Activity 13.2 Mountain Glaciers And Glacial Landforms

Mountain glaciers, those rivers of ice carving through towering peaks, are not just stunning natural wonders. They are powerful agents of erosion, transportation, and deposition, shaping the very landscapes they inhabit. Understanding mountain glaciers and glacial landforms is crucial for comprehending Earth's dynamic processes and the dramatic transformations that have occurred over millennia. This activity explores the fascinating world of mountain glaciers and the unique landforms they create.

What are Mountain Glaciers?

Mountain glaciers, also known as alpine glaciers, are masses of ice that form in high-altitude regions where temperatures are cold enough to allow snow to accumulate over time. This accumulated snow compacts and transforms into dense glacial ice. Gravity then pulls the ice downhill, causing the glacier to flow like a very slow-moving river.

Key Characteristics of Mountain Glaciers:

• Formation: They form in areas where snowfall exceeds snowmelt over many years.
• Location: Typically found in mountainous regions.
• Movement: They move downslope due to gravity and internal deformation of the ice.
• Size: They range in size from small cirque glaciers to large valley glaciers that can stretch for many kilometers.
• Temperature: Glacial ice is cold, but the base of the glacier can be at or near the pressure melting point due to the immense weight of the ice above.

Types of Mountain Glaciers:

• Cirque Glaciers: These small glaciers occupy bowl-shaped depressions called cirques, often found high on mountain slopes. They are the birthplace of many larger glaciers.
• Valley Glaciers: These glaciers are confined to valleys and flow downhill like rivers of ice. They are often fed by cirque glaciers.
• Piedmont Glaciers: These form when valley glaciers flow out onto a plain at the foot of a mountain range. They spread out into a broad, fan-shaped lobe.
• Hanging Glaciers: These cling to steep cliffs and are often the source of dramatic icefalls.

How Mountain Glaciers Shape the Landscape: Glacial Processes

Mountain glaciers are powerful agents of erosion, transportation, and deposition. They shape the landscape through a variety of processes:

Erosion

Glaciers erode the landscape in several ways:

• Plucking (Quarrying): As a glacier moves, meltwater seeps into cracks in the bedrock. When this water freezes, it expands, exerting pressure on the rock and causing it to fracture. The glacier then plucks away these loosened pieces of rock as it flows. This process is particularly effective on the down-valley side of bedrock bumps, creating a jagged, uneven surface.
• Abrasion: Glaciers act like giant rasps, grinding down the bedrock beneath them. Rocks and debris embedded in the ice scrape against the underlying surface, smoothing and polishing the rock. This process creates glacial striations (scratches) and grooves on the bedrock, providing valuable information about the direction of ice flow. The finer material produced by abrasion is called glacial flour, which gives meltwater streams a milky appearance.
• Ice Segregation: The repeated freezing and thawing of water within the pores and cracks of rocks. As water freezes, it expands, exerting pressure that can cause rocks to fracture and disintegrate. This process is particularly effective in areas with frequent freeze-thaw cycles, such as high-altitude mountain environments.

Transportation

Glaciers are highly effective at transporting vast quantities of sediment. They can carry debris of all sizes, from fine silt to massive boulders, over long distances.

• Englacial Transport: Debris carried within the ice itself. This material may have been incorporated into the glacier through plucking, abrasion, or avalanches.
• Supraglacial Transport: Debris carried on the surface of the glacier. This material may have fallen onto the glacier from surrounding slopes or been deposited by wind.
• Subglacial Transport: Debris carried beneath the glacier. This material is often subjected to intense abrasion and grinding.

Deposition

When a glacier melts, it deposits the sediment it has been carrying. This sediment is called glacial till and is typically unsorted, meaning that it contains a mixture of particle sizes ranging from clay to boulders.

