Weathering

If one could speed up the Earth, in time, one would see mountains forming, then breaking down to bedrock, minerals dissolving in water, and reassembling by chemical processes to mineral then rocks.  Landforms would be undergoing a continual movement of growth and denudation.  This denudation is a process of wearing away or rearranging landforms.  A constant upward, downwards, and sideways motion would be observed - the planet moving to the  song of weathering, mass movement, erosion, transportation, and deposition, sung by moving water, air, waves, ice - the strings plucked by gravity.  All notes rushing toward equilibrium --> imbalance --> equilibrium .  The geomorphic threshold "is the point at which there is enough energy to overcome resistance to movement" - a seesaw between exogenic/endogenic events and the trend toward equilibrium.  The constant weathering of the upper surface of bedrock creates broken-up rock, is called regolith. 

Some of my Notes from class:

Definition of weathering:  The breaking down of rocks into mineral particles by mechanical means, or by dissolving in water.

Physical Weathering

• Making little rocks from big rocks – a mechanical process
• Process exposes more rock mass for additional weathering – both physical and chemical

Types of physical weathering:

• Frost Action
• Crystallization
• Pressure-Release Jointing
• Biological

Biological Weathering

1. Roots – growth in crack and fissures → break up of rock
2. Bioturbation – mixing of soil by worms (earthworms) and burrowing animals (gophers)
3. Chelation – alternative wet and dry lichen activity (algae and fungi) on exposed bedrock (Canadian Shield) → disintegration of the rock
4. Humans

Chemical Weathering

Chemical weathering – decomposition of minerals in rock – involves reactions between air and water and minerals in rocks.

• Minerals combine with oxygen or carbon dioxide from atmosphere → dissolve and combine with water
• Water is abundant – has incredible ability to dissolve matter

Chemical Rock Weathering

Rocks can be chemically altered, for example:

Granite

Quartz minerals in granite more resistant to chemical weathering than feldspar → clay

Limestone

Rock enters into solution → washes away

Types of chemical weathering:

• Hydration and Hydrolysis
• Oxidation
• Carbonation and Solution
• Biological

 Formation of Karst  

• Limestone / dolomite bedrock formations develop into karst topography if the following conditions are met:
• At least 80% of formation composed of calcium carbonate materials
• Formations are jointed
• Formations are aerated
• Vegetation available to provide organic acids - enhances solution processes
• Features include: Subsurface channels, sinkholes, caverns, and steep slopes

 Sources: Wikapedia
Canadian Geosystems, Christopherson/Byrne