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Table of Contents
A glacier is an enduring body of thick ice that moves under its weight. A glacier formed when the accumulation of snow over many years, perhaps millennia, surpasses its ablation. As it slowly flows and deforms under the strains caused by its weight, it develops unique characteristics such as crevasses and seracs. It moves, abrading rock and debris from its substrate to generate landforms like cirques, moraines, and fjords. A glacier may float into a body of water, but it forms solely on land, as opposed to the much thinner sea ice and lake ice that develops on the surface of bodies of water.
See the fact file below for more information about Glacier, or download the comprehensive worksheet pack, which contains over 11 worksheets and can be used in the classroom or homeschooling environment.
Key Facts & Information
ETYMOLOGY
- The term glacier is a foreign word from French and may be traced back to the Vulgar Latin via Franco-Provençal.
- Latin glacirium, from Late Latin glacia, and Latin glacis, meaning “ice.”
- Glacial processes and characteristics are those induced or influenced by glaciers. Glaciation is the process of glacier formation, development, and flow.
- Glaciology is a comparable field of study, and glaciers play a vital role in the global cryosphere.
CLASSIFICATION: SIZE, SHAPES, AND BEHAVIOR
- Glaciers are classified based on their form, thermal properties, and behavior. Alpine glaciers grow on mountain crests and slopes. Valley glaciers, also known as alpine glacier, is a glacier that fills a valley. An ice cap or field is a vast body of glacial ice that sits atop a mountain range or volcano.
- Ice caps cover less than 50,000 km2 (19,000 sq mi). Ice sheets or continental glaciers are glacial masses greater than 50,000 km2 (19,000 sq mi). They are many kilometers deep and hide the underlying landscape. Nunataks are the only things that protrude from their surfaces. The only remaining ice sheets are those that cover the majority of Antarctica and Greenland.
- They hold so much freshwater that if both dissolved, global sea levels would increase by more than 70 meters (230 ft). Ice shelves are pieces of an ice sheet or cap that extend into the ocean; they are typically narrow, with restricted slopes and velocities. Ice streams are limited, fast-moving parts of an ice sheet.
- Many ice streams in Antarctica flow onto enormous ice shelves. Some, like Mertz Glacier, drain directly into the sea, frequently with an ice tongue.
- Many glaciers moving from Greenland, Antarctica, Baffin, Devon, and Ellesmere Islands in Canada, Southeast Alaska, and the Northern and Southern Patagonian Ice Fields are tidewater glaciers.
- As the ice hits the sea, parts break off or calve, forming icebergs. Most tidewater glaciers calve above sea level, resulting in a massive impact as the iceberg strikes the water. Tidewater glaciers rise and retreat through centuries-long cycles that are far less impacted by climate change than other glaciers.
CLASSIFICATION: THERMAL STATE
- A temperate glacier melts throughout the year, from its surface to its base. Polar glacier ice is constantly below the freezing point from the surface to the bottom, while the surface snowpack may melt seasonally.
- A subpolar glacier contains both temperate and polar ice, depending on its depth under the surface and location along its length. Similarly, a glacier’s thermal regime is frequently defined by its basal temperature.
- A cold-based glacier has an ice-ground contact below freezing and is frozen to the underlying substrate.
- A warm-based glacier is above or near freezing at the interface and can slide there. This disparity is assumed to regulate a glacier’s capacity to successfully erode its bed since moving ice encourages tugging at the rock from the surface below.
- Polythermal glaciers are those that are partially cold and partly warm.
FORMATION
- Glaciers arise when snow and ice buildup surpass ablation.
- A glacier is frequently formed by a cirque landform (also known as a “corrie” or a “cwm”), which is a characteristically armchair-shaped geological feature (such as a dip between mountains enclosed by arêtes) that accumulates and compresses the snow that falls into it by gravity.
- This snow collects, and the weight of the snow falling compacts above it, resulting in the formation of névé (powdery snow).
- Crushing the tiny snowflakes and squeezing the air out of the snow further transforms it into “glacial ice.” This glacial ice will cover the cirque until it “overflows” via a geological void or weakness, such as a breach between two mountains. When a pile of snow and ice becomes thick enough, it starts to move due to various surface slopes, gravity, and pressure.
