What Are Two Kinds Of Glaciers

Glaciers, those majestic rivers of ice, are not all created equal. They come in various shapes and sizes, each molded by unique environmental conditions. Understanding the different types of glaciers helps us appreciate their diversity and how they respond to climate change. In this article, we'll delve into two primary classifications of glaciers: alpine glaciers and ice sheets, exploring their characteristics, formation, and significance.

Alpine Glaciers: Sculptors of Mountain Landscapes

Alpine glaciers, also known as mountain or valley glaciers, are precisely what their name suggests: glaciers formed in mountainous regions. They are often found in narrow valleys, flowing downhill under the force of gravity. These glaciers are responsible for carving out some of the most dramatic and stunning landscapes on Earth.

Formation of Alpine Glaciers

The formation of an alpine glacier is a gradual process that requires specific conditions:

• Accumulation of Snow: The process begins with snowfall. In high-altitude regions, where temperatures are consistently low, snow accumulates over time.
• Compaction and Firn Formation: As more snow falls, the weight of the overlying layers compresses the snow beneath. This compression forces out air and causes the snowflakes to transform into rounded ice grains called firn.
• Glacier Ice Formation: Over years and decades, the firn continues to compact, eventually forming dense, crystalline glacier ice. This ice is distinct from regular ice, as it is incredibly dense and strong.
• Glacier Movement: Once the ice mass reaches a sufficient thickness, typically around 50 meters, it begins to flow downhill under the influence of gravity. The movement is slow but relentless, shaping the landscape as it advances.

Types of Alpine Glaciers

Alpine glaciers can be further classified based on their size, shape, and relationship to the surrounding terrain:

• Valley Glaciers: These are the most common type of alpine glacier. They occupy existing river valleys, flowing like icy rivers between mountain ranges. Valley glaciers can be several kilometers long and hundreds of meters thick.
• Cirque Glaciers: Cirque glaciers are smaller, bowl-shaped glaciers that form in hollows on mountainsides called cirques. These cirques are often created by the erosive action of the glacier itself.
• Hanging Glaciers: These glaciers cling to steep slopes or cliffs, often appearing as if they are "hanging" precariously. They are usually smaller than valley glaciers and can be prone to icefalls.
• Piedmont Glaciers: Piedmont glaciers form when valley glaciers flow out onto a relatively flat plain at the base of a mountain range. The ice spreads out, creating a broad, fan-shaped glacier.

Features Created by Alpine Glaciers

Alpine glaciers are powerful agents of erosion, leaving behind a distinctive imprint on the landscape:

• U-Shaped Valleys: As a glacier moves down a valley, it erodes the valley walls and floor, transforming the original V-shaped river valley into a wide, U-shaped valley.
• Arêtes and Horns: When two or more cirque glaciers erode a mountain from different sides, they can create sharp, jagged ridges called arêtes. If three or more cirques erode a mountain, they can form a pointed peak called a horn. The Matterhorn in the Swiss Alps is a classic example of a horn.
• Moraines: Moraines are accumulations of rock and sediment that are transported and deposited by glaciers. There are several types of moraines:
  • Lateral Moraines: Form along the sides of a glacier.
  • Medial Moraines: Form when two glaciers merge, creating a stripe of debris down the center of the combined glacier.
  • Terminal Moraines: Form at the terminus (end) of a glacier, marking its farthest advance.
  • Ground Moraine: A layer of sediment deposited beneath the glacier as it melts.
• Striations: These are scratches or grooves on bedrock caused by rocks embedded in the base of the glacier as it moves. Striations indicate the direction of glacier flow.
• Cirques: Bowl-shaped depressions where cirque glaciers originate.
• Tarns: Lakes that form in cirques after the glacier has melted.
• Hanging Valleys: Tributary valleys that are left hanging high above the main valley after the glacier has retreated. Waterfalls often form in hanging valleys.
• Fiords: Long, narrow inlets with steep sides, formed when a glacier-carved valley is flooded by the sea.

Importance of Alpine Glaciers

Alpine glaciers are vital components of mountain ecosystems and play a crucial role in water resources:

• Water Supply: Glacial meltwater provides a reliable source of water for rivers and streams, especially during dry seasons. Many communities rely on glacial meltwater for drinking water, irrigation, and hydropower.
• Ecosystem Support: Glacial meltwater sustains unique ecosystems, supporting a variety of plant and animal life.
• Tourism and Recreation: Glaciers attract tourists and recreation enthusiasts who come to admire their beauty, hike on them, or ski in glaciated areas.

Ice Sheets: Continental-Scale Ice Masses

Ice sheets are the largest type of glacier, covering vast areas of land and containing immense volumes of ice. They are continental-scale ice masses that can be thousands of meters thick. Today, there are only two ice sheets on Earth: the Greenland Ice Sheet and the Antarctic Ice Sheet.

Formation of Ice Sheets

The formation of an ice sheet is a long and complex process that requires extremely cold temperatures and significant snowfall:

• Prolonged Cold Temperatures: Ice sheets form in regions where temperatures remain below freezing for most of the year. This allows snow to accumulate over long periods without melting.
• Massive Snow Accumulation: Over thousands of years, massive amounts of snow accumulate, compacting into firn and then into glacier ice.
• Ice Sheet Growth and Spread: As the ice sheet grows, its weight causes the ice to spread outward under its own gravity. The ice flows towards the edges of the ice sheet, where it eventually melts or calves (breaks off) into icebergs.

