Nisqually glacier data chart

Glacial Processes.docx

Name: _______________________________

G205: Glaciers

A glacier is a body of ice and snow that moves under the influence of gravity and its own weight. Evidence that a glacier is moving includes crevasses, flow features on the surface of the glacier, and a stream emerging from the terminus of the glacier filled with ground rock called glacial flour.

All glaciers consist of two parts. The upper part is perennially covered with snow, and is referred to as the zone of accumulation. The lower part is the zone of ablation, where calving, melting, and evaporation occur. If, over a period of time, the amount of snow a glacier gains is greater than the amount of water and ice it loses, then the glacier will expand or advance. If the amount of water and ice a glacier loses is greater than the amount of snow it gains, then the glacier will shrink or retreat. This is referred to the mass balance of the glacier.

Figures 13.7 and 13.8 (11th)/13.3 and 13.4(10th)/Figures 13.1 and 13.2 (9th) in your lab manual show some of the unique landscape features created by mountain (also called valley) glaciers. Figures 13.15 and 13.16 show common features created by continental glaciers. Glaciers, especially valley glaciers, can be thought of as "rivers" of ice. In many ways, the rules governing stream flow also govern the flow mechanism of glacial ice. Just as flowing water will naturally seek out the lowest elevation, so will glaciers. Once the glacial ice of a valley glacier begins to flow downslope, the glacier occupies a valley that was formerly cut by stream erosion, thus changing its shape form a "V"-shaped stream valley to a "U"-shape profile that is flat at the base but very steep along the valley walls.

This lab examines the landscapes associated with both types of glaciers, and also the response of glaciers to climate change.

Part 1: Glacier Movement – Deformation or Basal Sliding?

Glacier Model

Materials:

10 ml Borax powder

Airtight container or zip-lock bag

325 ml warm water

Chute made from PVC pipe or cookie sheet

250 ml white glue

Tape/Rubber Bands

2 mixing bowls

Ruler

Mixing spoon

Timer

Food coloring (optional)

Plastic drinking straw or spray bottle and water

Process:

1. Make the glacier gak (already made, but you can make it at home, too):

a. In the first mixing bowl, combine 200 ml warm water and 250 ml glue. Stir until well mixed.

b. In the second mixing bowl, combine 125 ml warm water and 10 ml of Borax powder. Stir until the powder is fully dissolved.

c. Combine the contents of the two mixing bowls. Stir until a single glob forms and cleans the sides of the bowl.

d. Optional: use food coloring to create different gak colors. Put half of the glob back into the first mixing bowl and add a few drops of food coloring. Knead the mixture, wearing rubber gloves to prevent staining your hands with the food coloring, until it is well mixed. Use the alternating colors in the experiment or smush the strips together to form a single striped glob of gak.

Experiment #1

1. Prop up one end of the PVC pipe chute (with books, rocks, etc.) so the glacier will be able to flow downhill. Think about the angle of repose from the mass wasting lab when deciding on how steep the chute might need to be.

3. Place the entire “glacier” at the top of the chute. Use the dry erase marker to mark the position of the front end of the glacier (the terminus), and the right and left sides of the glacier.

4. Set your timer for 5 minutes.

5. At the end of 5 minutes, mark the new location of the glacier terminus.

6. Take the chute down and place on a level surface to prevent further forward movement.

7. Measure and record the distance the glacier traveled from start to finish at the center, the left side, and the right side of the glacier. Repeat to obtain an average. Record the results in the table below. Determine the velocity of the three sections using the distance traveled from the table above and the elapsed time of 5 minutes. Don’t forget to convert minutes to seconds. Record the values in the table below.

Distance traveled by the glacial model (cm)

First Trial (cm)

Second Trial (cm)

Average (cm)

Velocity (cm/sec)

Right side

Center

Left Side

8. When the glacier model initially flowed, what shape did the front of the glacier take (sketch it)?

9. What part of the glacier flowed fastest? Why?

10. Does this experiment more closely approximate glacial movement by deformation of the ice or by basal sliding?

11. What are your predictions for how the glacier will flow when a little water is added to the chute added compared to the first time you ran the experiment?

Experiment #2

1. Set up the experiment again, marking the terminus of the glacier.

13. Poke the plastic drinking straw through the glacier, as close to the top of the glacier as possible. Add 5 ml of water through the straw to simulate meltwater seeping down through the glacier. Alternatively, lightly mist the chute with water from the spray bottle.

14. Set your timer for 5 minutes.

At the end of 5 minutes, measure the distance the glacier traveled from start to finish at the center, the left side, and the right side of the glacier. Repeat and record the results in the table below. Determine the velocity of the glacier with basal water. Record the values in the table below.

