing or retreating.

Taku Glacier = ________________________ Norris Glacier = ______________________ Hole-in-the-Wall Glacier = __________________________


PART 2: Prediction of Position of Glaciers 1. Calculate the rate of movement of the Taku Glacier for the following periods of time: 1890-1929; 1929-1948; 1948 – 1980. Use the kilometer scale. Calculate rate in both km/yr and meters/year. 1 km = 1000 meters.

a. 1890 – 1929

Distance (km)

Distance (meters)

Time (years)

Rate (km/yr)

Rate (m/yr)

b. 1929 – 1948

Distance (km)

Distance (meters)

Time (years)

Rate (km/yr)

Rate (m/yr)

c. 1948 – 1980

Distance (km)

Distance (meters)

Time (years)

Rate (km/yr)

Rate (m/yr)

2. Based on your calculations, describe your observations of the rate from 1890 – 1980. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________


3. Use your calculations of rate to predict where the Taku Glacier is now (2013). You decide which interval to use.

Convert the rate formula to solve for the predicted distance. Rate = Distance/Time Distance =

Rate (km/yr)

Time (years)

Predicted Distance (km)

4. Indicate on the map where you think the Taku Glacier is today, based on your calculations. 5. Predict the location of the Norris Glacier in 2010. Use a red marker or pencil.

Rate (km/yr)

Time (years)

Predicted Distance (km)

Indicate the location of the Norris Glacier on the map. Use a red marker or pencil.

Distance (km)

Distance (meters)

Time (years)

Rate (km/yr)

Rate (m/yr)


Discussion Questions:

1. What is the length, width, and approximate thickness of an Alpine (Valley) Glacier? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

2. What are some topographic characteristics of a region that has been affected by alpine glaciers? Describe some landforms observed on your map of the Taku Glacier. Include the shape of the valley being carved by the glaciers.

___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

3. What conditions cause a glacier to advance or retreat? (Relate to annual snowfall accumulation and melting/ablation)

___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

4. The Taku Glacier currently appears have been in a state of Dynamic Equilibrium since 1980 . Explain what the relationship between accumulation and melting is and describe where the glacier is now compared to the river.

___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________


___________________________________________________________________ Conclusion: Write a conclusion about what you learned about glaciers from this lab. Include information about your rate calculations and how you can predict future positions of a glacier. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Evaluation: ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

topo features of alpine glaciers lab - soinc.org

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