Glaciation
Glaciation refers to the alteration of the Earth's surface through the processes of erosion and deposition caused by glacier ice. Glaciers, which form above the snow line, begin as compacted snow that evolves into dense glacial ice under pressure. As glaciers grow thick enough, they start to flow, eroding the landscape and creating distinct U-shaped valleys, cirques, and arêtes. This glacial activity shapes the Earth significantly, leaving behind various landforms such as moraines and drumlins, as well as erratics—large boulders transported over distances. The meltwater from glaciers provides vital fresh water and contributes to hydroelectric power generation in some regions. Additionally, glaciation enriches agricultural soils through the creation of loess, a fine mineral-rich dust. Overall, glaciation not only influences climate and geography but also offers significant economic benefits through its impact on natural resources.
On this Page
Subject Terms
Glaciation
CATEGORY: Geological processes and formations
Glaciation is the effect of glaciers on the Earth’s surface, including erosion and the deposition of glaciated materials. Glaciers are related to a number of natural resources, helping to provide fresh water, rich soils, and deposits used for building materials.
Definition
The American Geological Institute’s Dictionary of Geological Terms defines glaciation as the “alteration of the Earth’s solid surface through and by ice.” As much as 75 percent of Earth’s is tied up in the form of glaciers and ice caps. Glaciation has a profound effect on (as does climate on glaciation), and glaciers have important economic benefits. For example, water melted from glaciers is an important source of fresh water.
Overview
Glaciers begin above the snow line. Snow becomes compacted into granules, and as additional snow is added, weight and pressure lead to recrystallization in the form of dense glacial ice. Once the ice reaches sufficient thickness, the internal strength of the crystals is overcome by the weight of the ice, and the ice begins to flow in the form of a glacier. Glaciers can flow by internal deformation only, or by deformation in combination with basal sliding on a thin layer of meltwater. As glaciers flow, they erode the surface of the Earth, scouring it and plucking up boulders large and small. Glaciated valleys are distinctly U-shaped, as contrasted with the typical V shape of river valleys.
Glacial scouring can create a number of landforms. These include small, steep-sided valleys called cirques and sharp ridges called arêtes. Three or more cirque valleys can leave land in a recognizable horn shape, such as the famous Matterhorn in the Pennine Alps. Smaller glaciers feed larger glaciers much the same way that small rivers feed larger ones. Since the depth of scour is proportional to the mass of the glacier, smaller tributaries can leave forms known as hanging valleys isolated more than 100 meters above a steep-sided main valley.
Rock and boulders pushed or carried along by a glacier form moraines, drumlins, and glacial till. As glaciers retreat, they leave their burden of behind. Erratics, boulders that have been carried great distances and then left behind as glaciers retreat, have been used since prehistoric times as construction material for homes and fences. Meltwater from glaciers can sort transported sand and gravel, forming long sinuous eskers and landforms called kames. The finely graded sand and gravel is an important source of for the construction industry.
In some northern countries, meltwater from glaciers not only is used as a source of fresh water but also—where there is sufficient height and volume—can be used to generate hydroelectric power. Glaciation has other important economic benefits. The scouring effect of glaciers creates a fine dust-sized material called loess. Wind eventually transports and deposits the mineral-rich loess, helping to create some of the richest agricultural soils in the world.
"Glacier." National Geographic, 4 Dec. 2024, education.nationalgeographic.org/resource/glacier/. Accessed 27 Dec. 2024.
"Glaciers: Moving Rivers of Ice." National Geographic, 19 Oct. 2023, education.nationalgeographic.org/resource/glacier-moving-rivers-ice/. Accessed 27 Dec. 2024.
"What Is a Glacier?" USGS, www.usgs.gov/faqs/what-glacier. Accessed 27 Dec. 2024.