Distance traveled by the glacial model (cm)

First Trial (cm)

Second Trial (cm)

Average (cm)

Velocity (cm/sec)

Right side

Center

Left Side

15. Describe the difference between the glacial velocities of the two experiments. Why do you think this change occurred?

Part 2: Mountain Glaciers on Topographic Maps

In this part you will examine the features associated with mountain glaciers using Activity 13.2 (10th)/Activity 13.1 (9th) in your lab manual (10th: p. 349-350/9th: 309-310). Read the instructions in your lab manual and address the modified questions in the space below.

 PART A

A.1 and A.2: Complete the profiles on the graph to the right.

A.3: Which of the cross-sections you made is V-shaped? (S-T or G-L?)

A.4: Which cross-section is U-shaped? (S-T or G-L?)

Why do you think a valley carved by a glacier has a different shape than that of a river?

A.5: Complete the topographic profile for A-B across the Harvard glacier on the right.

Label the top surface of the glacier on your profile, and put a dashed line where you think the rock bottom of the valley (or bottom of the glacier) is.

Based on the profile you constructed, what is the maximum thickness of Harvard Glacier along line A-B?

PART B. Read the instructions for this part and answer the associated questions on the space below:

B1:

B2:

PART C: Read the instructions for this part and answer the associated question in the space bellow.

Part 3: Glaciation in Glacier National Park, Montana

Use Figure 13.14 (10th p. 343)/Figure 13.12 (9th p. 305) (Glacier National Park, MT) in the lab manual to find a few glacial landforms. More specifically, list an example of a glacial erosional landform, depositional landform and water body present in this region (the features are listed on pages 335-337 of the lab manual) in the following table.

Type of Glacial Landform

Name on map/General location

Erosional Feature

1.

2.

Depositional Feature

1.

2.

Water Body

1.

2.

16. Using the data provided in the lower right corner of the Glacier National Park map, by what percentage did each of the glaciers below decrease in size between 1850 – 1993? [Hint: ((Initial – Final)/Initial) x 100]

a. Agassiz Glacier ____________________________.

b. Vulture Glacier ____________________________.

17. What was the rate (in km2/yr) that each of the glaciers receded between 1850 and 1993? [Hint: (Initial – Final)/# of Years]

a. Agassiz Glacier ____________________________.

b. Vulture Glacier ____________________________.

18. Based on what you calculated in the question above, in what year will each of these glaciers be completely melted? [Hint: Final/Rate + 1993]

a. Agassiz Glacier ____________________________.

b. Vulture Glacier ____________________________.

Part 4: Continental Glaciation and Landforms on Topographic Maps

In this part you will be examining the effects of continental glaciation on a landscape by viewing topographic maps from Ontario, Canada and Wisconsin. You will essentially be completing most of Activity 13.3 (10th p. 351)/13.2 (9th p. 311) in your lab manual and addressing the questions in the space below. Don’t forget to use Figures 13.8 & 13.9 (10th p. 338/9th p. 301) when addressing these questions!

A1.

A2.

A3. Towards what direction did the glacial ice flow here, and how can you tell?

B1.

B2.

B3.

B4.

B5.

Part 5: Nisqually Glacier and Climate Change

In this part you will be examining data from the Nisqually Glacier of Mt. Rainier, Washington. You are asked to complete most of Activity 13.5 (10th)/Activity 13.4 (9th) (10th: p. 353-354/9th: p. 313-314) in your lab manual, and record your answers in the space below.

PARTS A & B: Read the instructions to parts A & B, then complete the data chart and graph as instructed and then answer the questions below.

C1:

D:

E:

BONUS SECTION! Glacial Landforms and Google Earth

Open Google Earth and type in 63.069323°, -151.006058° in the Search window. Be sure that you have Borders and Labels check-marked in the Layers window in the left-hand panel. Google Earth will zoom in very close so you’ll have to zoom out to answer all the questions below. This section is worth an extra 6 points added on to your lab score, if you choose to do this.

1. What peak is at this location? To which mountain range does it belong? In which state is it located?

2. Locate and identify four glacial features in this area and identify their location using latitude and longitude (in decimal degrees, as we have done before, and as shown above), and put your results in the table below. You might use the figures in your lab manual for ideas.

