Explain weathering and mass wasting. and describe their significance. (15 marks)
- Introduce with exogenic forces and how weather and mass wasting are types of them
- Explain weathering and briefly various types like chemical, physical and biological
- Explain mass wasting
- Describe their significance like soil formation, formation of natural resources etc.
- Conclude appropriately
Along with endogenetic forces, Earth’s surface is being continuously subjected to by external forces originating within the earth’s atmosphere (exogenic forces) like weathering, mass wasting, erosion and deposition.
Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth’s atmosphere, water, and biological organisms. Weathering occurs in situ, with little or no movement.
There are three major groups of weathering processes:
- Chemical Weathering Processes- A group of weathering processes i.e. solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface /soil water and other acids.
- Physical Weathering Processes- They are mostly due to thermal expansion, and pressure release. The repeated action of these processes cause damage to the rocks
- Biological weathering- It is contribution to or removal of minerals and ions from the weathering environment and physical changes due to growth or movement of organisms. Burrowing and wedging by organisms like earthworms, termites, rodents etc., help in exposing the new surfaces to chemical attack and assists in the penetration of moisture and air
These movements transfer the mass of rock debris down the slopes under the direct influence of gravity. While weathering is not a pre-requisite for mass movement, it aids mass movements.
- Conditions in favour: Mass movements are aided by gravity and no geomorphic agent like running water, glaciers, wind, waves and currents participate in the process of mass movements. Weak unconsolidated materials, thinly bedded rocks, faults, steeply dipping beds, vertical cliffs or steep slopes, abundant precipitation and torrential rains and scarcity of vegetation etc., favour mass movements.
- Types: The movements of mass may range from slow to rapid, affecting shallow to deep columns of materials and include creep, flow, slide and fall.
Significance of weathering and mass wasting
- Soil and Regolith: Weathering is crucial base to our ecology as it converts bed rock into regolith and soil. Regolith is also notable for being the basic source for the inorganic part of the soil.
- Resources: Weathering produces natural resources like clay, sand, gravel etc. Practically all bauxite, most iron ore and some copper ore are formed and concentrated by weathering.
- Landforms: Differential weathering helps in the evolution of different types of landforms like stone lattice, tors, buttes etc. Continuous removal and transfer of weathered materials through different processes of mass-translocation of rock wastes such as landslides and by the agent of erosion causes gradual lowering of the height of the affected area.
- Disasters: In mountainous regions, mass wasting of weathered material on the slopes occurs in the form of landslides and debris avalanches leading to loss of life and property.
The effects of most of the exogenic geomorphic processes are small and slow and may be imperceptible in a short time span, but in the long run play an important role.
Subjects : Geography – Physical