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:
Biological Weathering
Roots – growth in crack and fissures → break up of rock
Bioturbation – mixing of soil by worms (earthworms) and burrowing animals (gophers)
Chelation – alternative wet and dry lichen activity (algae and fungi) on exposed bedrock (Canadian Shield) → disintegration of the rock
Humans
Chemical Weathering
Chemical weathering – decomposition of minerals in rock – involves reactions between air and water and minerals in rocks.
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