INTRODUCTORY ACTIVITY: SETTING THE STAGE
1. Begin the class by asking students what they know about the Ice Age. (Accept all answers.) What evidence is left of the Ice Age? (Existing glaciers, erosion and other evidence of glaciation.) Ask for a short and simple description of a glacier. (You will probably get something like “a sheet of ice.”) Tell students that a glacier is a huge mass of ice slowly flowing over a land mass, formed from compacted snow in an area where snow accumulation exceeds melting and sublimation. Glaciers, ice sheets, and ice caps have affected much of the Earth as we know it today, including landforms such as valleys, lakes, and mountain peaks, as well as other factors such as weather patterns and sea levels.
2. Tell students that in order to discuss glaciers and recognize their effects on the landscape of the Earth, they must know the terminology to describe different parts of a glacier and glaciation. Have students (either in pairs or in groups, depending on how many computers your classroom has) open the “Our Environment: Glaciers” interactive. Distribute the “Glacier Overview Organizer” (PDF)(RTF) to each student. If possible, display the interactive on a screen for the whole class as well. Read the first page to the class, or ask a student to read it aloud.
3. Ask students to read the information and study the pictures of valley glaciers on the next two pages. Give students a FOCUS FOR MEDIA INTERACTION by asking them to note the landforms and features specific to valley glaciers. Students should click through the pages using the green arrow in the bottom right corner. They should record their observations on the Glacier Overview Organizer. Give students 5-10 minutes to complete this part of the activity. Check for comprehension by asking students to point out the features on the image in the interactive.
4. Ask students to move on to the next two pages of the interactive, which describe continental glaciers. Give students a FOCUS FOR MEDIA INTERACTION by asking them to note features of continental glaciers, and to compare and contrast these with valley glacier features. Give students 5-10 minutes to complete this part of the activity. Check for comprehension by asking students to point out the features on the image in the interactive.
5. Ask students how they think glaciers cause and create all of these features. (Melting, moving, eroding.)
LEARNING ACTIVITY 1
1. Tell students that the process by which a glacier is formed can be long and complex – it isn’t just a large amount of water freezing over the winter. Have students, in pairs or groups, visit the Life Cycle of a Glacier interactive. Give students a FOCUS FOR MEDIA INTERACTION by asking them to note what happens to the snowflake as the glacier forms. Where does it start? Where does it end up? Distribute the “Life Cycle of a Glacier Organizer” (PDF)(RTF) to students and have them answer the questions as they go through the interactive. Check for comprehension by reviewing the answers on the Organizer. (Answer Keys for all the student organizers are available in the Materials list on the Overview page).
2. Have students remain in pairs or groups. Give each student 5 oz. of play dough, which they should spread out their lab tables or desks. Distribute model glaciers from the ice cube trays to each student and tell them that they will be demonstrating what happens as glaciers move across surfaces. Each student will scrape his or her glacier, gravel end down, over the play dough. In order to accurately simulate the action of a real glacier, students should scrape relatively slowly in only one direction, using a fair amount of pressure. Have students write in their notebooks about the kind of impressions the “glacier” makes in the play dough. Are gravel pieces or other debris left behind? Does the “glacier” scratch through the play dough? When scraping is completed, ask students to rest their ice cubes on paper plates and allow them to melt.
3. Ask students to look closely at the “glacier.” Do they notice any interesting surface features like crevasses? How is the sediment (dirt and gravel) distributed throughout? (Randomly.) How was the play dough “landscape” affected by the sediment in the “glacier”? (Scratches, grooves, possibly erratics, which are large boulders picked up and then deposited by glaciers.) Explain that glaciers form on top of rocks and dirt but also pick up additional sediment as they move; these can be rock fragments from valley walls or new rocks from the ground that freeze into the ice. These rocks act as gougers and produce glacial grooves and scratches in bedrock that show patterns of glacial movement.
4. Observe the melting “glacier” on the paper plate. This is more similar much closer to a continental glacier, while the scraping activity represented a valley glacier. What do students notice about how the sediments are distributed by the melting ice? (Sediment is unsorted, piles are of mixed sizes.)
LEARNING ACTIVITY 2
1. Now that students have witnessed some of the effects of glaciation, ask them if they are familiar with any landscapes that may have been affected by glaciers. (Accept all reasonable answers.) Tell students they are going to watch a short video clip about glaciers’ effects on the landscape of Ireland. Play Clip 1, “Forming the Burren.” (Access the video segments for this lesson at the Video Segments Page.) Give students a FOCUS FOR MEDIA INTERACTION by asking them to write down at least two ways in which Ireland’s landscape was changed by glaciation. When clip is finished, ask students to share their answers. (Scouring, gouging, depositing erratics, depositing soils and sediments, forming grikes.) Explain that there are two ways in which glaciers create new landforms: erosion and deposition.
