Weathering in Glacial Landscapes

• A ubiquitous process (meaning that it happens everywhere)
• In glacial landscapes, some types of weathering are significant
• Uses heat energy

• Produces smaller fragments of the same rock
• No chemical alterations
• Some processes are ineffective above 0°c

Freeze-thaw

• Water enters cracks/joints
• Expands by nearly 10% when freezes
• This exurts pressure causing the rock to split
• The more frequent the temperature is around 0, the more effective this process is

Frost Shattering

• At extremely low temperatures
• Water is trapped in rock pores
• Freezes and expands to create stress
• Distintigrates the rock

Pressure Release

• When weight of overlaying ice is lost due to melting
• Underlaying rock expands expands and fractures
• Parallel to the surface
• Exposing the sub-surface rocks

Exfoliation

• Peeling away of sheets of rock millimeteres to metres from rock's surface
• Due to a range of physical and chemical factors

Controlling Factors

• On higher land there is a better chance for active water movement
• Grand slope controls the mechanical disintegration of rock

• Involves chemical reaction between elements of weather and mierals within the rock
• Van't-Hoff's Law- 10°c increase causes 2.5 times increase in the rate of chemical reaction

Oxidation

• Some minerals react with oxygen (especially iron)
• Becomes soluble under extremely acidic conditions
• Original structure is destroyed

Carbonation

• Rainwater combines with dissolved co2 from atmosphere to produce a weal carbonic acid
• This reacts with calcium carbonate to produce calcium bicarnbonate -> soluble
• Is reversable and precipitation of calcite happens during evaporation of calcium rich water

Solution

• Some salts are soluble in water
• Others are only in very acidic water (pH about 3)
• Solution is any process where a mineral dissolves in water
• Mineral specific processed can be identified

Hydrolysis

• Chemical reaction between rock minerals and water
• Silicates combine with water to make secondary minerals such as clay

Hydration

• Water molecules are added to rock minerals creating new minerals of a larger volume
• As some absorb water some minerals expand

Controlling Factors

• Rock jointing (makes larger surface available), Chemical composition, Pore spaces of bedrock and regolith, Mohs scale of hardness

• Usually classed as a weathering type despite not fitting the precise definition of weathering
• Little significance in glaciers due to a lack to plant and animal life

Physical Action

• Burrowing animals
• Tree roots grow into joints/cracks exerting outward pressure
• Similar effects to freeze-that
• When trees topple, roots exert leverage

Chemical Action

• Chelation
• Organic acids produced during decomposition of animal/plant litter cause soil water to become more acidic
• Reacts with some minerals

Controlling Factors

• Largely controlled by the presence or absence of vegetation in a particular region
• The microorganisms associated with the roots of plants and trees encourage decomposition and disintegration of rocks through physio-biochemical weathering.
• Due to the important roles of temperature and water and their consequent effect on organisms, it has been suggested that they can be related to climatic zones