An overview of glaciers
Glaciers are a hot topic these days and are a frequent subject of debate when discussing global climate change or the fate of polar bears. Do you ever find yourself asking what glaciers have to do with global warming? Have you ever wondered what exactly your friend meant when she told you that you moved at a glacial pace? Either way, read on, and learn all about these frozen landforms.
Glacier basics
A glacier is essentially a huge mass of ice resting on land or floating in the sea next to land. Moving extremely slowly, a glacier acts similarly to an immense river of ice, often merging with other glaciers in a stream-like manner.
Regions with continuous snowfall and constant freezing temperatures foster the development of these frozen rivers. It is so cold in these regions that when a snowflake hits the ground it does not melt, but instead combines with other snowflakes to form larger grains of ice. As more and more snow accumulates, mounting weight and pressure squeeze these grains of ice together to form a glacier.
A glacier cannot form unless is it above the snowline, the lowest elevation at which snow can survive year round. Most glaciers form in high mountain regions such as the Himalayas of Southern Asia or the Alps of Western Europe where regular snow and extremely cold temperatures are present. Glaciers are also found in Antarctica, Greenland, Iceland, Canada, Alaska, and even South America (the Andes), California (the Sierra Nevada), and Mount Kilimanjaro in Tanzania.
As tiny air bubbles are eventually forced out by the increasing pressure the glacier appears blue, a sign of highly dense, airless ice.
Glaciers may be retreating worldwide due to global warming, but they still cover about 10% of earth’s land and hold about 77% of earth’s freshwater (29,180,000 cubic kilometers).
Types of glaciers
Glaciers can be characterized in two ways based on their formation: alpine and continental.
Alpine Glacier - Most glaciers that form in a mountain are known as alpine glaciers. There are several subtypes of alpine glaciers:
Cirque: a cirque is a bowl shaped hollow at the head of a valley. Within a cirque lies a snowfield, the place where snow accumulates to form a cirque glacier.
Valley: any glacier that resides in an area eroded by stream action is called a valley glacier. These types of glaciers tend to be very long and often times pass below the snowline.
Piedmont: when multiple valley glaciers come together as one at a large stretch of flat line, the resulting mass is a piedmont glacier.
Tidewater: a glacier that meets the sea is known as a tidewater glacier. Usually a process called calving occurs, when a piece of the glacier breaks off in to the sea, forming a large mass of floating ice known as an iceberg.
Continental Glacier – An expansive, continuous mass of ice considerably bigger than an alpine glacier is known as a continental glacier. There are three primary subtypes:
Ice Sheet: the largest of any glacier type, extending over 50,000 square kilometers. The only places on earth that have these frozen monsters are Antarctica and Greenland. Antarctica alone is home to 92% of all glacial ice worldwide. Ice sheets are so massive and heavy that they literally bend the continental crust on which they sit, a phenomena known as isostatic depression.
Ice Cap: similar to an ice sheet, though smaller and forming a roughly circular, dome-like structure that completely blankets the landscape underneath.
Ice Field: a smaller version on an ice cap that fails to cover the land and is elongated relative to the underlying topography.
Glacial Movement
There are two types of glacial movement: sliders and creepers. Sliders travel along a thin film of water located on the bottom of the glacier. Creepers, on the other hand, form internal layers of ice crystals that move past one another based on the surrounding conditions (e.g. weight, pressure, temperature). The top and middle layers of a glacier tend to move faster than the rest. Most glaciers are both creepers and sliders, plodding along in both fashions.
Glacier speed can vary from virtually at rest to a kilometer or more per year. On average, though, glaciers move at the laggardly pace of a couple hundred feet per year. In general, a heavier glacier moves quicker than a lighter one, a steep glacier quicker than a less steep one, a warmer glacier quicker than a cooler one.
Image source

An overview of glaciers

Glaciers are a hot topic these days and are a frequent subject of debate when discussing global climate change or the fate of polar bears. Do you ever find yourself asking what glaciers have to do with global warming? Have you ever wondered what exactly your friend meant when she told you that you moved at a glacial pace? Either way, read on, and learn all about these frozen landforms.

Glacier basics

A glacier is essentially a huge mass of ice resting on land or floating in the sea next to land. Moving extremely slowly, a glacier acts similarly to an immense river of ice, often merging with other glaciers in a stream-like manner.

Regions with continuous snowfall and constant freezing temperatures foster the development of these frozen rivers. It is so cold in these regions that when a snowflake hits the ground it does not melt, but instead combines with other snowflakes to form larger grains of ice. As more and more snow accumulates, mounting weight and pressure squeeze these grains of ice together to form a glacier.

A glacier cannot form unless is it above the snowline, the lowest elevation at which snow can survive year round. Most glaciers form in high mountain regions such as the Himalayas of Southern Asia or the Alps of Western Europe where regular snow and extremely cold temperatures are present. Glaciers are also found in Antarctica, Greenland, Iceland, Canada, Alaska, and even South America (the Andes), California (the Sierra Nevada), and Mount Kilimanjaro in Tanzania.

As tiny air bubbles are eventually forced out by the increasing pressure the glacier appears blue, a sign of highly dense, airless ice.

Glaciers may be retreating worldwide due to global warming, but they still cover about 10% of earth’s land and hold about 77% of earth’s freshwater (29,180,000 cubic kilometers).

Types of glaciers

Glaciers can be characterized in two ways based on their formation: alpine and continental.

Alpine Glacier - Most glaciers that form in a mountain are known as alpine glaciers. There are several subtypes of alpine glaciers:

  • Cirque: a cirque is a bowl shaped hollow at the head of a valley. Within a cirque lies a snowfield, the place where snow accumulates to form a cirque glacier.
  • Valley: any glacier that resides in an area eroded by stream action is called a valley glacier. These types of glaciers tend to be very long and often times pass below the snowline.
  • Piedmont: when multiple valley glaciers come together as one at a large stretch of flat line, the resulting mass is a piedmont glacier.
  • Tidewater: a glacier that meets the sea is known as a tidewater glacier. Usually a process called calving occurs, when a piece of the glacier breaks off in to the sea, forming a large mass of floating ice known as an iceberg.

Continental Glacier – An expansive, continuous mass of ice considerably bigger than an alpine glacier is known as a continental glacier. There are three primary subtypes:

  • Ice Sheet: the largest of any glacier type, extending over 50,000 square kilometers. The only places on earth that have these frozen monsters are Antarctica and Greenland. Antarctica alone is home to 92% of all glacial ice worldwide. Ice sheets are so massive and heavy that they literally bend the continental crust on which they sit, a phenomena known as isostatic depression.
  • Ice Cap: similar to an ice sheet, though smaller and forming a roughly circular, dome-like structure that completely blankets the landscape underneath.
  • Ice Field: a smaller version on an ice cap that fails to cover the land and is elongated relative to the underlying topography.

Glacial Movement

There are two types of glacial movement: sliders and creepers. Sliders travel along a thin film of water located on the bottom of the glacier. Creepers, on the other hand, form internal layers of ice crystals that move past one another based on the surrounding conditions (e.g. weight, pressure, temperature). The top and middle layers of a glacier tend to move faster than the rest. Most glaciers are both creepers and sliders, plodding along in both fashions.

Glacier speed can vary from virtually at rest to a kilometer or more per year. On average, though, glaciers move at the laggardly pace of a couple hundred feet per year. In general, a heavier glacier moves quicker than a lighter one, a steep glacier quicker than a less steep one, a warmer glacier quicker than a cooler one.

Image source

(Source: geography.about.com)

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    Great information on glaciers.
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