Feature

Latitude and Longitude

1

2

avg. distance

time

velocity

=

Glacier Lab Handout.pdf

Chapter13.pdf

1 13 Glaciers and the Dynamic Cryosphere C O N T R I B U T I N G A U T H O R S

Sharon Laska • Acadia University

Kenton E. Strickland • Wright State University–Lake Campus

Nancy A. Van Wagoner • Acadia University

L A B O R A T O R Y

BIG IDEAS Earth’s crysphere is its snow and ice (frozen water),

including permafrost, sea ice, mountain glaciers,

continental ice sheets, and the polar ice caps. The extent

of snow and ice in any given area depends on how much

snow and ice accumulates during winter months and

how much snow and ice melts during summer months.

Glaciers are one of the best known components of the

cryosphere, because they are present on all continents

except Australia and have created characteristic

landforms and resources utilized by many people.

FOCUS YOUR INQUIRY THINK About It |

What is the cryosphere, and how do changes in the cryosphere affect other parts of the Earth system?

ACTIVITY 13.2 Mountain Glaciers and Glacial Landforms (p. 330 )

ACTIVITY 13.3 Continental Glaciation of North America (p. 330 )

How is the cryosphere affected by climate change?

THINK About It |

ACTIVITY 13.4 Glacier National Park Investigation (p. 334 )

ACTIVITY 13.5 Nisqually Glacier Response to Climate Change (p. 334 )

ACTIVITY 13.6 The Changing Extent of Sea Ice (p. 335 )

ACTIVITY 13.1 Cryosphere Inquiry (p. 330 )

THINK About It | How do glaciers affect landscapes?

Introduction The cryosphere is all of Earth’s snow and ice (frozen water). It all begins with a single snowflake falling from the sky or a single crystal of ice forming in a body of water. Over time, a visible body of snow or ice may form. Most snow and ice melts completely over summer months, providing much-needed water to communities. However, there are areas of Earth’s surface where the annual amount of ice accumulation exceeds the annual amount of ice melting. Permanent masses of ice can exist there. These areas ( FIGURE 13.1 ) range from places with permanently frozen ground (permafrost), to places

329

Kennicott Glacier, a long (43 km, 27 mi) valley glacier in Alaska. Mountains in the distance are where snow and ice accumulate and form the glacier. Down valley, dark medial moraines of rocky drift are deposited from melting ice. (Photo by Michael Collier)

PRE-LAB VIDEO

330 ■ L A B O R AT O R Y 13

where ice permanently covers the ground (glaciers and ice caps, ice sheets), to places where ice covers parts of the ocean (ice shelves, sea ice). The ice in your freezer may last for days or months, but ice in some of Earth’s ice caps is thousands of years old.

OBJECTIVE Analyze features of landscapes aff ected by mountain glaciation and infer how they formed.

PROCEDURES

1. Before you begin , read the Introduction, Glaciers, and Glacial Processes and Landforms. Also, this is what you will need :

____ ruler, calculator ____ Activity 13.2 Worksheets (pp. 349–350 ) and

pencil

2. Then follow your instructor’s directions for completing the worksheets.

ACTIVITY 13.2 Mountain Glaciers and

Glacial Landforms

THINK About It | How do glaciers affect landscapes?

ACTIVITY 13.1 Cryosphere Inquiry

THINK About It |

What is the cryosphere, and how do

changes in the cryosphere affect other

parts of the Earth system?

OBJECTIVE Analyze global and regional components of the cryosphere, and then infer how they may change and ways that such change may aff ect other parts of the Earth system.

PROCEDURES

1. Before you begin , do not look up defi nitions and information. Use your current knowledge, and complete the worksheet with your current level of ability. Also, this is what you will need to do the activity:

____ pen ____ Activity 13.1 Worksheets (pp. 347–348 ) and

pencil

2. Complete the worksheet in a way that makes sense to you.

3. After you complete the worksheet , be prepared to discuss your observations and classifi cation with other geologists.

OBJECTIVE Analyze features of landscapes aff ected by continental glaciation and infer how they formed.

PROCEDURES

1. Before you begin , read the Introduction, Glaciers, and Glacial Processes and Landforms. Also, this is what you will need :

____ Activity 13.3 Worksheet (p. 351 ) and pencil

2. Then follow your instructor’s directions for completing the worksheets.

ACTIVITY 13.3 Continental Glaciation of

North America

THINK About It | How do glaciers affect landscapes?

Dynamic Cryosphere The total amount of ice on Earth’s surface is ever- changing due to annual variations in global patterns of air circulation and regional variations in things like ground temperature, ocean surface temperature, and the weather (daily to seasonal conditions of the atmosphere, such as air temperature and humidity, wind, cloud cover, and precipitation). Global and regional amounts of ice are also affected by climate —the set of atmospheric conditions (like air temperature, humidity, wind, and precipitaion) that prevails in a region over decades. A region’s climate is generally determined by measuring the average conditions that exist there over a period of years or the conditons that normally exist in the region at a particular time of year.