• Moraines: These are accumulations of till deposited at the edges or base of a glacier. There are several types of moraines:
  • Lateral Moraines: Form along the sides of a glacier.
  • Medial Moraines: Form when two glaciers merge and their lateral moraines combine.
  • Terminal Moraines: Form at the terminus (end) of a glacier, marking its furthest extent.
  • Ground Moraine: A thin, widespread layer of till deposited beneath a glacier.
• Outwash Plains: These are broad, gently sloping plains formed by meltwater streams flowing away from the glacier. The meltwater carries sediment, which is deposited in layers, creating a sorted deposit of sand and gravel.
• Kettles: These are depressions formed when blocks of ice are buried in outwash plains. When the ice melts, it leaves behind a kettle hole, which may fill with water to form a kettle lake.
• Eskers: These are long, sinuous ridges of sand and gravel deposited by meltwater streams flowing beneath the glacier.
• Kames: These are irregular mounds or hills of sand and gravel deposited by meltwater streams on or beside the glacier.
• Drumlins: These are streamlined, elongated hills of till formed beneath the glacier. They are typically aligned parallel to the direction of ice flow.

Distinctive Glacial Landforms

The processes of glacial erosion and deposition create a variety of distinctive landforms. Some of the most common glacial landforms include:

• Cirques: Bowl-shaped depressions carved out by cirque glaciers. They often have steep headwalls and a gently sloping floor.
• Arêtes: Sharp, knife-edged ridges that separate two cirques.
• Horns: Pyramidal peaks formed when three or more cirques erode towards each other. The Matterhorn in the Swiss Alps is a classic example.
• U-Shaped Valleys: Glaciers carve out valleys with a characteristic U-shape, in contrast to the V-shaped valleys carved by rivers. The U-shape is a result of the glacier's ability to erode both the valley floor and the valley walls.
• Hanging Valleys: Tributary valleys that are left hanging high above the main valley floor. They are formed when a smaller glacier joins a larger glacier, and the larger glacier erodes the main valley more deeply.
• Fjords: U-shaped valleys that have been flooded by the sea. They are common in coastal areas that have been glaciated, such as Norway, Alaska, and New Zealand.
• Roches Moutonnées: Asymmetrical bedrock hills that have been shaped by glacial erosion. They have a smooth, gently sloping up-valley side (stoss side) and a steep, jagged down-valley side (lee side). The stoss side is typically abraded, while the lee side is plucked.
• Striations: Scratches and grooves on bedrock surfaces caused by abrasion. They provide valuable information about the direction of ice flow.
• Moraines: Ridges of till deposited at the edges or terminus of a glacier.
• Outwash Plains: Broad, gently sloping plains formed by meltwater streams flowing away from the glacier.
• Kettles: Depressions formed when blocks of ice are buried in outwash plains.
• Eskers: Long, sinuous ridges of sand and gravel deposited by meltwater streams flowing beneath the glacier.
• Kames: Irregular mounds or hills of sand and gravel deposited by meltwater streams on or beside the glacier.
• Drumlins: Streamlined, elongated hills of till formed beneath the glacier.

The Significance of Studying Glacial Landforms

The study of glacial landforms is important for several reasons:

• Reconstructing Past Glacial Activity: Glacial landforms provide valuable evidence about the extent and behavior of past glaciers. By studying these landforms, scientists can reconstruct the history of glaciation in a particular area and learn about past climate changes.
• Understanding Landscape Evolution: Glaciers are powerful agents of landscape evolution. By studying glacial processes and landforms, we can gain a better understanding of how landscapes have been shaped over time.
• Assessing Natural Hazards: Glacial environments are often subject to natural hazards, such as glacial lake outburst floods (GLOFs) and landslides. By understanding glacial processes and landforms, we can better assess and mitigate these hazards.
• Water Resource Management: Glaciers are an important source of freshwater for many regions. By studying glaciers, we can better understand their role in the hydrological cycle and manage water resources more effectively.
• Climate Change Impacts: Glaciers are highly sensitive to climate change. They are melting at an accelerating rate in many parts of the world, providing clear evidence of global warming. By studying glaciers, we can monitor the impacts of climate change and develop strategies to adapt to these changes.