2. Explain that there are three main types of glacial erosion:
- Freeze-thaw, which is the action of glacial water on cracks or hollows in rock surfaces. Water expands/freezes and contracts/thaws in the cracks, which eventually causes the rocks to break up.
- Plucking, which occurs when the glacier moves over land. Rocks freeze to the base and are picked up from the ground, proceeding to move with the glacier.
- Abrasion, which occurs when rocks at the base of the glacier rub against the bedrock and wear on the landscape.
The processes do not necessarily happen in isolation; any two or all three can happen at the same time as a glacier advances.
3. Explain that we can learn about glaciers from their effects on the landscape. Display the satellite image of New York for the whole class. This area was covered by glaciers in the Ice Age. What do students see on this map that might be a result of glacial erosion? (Finger Lakes, Hudson River, lakes in Canada, possibly grooves in New Jersey) Based on the orientation of the Finger Lakes, in which direction can we assume the glacier traveled? (North-south.) Ask students to speculate on how the lakes might have formed. (Glaciers eroded depressions, gouged, filled with meltwater.) Tell students that it is currently believed that the Finger Lakes were previously existing stream valleys that were widened and deepened by glacial erosion and then filled with meltwater.
4. Refer back to the satellite image of New York. Remind students that in addition to erosion, glacial deposition creates landforms as well. Glacial deposition occurs when the glacier, through its movement, deposits rocks and debris it has picked up along the way. Point out the large moraine in Central New York that serves to dam the Finger Lakes. Explain that this is a terminal moraine, indicating the furthest advance of the glacier. Ask students if they can find other landforms on the map created by glacial deposition. (Ronkonkoma moraine, Valley Head moraine, drumlin field, outwash plain)
5. Briefly review the key vocabulary terms from the introductory activity. Tell students they’ll be watching another video clip showing examples of glaciated landscapes. Play Clip 2, “Glaciated Landscape” without sound, so that students may notice the glacial features on their own, without being informed or biased by the narration. (Access the video segments for this lesson at the Video Segments Page.) Give students a FOCUS FOR MEDIA INTERACTION by asking them to list the different glacial features they notice in the clip. Check for comprehension by replaying the clip and having students call out the features as they see them. (Kettles, U-shaped valley, arête, drumlins, moraines, eskers)
1. Tell students that in addition to shaping the landscape of the Earth, glacial advance and retreat can have a major impact on the Earth’s climate. Students should remember from the beginning of the lesson that glaciers are a remnant from the last Ice Age. Ask students approximately when the last Ice Age occurred. (Students can consult Earth Science reference tables. Last Ice Age was in Pleistocene Epoch, between 0.01 and 1.6 million years ago.) Explain that currently the common belief is that the Earth is in a cyclical pattern of Ice Ages and warmer periods called interglacials, and that the Earth has experienced many of these cycles. Ask students to speculate on what might cause these cycles. (Accept all answers.) Tell students that glacial retreat affects conditions on our planet, such as sea levels and animal habitats. Additionally, as ice caps get smaller they reflect less sunlight, which affects weather patterns and climate. Explain that since much of the water trapped in ice sheets is freshwater, as the ice caps melt the salt content of the oceans may be affected. Ask students how they think this might impact the Earth. (Change in ocean currents, destruction of animal habitats.)
2. Explain that while many factors may contribute to the cyclical pattern, some scientists now believe that human-influenced global warming is altering and accelerating the natural cycle. There is evidence throughout geological history that warm “interglacial” periods usually coincide with high atmospheric levels of methane and carbon dioxide. Why might this indicate that humans have some responsibility for climate change? (Industrial Revolution, humans using machinery/animals/agricultural processes releasing these gases into the atmosphere) Direct students (individually, in pairs, or in groups, depending on how many computers are in your classroom) to the Milankovitch Cycles interactivity. Distribute the “Milankovitch Cycles Organizer” (PDF)(RTF) to each student. Ask students to go through each page of the interactive. Give students a FOCUS FOR MEDIA INTERACTION by asking them to note where in the three cycles the Earth is currently. Students should complete the questions on the organizer as they go through the interactive. Check for comprehension by reviewing the answers on the Organizer.
3. For homework, have students write a short paper on climate change and glacial retreat. Students should give their opinions, based on class discussion and other sources, about whether climate change is part of an established pattern or humans are affecting the warming cycle. They should include specific examples to support their opinions.
CROSS CURRICULAR EXTENSIONS
The Northwest Passage is a sea route through the Arctic Ocean, which for many years was difficult to navigate due to the presence of Arctic ice. By 2007, the ice had melted enough for the passage to be opened for regular crossing. Discuss the pros and cons of the recent opening of the Northwest Passage. Do the trade benefits outweigh the environmental issues?
Ask students to use play dough to create models of glaciated landscapes, including features they have learned about.
Ask students to determine what natural processes have shaped the landscape in their region, using aerial and topographical maps of the area.
If a university is present in the immediate area, ask someone from the geography department or geology department to discuss the most recent Ice Age with your students.