- It can happen on steeper slopes with as little as 15 m (50 ft) of snow-ice. Snow continually freezes and thaws in temperate glaciers, transforming into granular ice known as firn. This fine ice combines into denser firn under the weight of the layers of ice and snow above it.
- Over time, firn layers grow more compacted and eventually turn into glacial ice. Because glacier ice has fewer trapped air bubbles, it is somewhat denser than ice created from frozen water.
- Glacial ice is blue because it collects red light due to an overtone of the water molecule‘s infrared OH stretching mode. (For the same reason, liquid water appears blue; the blue of glacier ice is frequently falsely attributed to Rayleigh’s scattering of bubbles in the ice.)
STRUCTURE
- A glacier begins at a position known as the glacier head and ends at the glacier foot, snout, or terminal.
- Glaciers are classified according to their surface snowpack and melt conditions. The ablation zone is the glacier area with a net mass loss, and the accumulation zone is the highest section of a glacier when accumulation surpasses ablation. The equilibrium line is the contour that divides the ablation zone from the accumulation zone; it is the contour where the quantity of fresh snow obtained by accumulation equals the amount of ice lost by ablation.
- In general, the buildup zone accounts for 60-70% of the glacier’s surface area, with the accumulation zone accounting for even more of the glacier calves icebergs. The accumulation zone’s ice is deep enough to impose a downward pull on the underlying rock.
- When a glacier melts, it frequently leaves behind a bowl- or amphitheater-shaped depression ranging in size from enormous basins like the Great Lakes to tiny mountain depressions known as cirques.
- Can use the melt conditions of the accumulation zone to partition it.
- The dry snow zone is characterized as a place with no melt, even during the summer, and a dry snowfall.
- The percolation zone is a region with a surface melt that allows meltwater to seep into the snowpack. This zone is frequently distinguished by refrozen ice lenses, glands, and layers. Similarly, the snowpack never reaches the melting point.
- A superimposed ice zone forms around the equilibrium line on some glaciers. Meltwater in the glacier refreezes as a cool layer, resulting in a persistent ice mass in this zone.
- The wet snow zone is where all of the snow that has fallen since the end of the previous summer has reached 0 °C.
- A glacier’s health is often determined by estimating the glacier mass balance or watching terminal activity. Healthy glaciers feature vast accumulation zones, more than 60% of their area is snow-covered after the melt season, and a vigorously flowing terminal.
- Glaciers have receded significantly since the end of the Little Ice Age, about 1850. Between 1950 and 1985, a slight cooling caused many alpine glaciers to advance, but after 1985, glacier retreat and mass loss became more significant and widespread.
MOTION
- Glaciers migrate or flow downwards due to gravity and internal ice deformation. Ice acts like a brittle solid until its thickness surpasses around 50 m (160 ft). Plastic flow is caused by pressure on ice deeper than 50 meters.
- Ice comprises stacked layers of molecules with relatively weak connections at the molecular level. The layer above moves faster than the layer below when the load on the layer above surpasses the inter-layer binding strength.
- Glaciers move with basal sliding as well. A glacier glides across the land it resides on, lubricated by the existence of liquid water. The water is formed when the ice melts under high pressure due to frictional heating. In temperate or warm-based glaciers, basal sliding is prevalent.
FRACTURE ZONE AND CRACKS
- Because of the low pressure, the glacier’s top 50 meters (160 feet) are stiff. The fracture zone is the upper part, which travels primarily as a single unit over the plastic-flowing bottom segment.
- Crevasses form in the fracture zone of a glacier when it advances across uneven terrain—variations in glacier velocity cause crevasses to develop. Shear pressure causes two stiff portions of a glacier to break apart and open a crack if they move at opposite rates or orientations.
- Crevasses are rarely more than 46 m (150 ft) deep but can be at least 300 m (1,000 ft) deep in extreme situations. The flexibility of the ice under this point prevents fissures from forming. Intersecting crevasses can form solitary ice peaks known as seracs.
SPEED
- Friction influences the pace of glacial movement, and friction causes the ice at the glacier’s bottom to move more slowly than at the glacier’s top. Friction is also formed along the valley’s sidewalls in alpine glaciers, slowing the margins relative to the center.