Investigating Glacial Landforms: Activity Examples

Understanding the concepts is one thing, but seeing them in action (or recognizing their remnants) is key. Here are some activity examples, categorized for different learning environments:

A. Field-Based Activities (If accessible):

These activities require access to a glaciated or formerly glaciated area.

1. Moraine Mapping:

   • Objective: Identify and map different types of moraines (lateral, medial, terminal, ground) in a glacial valley.
   • Materials: Topographic maps, GPS device or smartphone with GPS capabilities, compass, measuring tape, field notebook, pencils, camera.
   • Procedure:
     • Divide students into groups.
     • Provide each group with a topographic map of the area and instruct them to identify potential moraine locations based on the map's contour lines and landform patterns.
     • Using GPS devices, navigate to the identified locations and examine the ground for evidence of moraines (e.g., unsorted sediment, ridges).
     • Measure the height and width of the moraines using measuring tapes.
     • Record observations in field notebooks, including descriptions of the sediment, vegetation cover, and surrounding landscape.
     • Take photographs of the moraines.
     • Using the collected data, create a map of the moraines, labeling their types and dimensions.
     • Discuss the implications of the moraine distribution for understanding past glacial extent and retreat.

2. Glacial Striation Analysis:

   • Objective: Measure and analyze glacial striations to determine the direction of past ice flow.
   • Materials: Compass, geological hammer, magnifying glass, hydrochloric acid (for identifying rock types), field notebook, pencils, camera.
   • Procedure:
     • Locate exposed bedrock surfaces in the study area.
     • Carefully examine the bedrock for glacial striations (scratches and grooves).
     • Use a compass to measure the orientation (azimuth) of the striations. Take multiple measurements at different locations to account for variations.
     • Record the measurements in a field notebook.
     • Use a geological hammer to collect small rock samples for identification.
     • Examine the rock samples with a magnifying glass and test them with hydrochloric acid to determine their rock type.
     • Analyze the striation data to determine the dominant direction of ice flow.
     • Discuss the implications of the ice flow direction for understanding past glacial dynamics and landscape evolution.

3. Sediment Analysis of Glacial Deposits:

   • Objective: Collect and analyze sediment samples from different glacial deposits (e.g., moraines, outwash plains) to determine their characteristics and origin.
   • Materials: Shovels, sample bags, sieves, measuring cylinders, water, drying oven, balance, field notebook, pencils, camera.
   • Procedure:
     • Collect sediment samples from different glacial deposits.
     • Label each sample with its location and type of deposit.
     • In the lab, dry the samples in a drying oven.
     • Sieve the samples to separate the different particle sizes (e.g., gravel, sand, silt, clay).
     • Measure the mass of each particle size fraction using a balance.
     • Calculate the percentage of each particle size fraction in each sample.
     • Analyze the data to determine the characteristics of the sediment in each type of deposit.
     • Discuss the implications of the sediment characteristics for understanding the processes that formed the deposits.

B. Lab-Based/Classroom Activities:

These can be done regardless of geographical location, using models, maps, and data analysis.

1. Topographic Map Analysis of Glaciated Landscapes:

   • Objective: Identify and interpret glacial landforms on topographic maps.
   • Materials: Topographic maps of glaciated areas, colored pencils, rulers, calculators.
   • Procedure:
     • Provide students with topographic maps of glaciated areas.
     • Instruct them to identify glacial landforms, such as cirques, arêtes, horns, U-shaped valleys, hanging valleys, moraines, and outwash plains, based on the contour lines and landform patterns.
     • Use colored pencils to outline and label the identified landforms.
     • Measure the dimensions of the landforms using rulers and calculators.
     • Calculate the slopes of the valleys and ridges.
     • Discuss the implications of the landform patterns for understanding past glacial activity and landscape evolution.

