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How do Glaciers Move?

Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov

Glaciers are gigantic, solid “rivers” of ice. They have been around for much of earth’s history, and are responsible for large geographic features on its surface, including the Great Lakes. Glaciers travel miles from their point of origin and deposit debris in wide swaths of land.

The question is, how does a solid like ice move like that? There are rockslides, but they are sudden and caused merely by erosion. Rockslides do not flow for miles in the way that glaciers do. So what is the cause of this glacial motion?

Pressure and temperature variations help determine how glaciers move.
Pressure and temperature variations help determine how glaciers move.

There are several mechanisms at play. The primary one has to do with the relationship between temperature and pressure. The melting point of most substances increases as the pressure increases – atoms pushed more closely together become more stable. This is not the case with ice. For ice, the melting point drops as pressure increases.

The ice at the bottom of glaciers is under enormous pressure. Some glaciers are over a mile deep. Through a combination of these extreme pressures and latent heat coming from the earth itself, some of the ice melts and gives the glacier above it a slick surface to slide down.

However, this melting process is not reliable. It varies depending on pressure and temperature variations. Therefore, glaciers only move slowly, between an inch and a couple of feet per day. The large variance in glaciers' flow speeds is due to the equally large variance in pressures and temperatures within the glacier.

Another mechanism is motions of the ice crystals within the glacier itself. A glacier is faster at its center, where there is the least friction with surrounding rock. Little ice particles, even in solid form, move tiny millionths of an inch in response to slight pressure changes and small inclines. The aggregate influence of all these little motions adds up to a significant global effect that propels the glacier forward.

Sometimes, glaciers move forward at an unprecedented pace, called a surge. For instance, in 1953, the Himalayan Kutiah Glacier moved seven miles in three months. Scientists are still not entirely sure of the cause of these surges, but they may occur when delicate structural arrangements within the glacier reach a “tipping point” and cause a cascade of collapses and a corresponding flow.

Frequently Asked Questions

What causes glaciers to move?

Glaciers move due to gravity and the immense weight of accumulated ice. As layers of snow compact into ice over time, the glacier's mass increases, creating pressure that deforms the ice and causes it to flow. This movement can be internal, where the ice deforms within itself, or basal sliding, where the glacier slides over the ground beneath it.

How fast do glaciers move?

The speed of glacier movement varies widely, from a few centimeters to several meters per day. Fast-moving glaciers, known as galloping glaciers, can advance more than 30 meters daily. However, most glaciers move at a much slower pace. The rate of movement is influenced by factors such as ice thickness, slope steepness, and the presence of meltwater at the base.

Can the movement of glaciers be influenced by climate change?

Yes, climate change significantly impacts glacier movement. Warmer temperatures can increase meltwater production, which may lubricate the glacier base and accelerate its slide over the bedrock. Conversely, higher temperatures can also lead to increased ice melt and reduced glacier mass, potentially slowing down movement due to less gravitational force.

What are the effects of glacier movement on the landscape?

Glacier movement profoundly shapes the landscape through processes like erosion and deposition. As glaciers advance, they can carve valleys, form fjords, and create moraines by pushing debris ahead of them. When they retreat, they often leave behind a sculpted terrain, with features such as U-shaped valleys, drumlins, and kettle lakes.

What is the difference between ice flow and ice surge?

Ice flow refers to the regular movement of a glacier, which is typically slow and steady. An ice surge, however, is a short-lived event where a glacier can move tens to hundreds of meters per day, significantly faster than its usual pace. Surges can occur due to various reasons, including the build-up of water pressure beneath the glacier.

How are glacier movements monitored?

Glacier movements are monitored using a combination of satellite imagery, GPS, and on-site measurements. These methods allow scientists to track changes in glacier position, velocity, and thickness over time. Monitoring is crucial for understanding glacier dynamics, predicting future changes, and assessing the potential impact on sea-level rise and water resources.

Michael Anissimov
Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...
Michael Anissimov
Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...

Discussion Comments

Babalaas

@ Alchemy - You described the movement of glaciers across the bedrock, but glacial movement can also be examined as a natural force much like the ebb and flow of the tides. In this context glacial movement is referred to in terms of accumulation and ablation.

Accumulation is the addition of snow that turns to ice on a glacier; resulting in the glacier flowing down slope. The distance the glacier expands every year is the accumulation. Ablation is just the opposite. When glaciers actually melt, and retract this is referred to as ablation.

This natural cycle of accumulation and ablation has been thrown completely out of sync in the past century due to climate change. Some of the climate change is natural, but some is also the result of human influences on the environment. In many glaciers ablation is occurring at a faster rate than accumulation; resulting in the overall decrease in ice cover.

Alchemy

Glaciers have two main types of movement. The Basal sliding that the article describes is one way that glaciers move; although, this type of movement is more common at the toe of a glacier. This type of movement leaves behind characteristic grooves and valleys running parallel to the glaciers flow (Cirque glaciers actually leave behind bowls). Glaciers also leave their mark on the terminal landscape of the glacier. These can range from alluvial and till deposits to moraines, eskers, and kettles.

The other type of glacial movement is internal flow. The article did not touch on this type of glacial movement, but it is very significant. At the head of the glacier, friction holds the glacier to the bedrock, but internal stress causes the glacier to creep along its internal planes. This causes the glacier to move from its interior, with the oldest ice remaining at the depths of the glaciers highest elevation.

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    • Pressure and temperature variations help determine how glaciers move.
      By: elnavegante
      Pressure and temperature variations help determine how glaciers move.