Question

Describe two ways that glacier ice can move across the surface.

Short answer

Glaciers move via internal deformation and basal sliding.

Step-by-step solution

Understanding Glacier Movement

Glaciers primarily move through two processes: internal deformation and basal sliding. Understanding these mechanisms is key to explaining how glacier ice can travel across the earth's surface.

Internal Deformation Explanation

Internal deformation occurs when the ice within the glacier deforms under the pressure of its own weight. The immense weight of the accumulated ice causes the individual ice crystals to change shape and allow the glacier to flow internally. This is a slow process and depends on the temperature and pressure conditions within the glacier.

Basal Sliding Explanation

Basal sliding happens when the entire glacier slides over the bedrock beneath it. This movement is facilitated by a thin layer of water or sediment between the glacier base and the bedrock. The water reduces friction, allowing the glacier to slide more easily. This type of movement can be influenced by climatic factors such as temperature, which may increase melting and provide more water for sliding.

Key concepts

Internal Deformation

In glaciers, internal deformation is one of the key processes that facilitate movement. This process involves the deformation of ice crystals within the glacier under the enormous pressure exerted by the glacier's mass. When a glacier becomes sufficiently heavy, the pressure causes the ice within to behave plastically, allowing it to flow slowly. This flow occurs as the individual ice crystals bend and realign over time.
\[ \text{Rate of deformation} = \text{factors such as } \frac{\text{temperature}}{\text{stress}} \]
These factors include the temperature within the glacier and the stress or pressure it experiences. High pressure combined with the ice's inherent properties makes internal deformation an ongoing, gradual process.

• The deformation rate can increase with warmer temperatures, as warmer ice is more pliable.
• Pressure differences within the glacier can create zones of faster or slower movement.

This process is essential for understanding the slow yet powerful movement of glaciers down valleys.

Basal Sliding

Basal sliding allows a glacier to move more rapidly over the bedrock by the presence of a thin layer of water or wet sediment at its base. This water acts as a lubricant, significantly reducing friction between the glacier and the bedrock. This form of glacier movement is particularly sensitive to environmental conditions. For example, warmer temperatures can enhance the melting of ice, increasing the water available for basal sliding.
Several factors are key in this process:

• The presence of geothermal heat, which can melt ice at the glacier's base.
• Seasonal meltwater from the glacier surface that percolates down to its base.
• Pressure melting, where the immense weight of the glacier causes ice to melt under pressure.

Basal sliding can lead to rapid glacier movement, particularly during warmer months or in regions with significant geothermal activity.

Glacier Ice Dynamics

Glacier ice dynamics encompass the various mechanisms and interactions that govern how glaciers move and change over time. This includes both internal deformation and basal sliding as well as their complex interactions. The study of glacier ice dynamics examines how factors such as gravity, thermal conditions, and hydrological processes impact glacier motion.
Key influences on glacier ice dynamics include:

• Climatic conditions which affect ice temperature and melting rates.
• The geographical slope, which influences how gravity drives glacier flow.
• The presence of debris within the ice, which can affect movement speed.

Understanding these dynamics is crucial for predicting glacier behavior, especially in a warming climate. This helps scientists anticipate how glaciers might contribute to sea-level rise and the changing landscape.