2. Glacier Flow Modeling:

   • Objective: Create a physical model to demonstrate how glaciers flow and erode the landscape.
   • Materials: Sand, plaster of Paris, water, containers, food coloring, popsicle sticks.
   • Procedure:
     • Mix sand and plaster of Paris to create a model landscape.
     • Pour water over the landscape to simulate a glacier.
     • Add food coloring to the water to make the glacier more visible.
     • Use popsicle sticks to manipulate the glacier and simulate its flow.
     • Observe how the glacier erodes the landscape and creates glacial landforms.
     • Discuss the processes of glacial erosion and deposition.

3. Virtual Field Trip to a Glaciated Area:

   • Objective: Explore a glaciated area using online resources such as Google Earth, virtual reality tours, and online databases of glacial landforms.
   • Materials: Computers with internet access, Google Earth or other virtual globe software, virtual reality headsets (optional).
   • Procedure:
     • Provide students with links to online resources of glaciated areas.
     • Instruct them to explore the areas using Google Earth or other virtual globe software.
     • Identify and describe glacial landforms.
     • Research the history of glaciation in the area.
     • Discuss the impacts of glaciers on the landscape and environment.

4. Data Analysis of Glacier Mass Balance:

   • Objective: Analyze data on glacier mass balance to understand the effects of climate change on glaciers.
   • Materials: Data on glacier mass balance (available from the World Glacier Monitoring Service), spreadsheets, graphing software, calculators.
   • Procedure:
     • Provide students with data on glacier mass balance for different glaciers around the world.
     • Instruct them to create graphs of the data.
     • Calculate the trends in glacier mass balance over time.
     • Discuss the implications of the trends for understanding the effects of climate change on glaciers.

C. Creative Activities

1. Glacial Landform Diorama: Construct a diorama showcasing various glacial landforms, using materials like clay, sand, paint, and small figurines. This activity fosters spatial reasoning and artistic expression.

2. Glacier Storytelling: Write a story or create a comic strip from the perspective of a glacier or a rock being transported by a glacier. This encourages imaginative thinking and reinforces understanding of glacial processes.

D. Technology-Based Activities:

1. GIS Mapping of Glacial Features: Using GIS software, students can map and analyze glacial landforms, overlaying data layers like satellite imagery and elevation models.

2. Glacier Simulation Software: Utilize glacier simulation software to model glacier flow, erosion, and response to climate change scenarios.

FAQ about Mountain Glaciers and Glacial Landforms

• What is the difference between a glacier and an ice sheet?
  • A glacier is a mass of ice that flows downhill under its own weight, while an ice sheet is a much larger mass of ice that covers a vast area of land. Ice sheets are typically continental in scale, while glaciers are smaller and confined to mountainous regions or valleys.
• How fast do glaciers move?
  • The speed of glacier movement varies depending on several factors, including the size of the glacier, the slope of the land, the temperature of the ice, and the amount of meltwater present. Some glaciers move only a few centimeters per day, while others can move several meters per day.
• What causes glaciers to melt?
  • Glaciers melt when the rate of melting exceeds the rate of accumulation of snow and ice. This can be caused by a variety of factors, including rising temperatures, changes in precipitation patterns, and changes in solar radiation.
• What are the consequences of glacier melting?
  • Glacier melting can have a variety of consequences, including rising sea levels, changes in water availability, increased risk of glacial lake outburst floods, and changes in ecosystems.
• Can glaciers be saved?
  • While it is impossible to completely reverse the effects of climate change on glaciers, there are some things that can be done to slow down the rate of melting. These include reducing greenhouse gas emissions, protecting forests, and implementing water management strategies.

Conclusion

Mountain glaciers are dynamic and powerful forces shaping our planet's landscapes. By understanding the processes of glacial erosion, transportation, and deposition, and by studying the distinctive landforms they create, we can gain valuable insights into Earth's past, present, and future. Moreover, the study of mountain glaciers highlights the profound impacts of climate change and the urgent need for sustainable practices to protect these fragile environments for generations to come. Whether through field investigations, lab experiments, or creative projects, exploring the world of mountain glaciers offers a rich and rewarding educational experience.