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EXERCISE

  1. What type of moraine does each of the following letters identify?

A: Lateral moraine: it's a ridge of unconsolidated material along the valley wall.

B: Medial moraine: it's a ridge of unconsolidated material on top of and in the middle of a glacier; two lateral moraines join to form it.

C: Medial moraine (two medial moraines that have merged)

D: Lateral moraine

  1. What type of glacier does the letter Z identify?

    Valley Glacier: ice flow is restricted by the pre-existing topography.

  2. How would this glacier be symbolized on a topographic map?

    Blue contour lines on a white background with a dashed blue line defining the edges of the glacier.
Photo: glacial landscape
Photo: D. Becker. 2008. USGS Multimedia Gallery, photo BeckerDSC_4800.jpg. <http://gallery.usgs.gov/> Accessed July 2010.

  1. What type of glacial landform does the photo to the right show an excellent example of?

The photo shows a glacial trough or a U-shaped valley.

 

Photo: glacial landscape
Photo: S. Hillebrand. 2008. U.S. Fish and Wildlife Service National Digital Library, image Volume1\8DB2BF2D-D50E-A44B-B4F6E5BD6227D4E6.jpg. <http://www.fws.gov/digitalmedia> Accessed June 2010.

  1. What type of glacier features is the arrow pointing to?

    Crevasses; cracks in the surficial ice.

  2. What could cause these features to form?

    Ice can flow only so fast, and when the slope or conditions are right for ice to flow faster than the rate at which ice can deform, crevasses develop. There is probably a small drop-off or short steep segment underlying the ice at this location causing the crevasses to form.

 

 

Photo: glacial landscape
Photo: S. Hillebrand. 2008. U.S. Fish and Wildlife Service National Digital Library, image Volume1\ED5BDC7D-65BF-03E7-2FCE9EE8E0179796.jpg. <http://www.fws.gov/digitalmedia> Accessed June 2010.

  1. What type of moraine are the red arrows pointing to? Justify your answer.

    This is an end moraine. Ice is visible behind the moraine (to the left of it) and the moraine has a classic curved shape as a result of faster ice flow in the center than along the margins of the glacier. A lot of sediment is visible beyond the moraine. It is not possible to determine whether this is a terminal moraine or a recessional moraine; you would need information on the landscape downslope from this location to determine whether this end moraine was a terminal or a recessional moraine.



  2. How would this moraine be symbolized on a topographic map?

    Brown speckles.

 

 

Photo: glacial landscape
Photo: R. March. 2002. USGS Multimedia Gallery, photo DCP_0641.jpg. <http://gallery.usgs.gov/> Accessed July 2010.

  1. How can you distinguish bedrock from glacial ice from unconsolidated moraine deposits on this topographic map?

    Areas of bedrock are symbolized as brown contour lines with a white background. Glacial ice is symbolized as blue contour lines with a white background. Unconsolidated moraine deposits are symbolized as brown speckles.


  2. What glacial landform is the letter A pointing to? Justify your answer.

    Lateral moraines; these moraines are located along the margins of the glacier adjacent to the valley walls.



  3. What type of glacial landform is the letter B pointing to? Justify your answer.

    Medial moraine; these brown speckles run down the center of the glacier. The medial moraine starts where two lateral moraines join.


  4. Describe the general appearance of the landform identified by the letter B; what would this landform look like if you could see it in person?

    The medial moraine would appear as a ridge of rocks and other unconsolidated debris sitting on top of the glacier with ice on either side of the ridge.


  5. How does the shape of the contour lines help define what the landform represented by letter B looks like?

    As the contour lines cross the moraine ridge, the lines form a small "v" or "u" shape with the bottom of the "v" or "u" pointing toward lower elevations. When contour lines cross ridges, they form v's or u's (depending on the width of the ridge) that bend downhill. Thus, the contour lines help us visualize what the moraine would look like in person.


  6. What type of landform do the letter C's represent?

    The C's are sitting on brown speckles located beyond the margin of the glacier so they probably represent an end moraine. You can't tell whether the end moraine is a terminal or a recessional moraine without seeing more of the landscape farther downhill.
Topographic Map: Mt. Rainier East

  1. What type of landform is the letter A representing?

    Cirque headwall; this is solid bedrock (not unconcolidated material) that is nearly vertical.


  2. What type of glacier is glacier B?

    Cirque glacier.