Climate Change A region’s climate is based on factors like latitude, altitude, location relative to oceans (moisture sources), and location relative to patterns of global air and ocean circulation. Climate change refers to a significant change in atmospheric conditions of a region or the planet. This can occur due to natural factors like changing patterns of global air circulation, variations in volcanic activity, and changes in solar activity. It can also occur due to human factors like construction of regional urban centers (adding regional sources of heat energy) and deforestation (removing a transpiration source of atmospheric water vapor; adding soot and gases to the atmosphere as the forest is burned).

Glaciers and the Dynamic Cryosphere ■ 331

Map of Regional Variations in the Cryosphere

ICE SHELF: A sheet of ice attached to the land on one side but afloat on the ocean on the other side.

SEA ICE: A sheet of ice that originates from the freezing of seawater.

SEASONAL SNOW: Snow and ice may accumulate here in winter, but it melts over the following summer.

PERMAFROST CONTINUOUS: The ground is permanently frozen over this entire area.

PERMAFROST DISCONTINUOUS: The ground is permanently frozen in isolated patches within this area.

ICE SHEET: A pancake-like mound of ice covering a large part of a continent (more than 50,000 km2).

MOUNTAIN GLACIERS AND ICE CAPS: This area contains permanent patches of ice on mountain sides (cirques), river-like bodies of ice that flow down and away from mountains (valley and piedmont glaciers), and dome-shaped masses of ice and snow that cover the summits of mountains so that no peaks emerge (ice cap).

• South Pole

• North Pole

FIGURE 13.1 Cryosphere components. You can also download a complete world map of cryosphere components from this UNEP

(United Nations Environment Programme) website: http://www.grida.no/graphicslib/detail/the-cryosphere-world-map_e290

Glaciers Glaciers are large ice masses that form on land areas that are cold enough and have enough snowfall to sus- tain them year after year. They form wherever the win- ter accumulation of snow and ice exceeds the summer ablation (also called wastage ). Ablation (wast- age) is the loss of snow and ice by melting and by sublimation to gas (direct change from ice to water vapor, without melting). Accumulation commonly occurs in snowfields —regions of permanent snow cover ( FIGURE 13.2 ).

Glaciers can be divided into two zones, accumulation and ablation ( FIGURE 13.2 ). As snow and ice accumulate in and beneath snowfields of the zone of accumulation , they become compacted and highly recrystallized under their own weight. The ice mass then begins to slide and flow downslope like a very viscous (thick) fluid. If you slowly squeeze a small piece of ice in the jaws of a vise or pair of pliers, then you can observe how it flows. In nature, glacial ice formed in the zone of accumulation flows and slides downhill into the zone of ablation , where it melts or sublimes (undergoes sublimation) faster than new ice can form. The snowline is the boundary between the zones of accumulation and ablation. The bottom end of the glacier is the terminus .

It helps to understand a glacier by viewing it as a river of ice. The “headwater” is the zone of accumula- tion, and the “river mouth” is the terminus. Like a river, glaciers erode (wear away) rocks, transport their load

(tons of rock debris), and deposit their load “down- stream” (down-glacier).

The downslope movement and extreme weight of glaciers cause them to abrade and erode (wear away) rock materials that they encounter. They also pluck rock material by freezing around it and ripping it from bedrock. The rock debris is then incorporated into the glacial ice and transported many kilometers by the glacier. The debris also gives glacial ice extra abrasive power. As the heavy rock-filled ice moves over the land, it scrapes surfaces like a giant sheet of sandpaper. Rock debris falling from valley walls commonly accumulates on the surface of a moving glacier and is transported downslope. Thus, glaciers transport huge quantities of sediment, not only in, but also on the ice.

When a glacier melts, it appears to retreat up the valley from which it flowed. This is called glacial retreat , even though the ice is simply melting back (rather than moving back up the hill). As melting occurs ( FIGURE 13.3 ), deposits of rocky gravel, sand, silt, and clay accumulate where there once was ice. These deposits collectively are called drift . Drift that accumulates directly from the melting ice is unstratified (unsorted by size) and is called till . However, drift that is transported by the meltwater becomes more rounded, sorted by size, layered, and is called stratified drift . Wind also can transport the sand, silt, and clay particles from drift. This wind-transported sediment can form dunes or loess deposits (wind-deposited, unstratified accumulations of clayey silt).