- The average glacial pace varies widely, although it is usually approximately 1 meter (3 feet) daily. In static locations, there may be little movement; for example, trees can sustain themselves on surface sediment deposits in portions of Alaska. Other glaciers, such as Greenland’s Jakobshavn Isbrae, can flow as quickly as 20-30 m (70-100 ft) each day.
- Slope, ice thickness, precipitation, longitudinal confinement, baseline temperature, meltwater production, and bed hardness all influence glacial pace.
- Surges are episodes of swift progress on a few glaciers. These glaciers typically travel until they suddenly accelerate and then revert to their former movement condition.
- The breakdown of the underlying bedrock might trigger these surges, the pooling of meltwater at the glacier’s base — possibly delivered from a supraglacial lake — or simply the accumulation of mass beyond a crucial “tipping point.”
OGIVES
- Ogives (or Forbes bands) are recurring wave crests and troughs that show on glacier surfaces as dark and light ice bands. They are related to seasonal glacier motion; the breadth of one dark and one bright band roughly reflects the glacier’s yearly movement.
- When ice from an icefall is badly broken up, it increases the ablation surface area throughout the summer. It provides a swale and room for snow accumulation in the winter, leading to a ridge formation. Ogives merely undulations or color bands are called wave ogives or band ogives.
CLIMATE CHANGE
- Glaciers are essential for detecting long-term climate change since they can be hundreds of thousands of years old.
- Ice cores are extracted to investigate the patterns throughout time in glaciers, giving frequent feedback, including evidence for climate change stored in the ice for scientists to break down and analyze. Glaciers are examined to understand the history of climate change caused by natural or human factors.
- Human activity has generated a rise in greenhouse gases, resulting in global warming and the melting of these crucial glaciers. Glaciers have an albedo impact, and melting glaciers result in reduced albedo. Compared to the summer of 2003 in the Alps to the summer of 1988, the albedo value in 2003 was 0.2 lower than in 1998.
- When glaciers melt, sea levels rise, “which increases coastal erosion and boosts storm surge as warmer air and ocean temperatures generate more frequent and stronger coastal storms like hurricanes and typhoons.”
- Thus, human-caused climate change generates a positive feedback loop with glaciers: rising temperatures drive more glacier melt, resulting in less albedo, higher sea levels, and a slew of other climatic challenges.
- NASA has employed a Landsat satellite to record glaciers in Alaska, Greenland, and Antarctica since 1972 and will persist until 2019. This Landsat project discovered that glacier retreat had risen significantly since roughly 2000.
Glacier Worksheets
This bundle contains 11 ready-to-use Glacier Worksheets that are perfect for students who want to learn more about a Glacier, which is an enduring body of thick ice that moves under its weight and forms when the accumulation of snow over many years, perhaps millennia, surpasses its ablation.
Download includes the following worksheets:
- Glacier Facts
- Glacier Sketch
- Glacier Yes Or No
- Glacier Acrostic Poem
- Glacier Formation
- Glacier Fill In The Blanks
- Spot The Glaciers
- Animals In Glaciers
- All About The Titanic
- Glacier News Report
- Glacier Word Search
Frequently Asked Questions
What is a glacier?
A glacier is an enduring body of thick ice that moves under its weight.
How does a glacier get its name?
The term glacier is a foreign word from French and may be traced back to the Vulgar Latin via Franco-Provençal. Latin glacirium, from Late Latin glacia, and Latin glacis, meaning “ice.”
How does glacier forms?
A glacier is frequently formed by a cirque landform (also known as a “corrie” or a “cwm”), which is a characteristically armchair-shaped geological feature (such as a dip between mountains enclosed by arêtes) that accumulates and compresses the snow that falls into it by gravity.
Why is glacier ice blue?
Glacial ice is blue because it collects red light due to an overtone of the water molecule’s infrared OH stretching mode.
How does climate change affect glaciers?
When glaciers melt, sea levels rise, “which increases coastal erosion and boosts storm surge as warmer air and ocean temperatures generate more frequent and stronger coastal storms like hurricanes and typhoons.” Thus, human-caused climate change generates a positive feedback loop with glaciers: rising temperatures drive more glacier melt, resulting in less albedo, higher sea levels, and a slew of other climatic challenges.
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Link will appear as Glacier Facts & Worksheets: https://kidskonnect.com - KidsKonnect, October 26, 2017
Use With Any Curriculum
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