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What Is Glaciation?

Michael Smathers
Michael Smathers

In the scientific community, the planet Earth is commonly understood to undergo periodic climate changes, with fluctuating temperature levels. Records of these changes can be found in the geological strata of Earth and in the chemical signatures of fossilized remains. Glaciation is the result of lowered temperatures around the planet; specifically, the movement and activity of glaciers. These are expanding ice sheets created by an accumulation of snowfall that does not have time or opportunity to melt. The existence of glaciers profoundly affects the long-term climate trends of the planet; glaciers are also responsible for land formation, such as carving out valleys and other types of erosion.

Glaciers typically form at high altitudes above the snow line, where temperatures are low enough that snow is permanent. The force of gravity carries them down mountainsides, and they are lubricated by melted water at the lowest levels of the glacier; pressure decreases the melting point of ice. Also, glaciers expand when snow falls onto them and freezes into ice. Throughout the course of a day, parts of the glacier that are at the threshold of melting will pick up and move parts of the surrounding earth. In this way, glaciation causes sediment and materials to be relocated; they are frozen to the glacier and deposited elsewhere when the ice melts.

The activity and movement of glaciers is part of glaciation.
The activity and movement of glaciers is part of glaciation.

Glaciation is one of the causes of large-scale land alteration. Erosion is the primary example of this; glaciers cause erosion in three ways: plucking, abrasion and freeze-thaw. Glacial plucking occurs when a glacier moves down a slope and the motion of the ice pulls already-fractured rock away. Abrasion is caused by rock attached to a glacier as it moves; the friction between the moving rock and underlying bedrock causes erosion of the bedrock, and this is the way most valleys are created. Freeze-thaw, meanwhile, occurs when melted water seeps into cracks in rock, where falling temperatures cause it to freeze and expand, widening the cracks.

Glaciers most commonly form at high altitudes above the snow line.
Glaciers most commonly form at high altitudes above the snow line.

Periods of glaciation occur with the Milankovitch cycles, or the variations in Earth's orbit around the sun over a period of 100,000 years. For example, obliquity, or the angle of the axial tilt, varies between 21.5 and 24.5 degrees, and this alters the amount of heat the polar ice caps receive. A smaller angle means less heat hits the poles and allows glaciers to form, and the reverse is true as well. Eccentricity, caused by the gravitational pull of Jupiter and Saturn, causes Earth's orbit to become more elliptical and therefore farther from the sun, resulting in cooler temperatures. Precession, or the rotation of the Earth's axis, alters the orientation of Earth relative to the sun and other planets.

Frequently Asked Questions

What is glaciation?

Glaciation refers to the process and period during which large areas of the Earth's surface are covered with ice sheets or glaciers. It involves the accumulation, compaction, and recrystallization of snow, which transforms into ice masses that move under their own weight. Glaciation shapes landscapes through erosion and deposition, creating features like valleys, fjords, and moraines.

How do glaciers form?

Glaciers form in regions where the accumulation of snow exceeds its melt over many years. This surplus snow compacts and recrystallizes into ice due to the pressure of overlying snow layers. Over time, as the ice mass grows, it begins to move under gravity, creating a glacier. This process can take tens to hundreds of years, depending on climate conditions.

What are the different types of glaciation?

There are two main types of glaciation: alpine and continental. Alpine glaciation occurs in mountainous regions, carving out landscapes and forming sharp peaks and valleys. Continental glaciation, on the other hand, covers vast land areas and is exemplified by the ice sheets found in Antarctica and Greenland, which together hold about 99% of the world's freshwater ice, according to the National Snow and Ice Data Center.

What are the effects of glaciation on the landscape?

Glaciation dramatically transforms landscapes through processes like plucking and abrasion. Glaciers carve out U-shaped valleys, fjords, and cirques, deposit till and create moraines. They also influence the formation of drumlins and eskers. The sheer force of moving ice sculpts the Earth's surface, leaving behind a unique topography once they retreat.

How does glaciation affect global climate?

Glaciation has a significant impact on global climate by altering Earth's albedo, or the reflectivity of its surface. Large ice sheets reflect more sunlight, leading to cooling. Additionally, glaciation affects ocean currents and atmospheric circulation patterns, which can lead to further cooling or warming in different regions. These changes can have a cascading effect on global weather patterns.

What evidence do scientists use to study past glaciations?

Scientists study past glaciations using various methods, including analyzing ice cores, sediment layers, and landforms. Ice cores provide a detailed record of past climate conditions, preserving bubbles of ancient air. Sediment layers offer insights into historical sea levels and temperatures. Landforms, such as moraines and striations on rocks, indicate the presence and movement of glaciers in the geological past.

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    • The activity and movement of glaciers is part of glaciation.
      By: elnavegante
      The activity and movement of glaciers is part of glaciation.
    • Glaciers most commonly form at high altitudes above the snow line.
      By: Kotangens
      Glaciers most commonly form at high altitudes above the snow line.