Changing Planet: Melting Glaciers
Students sort photographs of glaciers and measure glacial retreat to observe how alpine glaciers have retreated over the past century.
Adapted by NESTA/Windows to the Universe team members Missy Holzer, Jennifer Bergman, and Roberta Johnson from the Glaciers: Then and Now activity on Windows to the Universe.
Student Learning Outcomes:
Hands-on activity, data analysis, and class discussion
- For background information on melting alpine glaciers watch Changing Planet: Melting Mountain Glaciers. Also explore these topics on the Windows to the Universe website at the links listed below.
- To begin this lesson explain what glaciers are, how glaciers grow and retreat, and the two types of glaciers: continental and valley (or alpine) glaciers. Discuss the climate conditions that are necessary for a glacier to grow (snowy winters and cool summers). Discuss the climate conditions that are necessary for a glacier to shrink (warmer). You may want to use the Model a Moving Glacier inquiry-based activity to introduce the concept of glaciers and glacial movement. Otherwise, use the resources from this lesson to develop an introduction to this concept ensuring students understand how and where glaciers form.
- Prior to this lesson print enough copies of the Melting Glaciers Photo Pairs so there is a set for each team of two or three students. Cut each sheet of paper in half to separate the glacier photos. You may want to laminate the photos for durability. Do not share the first page with students until they have matched all the pairs. This investigation can be done without Google Earth although students gain a better spatial understanding of the distribution of glaciers while using this valuable tool. If you do plan on using it, be sure that it is installed and the NSIDC Glaciers and Climate Change Google Earth File is accessible for viewing before using this lesson.
- Ask students if they think that glaciers would be affected by climate change and if glaciers can be used to understand how the climate has changed over the past 100 years. Show students the 1993 and 2000 Landsat images of Kilimanjaro and discuss the changes in one image to the next.
- For Part 1 of this lesson, teams of two or three students try to match the glacier images from the past and present. Mention that the students are now going to view photos of Alaskan alpine glaciers to look for changes over time. Give them approximately 15 minutes to accomplish the task. Next, have students compare their results with neighboring teams.
- Refer students to their worksheet to record their observations of the glaciers and landforms in the photographs. Allow students to access Google Earth or the Internet to determine the latitude and longitude of each glacier.
- Discuss the images and reveal the correct matches. Ask students to answer the questions for Part 1.
- In Part 2, students measure the rate of retreat of a Gangotri Glacier, Uttarakand in the Himalayan Mountains. Allow students to use Google Earth to locate this glacier. Next, students use rulers and the scale at the base of the map to measure the distance the glacier retreated over the timeframe presented. They may need assistance with converting map scale to the actual scale on the Earth. Monitor student progress to ensure they properly convert the map scale to kilometers on the Earth.
- Assist students with the analysis questions which requires them to solve problems. Next students work with their partner(s) in answering the conclusion and application questions. Once they have completed all the tasks, bring the class together for a group discussion about the activity that includes ways to investigate this issue further from a scientific viewpoint and from a human population viewpoint.
Assess students on their accuracy in sorting, observing, measuring and making conclusions related to this investigation. Additionally ask students to pretend they are from the area of one of these glaciers and they have seen these changes that have taken place over their lifespan, and have them write a story about their observations. Encourage them to go beyond identifying only the changes they have seen in the glaciers and to discuss the changes they have seen in the plants and animals too. This activity will require extra time and references to complete.
Always use safe laboratory practices.
Store materials for future use.
- For older students, the USGS Benchmark Glacier program has glacier mass balance, temperature and runoff temporal data for a glacier in Washington State, and for two in Alaska. The raw data can be accessed and students can make their own plots, or the plots on the website can be used to analyze the changes in these glaciers over time.
- The Intergovernmental Panel on Climate Change has a plot of the retreat of alpine glaciers from around the world. The data are not exactly linear, and this fact can be part of an interesting discussion and additional research on the topic of retreating glaciers.
BACKGROUND INFORMATION:For a glacier to develop, the amount of snow that falls must be more than the amount of snow that melts each year. This means that glaciers are only found in places where a large amount of snow falls each year and where it is so cold year-round that at least some of the snow does not melt. Cold climates where glaciers are found exist both in Earth's polar regions and in high altitude locations at all latitudes.
- Continental glaciers, also called ice sheets, cover large amounts of land in the Earth's polar regions. The largest ice sheets are located in Antarctica. In the Arctic region, an ice sheet covers Greenland and there is an ice sheet in Iceland. During the most recent Ice Age (approximately 15,000 years ago) a large continental glacier covered much of the northern part of North America. It is long gone, but has left behind a record of where it traveled in the rocks, sediments, and the shape of the land.
- Alpine glaciers are found in high mountain valleys worldwide. Alpine glaciers are responsible for carving mountains into distinctive shapes leaving pointed ridges between glaciers, u-shaped valleys where the glacier moved through, and hills of rock debris called moraines that were pushed by the glacier. Today, because of rapid global warming, alpine glaciers that are at tropical and mid-latitudes are melting very quickly.
Snow that falls on a glacier may eventually become part of the glacial ice. The snowflakes become buried under more and more snow, eventually changing their shape because of the pressure from the layers of snow above and becoming part of the massive ice. Over time the ice crystals become so closely packed that the tiny pockets of air between them are squeezed out and the ice changes in color from white to blue.
Glaciers are not just giant ice cubes. All that ice can be a powerful force. Glaciers move over time scraping rock from the Earth's surface, bulldozing boulders, gravel, and sand into hills called moraines, and sending ice out over the ocean in massive ice shelves.
How does a glacier move? Under the pressure of its own weight, glacial ice flows downhill over time. If you were to touch a glacier's ice, it would feel solid and cold, just like ice usually feels, but over a long time it flows like honey. Glaciers also move downhill by sliding at their base, a process called basal slip. The pressure on the ice that is at the bottom of a glacier causes some of that ice to melt producing a slippery little layer upon which the rest of the ice can slide.
Today, observations show that in most places around the world, alpine glaciers are in retreat. Glaciers in Glacier National Park in Montana are disappearing so fast that research indicates that they will be gone by 2030. Mt. Kilimanjaro, Africa's highest mountain, will soon be entirely without glaciers. Research has shown that it has had glaciers on it for almost 12,000 years. However, in the past century the ice has diminished by 80% and scientists report that the glaciers on Kilimanjaro will have entirely melted by 2015-2020. Simulations of glacier and ice sheet melting show that if all glaciers and ice sheets melt worldwide, sea level will rise approximately 70 meters.
RELATED SECTIONS OF THE WINDOWS TO THE UNIVERSE WEBSITE:
- The Retreat of Mt. Kilimanjaro's Ice Cap Since 1912
- Byrd Polar Research Center: Tanzania: Mt. Kilimanjaro Project
- National Snow and Ice Data Center: Glaciers