  3. What type of landform is indicated by the letter C? Justify your answer.

    End moraine. This feature is composed of unconsolidated material, not solid bedrock, so it's a moraine. There is ice behind the moraine separating the moraine from the headwall, so this is most likely an end moraine not a lateral moraine. Without seeing more of the landscape it is not possible to determine whether the end moraine is a terminal or a recessional moraine.

 

Photo: glacial landscape
Photo: T.W. Stanton. 1911. USGS Photographic Library, photo stw00711. <http://libraryphoto.cr.usgs.gov/> Accessed July 2010.

  1. What type of glacier landform is identified by the letter A?

    An icefall; you can see the slope here is steeper than elsewhere.

  2. What type of glacier landform is identified by the letter B?

    Ogives.

  3. Approximately how many years of glacial flow is visible based on the features identified by the letter B? Explain.

    Approximately 20 years. The ogives form ridges and swales; the ridges represent winter ice and the swales represent summer ice. The number of ridges should approximately equal the number of years of flow. The ridges at the very base of the icefall are distorted and difficult to count as are the ridges at the very bottom of the photo. Approximately 20 ridges are identifiable.


  4. What type of landform does the letter C identify?

    Medial moraine; there is ice separating the moraine from the valley wall so it's not a lateral moraine.

  5. What type of landform does the letter D identify?

    Lateral moraine; unconsolidated debris along the valley wall.
Photo: glacial landforms
Photo: D. Becker. 2008. USGS Multimedia Gallery, photo BeckerDSC_4804.jpg. <http://gallery.usgs.gov/> Accessed July 2010.

  1. The letter A is pointing to Avalanche Peak. What type of landform is Avalanche Peak? How did the shape and spacing of the contour lines help you determine the type of landform?

    Avalanche Peak is an example of a horn. The contour lines are somewhat triangular shaped (blue triangle), which is typical of horns. The contour lines are also very closely spaced indicating steep sides to the horn.


  2. The letter B refers to a landform that starts at Avalanche Peak and extends north-northeast to just past the letter B. What type of landform is this? How did the shape and spacing of the contour lines help you determine the type of landform?

    The B is sitting near the end of an arete (blue line). Aretes are narrow, steep-sided ridges that extend away from horns. Aretes separate either two glacial troughs from one another or two cirques from one another. This arete separates two cirques from one another. The contour lines are closely spaced indicating steep slopes on either side of the arete. Along the top of the arete the contour lines are closed and stretched out in a direction parallel to the orientaiton of the ridge. The contour lines at the end of the arete near the letter B bend toward lower elevations (toward the creek and the lake), which is something contour lines on ridges do regardless of the type of ridge.

  3. Letter C is sitting in a lake. What type of landform is this lake an example of?

    Tarn; a lake located at the bottom of a cirque.

  4. There are two well-defined cirques on this map. Draw a line identifying the location of the headwall to each of these cirques.

    Red lines.

  5. Letter D is sitting in a valley. Draw a sketch of the shape of the valley from one side of the valley to the other side of the valley using the contour line spacing to help get the valley profile correct. Based on your sketch, was this valley most likely carved by a glacier or by the river that's currently flowing in the valley bottom? Explain.

    Your sketch should show a valley shaped like a parabola or a letter U, with a wide relatively flat valley bottom and steeper valley walls. There are no contour lines in the middle of the valley bottom where the creek and the lake are located indicating a relatively flat landscape. The contour lines along the valley walls are closer together indicating steeper slopes.

    The valley was most likely carved by a glacier not by the river that's currently flowing along the valley bottom. At these elevations, valleys carved by rivers would have much narrower valley bottoms with more of a V shape.
Topographic map: Mt. Jackson

28. Identify the following features on the photo to the right:

  • two large cirques and one smaller cirque (red lines);
  • one horn (blue diamond);
  • one arete (yellow line);
  • three cirque glaciers (labeled "cirque glacier" or "cg");
  • two valley glaciers (labeled);
  • one medial moraine (green arrow); and,
  • glacial till that is not clearly definable as an end, a medial, or a lateral moraine (labeled).
Photo: glacial landscape
Photo: B.F. Molnia. Alaskan Glaciers. U.G. Geological Survey. <http://www.usgs.gov/features/glaciers2.html> Accessed July 2010.

  Topographic map Rocky Mtn National Park.
 

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Last updated July 2010 KAL.