Characteristics of Ice Sheets

Ice sheets have several distinct characteristics:

• Vast Size: Ice sheets cover millions of square kilometers, burying entire landscapes beneath ice.
• Immense Thickness: Ice sheets can be thousands of meters thick. The Antarctic Ice Sheet, for example, is over 4,000 meters thick in some areas.
• Dome-Shaped Profile: Ice sheets typically have a dome-shaped profile, with the highest point in the center and gradually sloping edges.
• Slow Movement: While ice sheets are constantly moving, their movement is very slow, typically only a few meters per year. However, some areas, such as ice streams, can flow much faster.

Features Associated with Ice Sheets

Ice sheets create a variety of distinctive features:

• Ice Streams: These are fast-flowing rivers of ice within an ice sheet. Ice streams can transport large amounts of ice to the ocean, contributing to sea level rise.
• Ice Shelves: Ice shelves are floating extensions of an ice sheet that extend over the ocean. They are attached to the mainland ice sheet and can be hundreds of meters thick. Ice shelves play an important role in stabilizing ice sheets by buttressing the flow of ice from the land.
• Nunataks: These are isolated mountain peaks that protrude through the ice sheet. They provide valuable insights into the landscape beneath the ice.
• Eskers: Long, sinuous ridges of sediment deposited by meltwater streams flowing beneath the ice sheet.
• Kettles: Depressions in the landscape formed when buried blocks of ice melt, leaving behind a hole.
• Drumlins: Elongated hills of sediment that are aligned in the direction of ice flow.

Importance of Ice Sheets

Ice sheets play a critical role in the global climate system and have a significant impact on sea level:

• Sea Level Regulation: Ice sheets contain the vast majority of Earth's freshwater. If the Greenland and Antarctic ice sheets were to melt completely, global sea levels would rise by over 60 meters, inundating coastal cities and displacing millions of people.
• Climate Regulation: Ice sheets reflect a significant portion of incoming solar radiation back into space, helping to regulate Earth's temperature. Their high albedo (reflectivity) helps to keep the planet cool.
• Ocean Circulation: Ice sheets influence ocean circulation patterns. The melting of ice sheets adds freshwater to the ocean, which can disrupt ocean currents and affect global climate patterns.

The Critical Differences: Alpine Glaciers vs. Ice Sheets

While both alpine glaciers and ice sheets are masses of ice that flow under the force of gravity, there are key differences between them:

• Size: Ice sheets are much larger than alpine glaciers, covering vast areas of land. Alpine glaciers are typically confined to mountain valleys.
• Scale: Ice sheets are continental-scale features, while alpine glaciers are regional or local features.
• Thickness: Ice sheets are much thicker than alpine glaciers, often reaching thousands of meters in thickness.
• Formation: Ice sheets require extremely cold temperatures and massive snow accumulation over long periods. Alpine glaciers can form in mountainous regions with sufficient snowfall and cold temperatures.
• Impact: Ice sheets have a global impact on sea level and climate, while alpine glaciers have a more localized impact on water resources and ecosystems.

The Impact of Climate Change on Glaciers

Both alpine glaciers and ice sheets are highly sensitive to changes in temperature. As global temperatures rise due to climate change, glaciers are melting at an accelerating rate.

Effects on Alpine Glaciers

• Glacier Retreat: Alpine glaciers are retreating rapidly around the world. Many smaller glaciers are disappearing altogether.
• Reduced Water Availability: As glaciers shrink, the amount of meltwater available for rivers and streams decreases, leading to water shortages in some regions.
• Increased Risk of Glacial Lake Outburst Floods (GLOFs): As glaciers retreat, they can create glacial lakes dammed by unstable moraines. If these moraines fail, they can release catastrophic floods that can devastate downstream communities.

Effects on Ice Sheets

• Accelerated Melting: Ice sheets are melting at an alarming rate, particularly in Greenland and West Antarctica.
• Sea Level Rise: The melting of ice sheets is the largest contributor to global sea level rise.
• Disruption of Ocean Circulation: The influx of freshwater from melting ice sheets can disrupt ocean currents and affect global climate patterns.

The Future of Glaciers

The future of glaciers is uncertain. If global temperatures continue to rise, many alpine glaciers will disappear, and ice sheets will continue to melt at an accelerating rate. This will have profound consequences for water resources, ecosystems, and sea level.

Mitigation and Adaptation

To mitigate the impacts of climate change on glaciers, it is essential to reduce greenhouse gas emissions and transition to a low-carbon economy. In addition, we need to adapt to the changes that are already occurring, such as developing water management strategies to cope with reduced water availability and implementing early warning systems for GLOFs.

Conclusion

Glaciers are dynamic and fascinating features of our planet. Understanding the different types of glaciers – alpine glaciers and ice sheets – helps us appreciate their diversity and the critical role they play in the Earth's climate system. As climate change continues to impact our world, it is more important than ever to study and protect these vital resources. Their fate is inextricably linked to our own. By taking action to reduce greenhouse gas emissions and adapt to the changing climate, we can help preserve these magnificent landscapes for future generations.