EXOGENETIC FORCES.pptx

GEOMORPHOLOGY

1. The ENDOGENIC forces are mainly land building forces. Diastrophism Volcanism The EXOGENIC processes are mainly land wearing forces. Weathering Mass wasting/Movement Erosion Deposition

2. Types of Movements

3. The ENDOGENIC forces are mainly land building forces. Diastrophism Volcanism The EXOGENIC processes are mainly land wearing forces. Weathering Mass wasting/Movement Erosion Deposition

4. EXOGENIC FORCES These forces derive their energy from atmosphere. Force applied per unit area is called Stress. Temperature, precipitation and structure of rocks are important elements that control various exogenic processes All the exogenic processes are covered under a general term DENUDATION. The word DENUDE means UNCOVER. Weathering, Mass wasting/Movement, Erosion and Transportation are included in denudation

5. Exogenic Processes or Denudation The processes which occur on the earth’s surface due to the influence of exogenic forces are called exogenic processes or exogenic geomorphic processes. Weathering, mass wasting, erosion, and deposition  are the main exogenic processes. All the exogenic processes are covered under a general term-  denudation , which means strip off or uncovers. The elements of nature capable of doing these exogenic processes are termed geomorphic agents (or exogenic geomorphic agents). E.g. the wind, water, waves etc.

6. DENUDATIONAL PROCESSES WEATHERING MASS MOVEMENT EROSION/ TRANSPORTATION GRAVITATIONAL/ STRESS OR CHEMICAL ACTIONS GRAVITATIONAL FORCES KINETIC ENERGY ENERGY PROCESS The effects of most of the exogenic processes are small and slow

7. WEATHERING Mechanical disintegration and chemical decomposition of rocks. Weathering processes are conditioned by many complex geological, climatic, topographic and vegetative factors. Weathering processes vary from climate and depth. When rocks undergo weathering, some minerals are removed through chemical/ physical leaching by groundwater and thereby the concentration of remaining (valuable) minerals increase.

8. Very rarely does any one of these processes ever operate completely by itself but dominance of one processes can be seen.

9. Physical weathering Physical or mechanical weathering processes depend on Gravitational forces Expansion forces due to temperature changes or animal activity Water pressure controlled by wetting and drying cycles

10. FREEZING, THAWING AND FROST WEDGING Cycles of freezing and thawing (the weather becomes warmer and causes snow and ice to melt) cause frost weathering. It is most effective at high elevations in mid-latitude where freezing and melting is often repeated. Rapid freezing of water causes its sudden expansion and high pressure. The resulting expansion affects joints, cracks, and small intergranular fractures to become wider and wider till the rock breaks apart.

11. Exfoliation-Onion / Spheroidal Removal of overlying rock load because of continued erosion causes vertical pressure release. Thus, the upper layers of the remaining rock expand to produce disintegration of rock masses. Fractures will develop roughly parallel to the ground surface. In areas of curved ground surfaces, arched fractures tend to produce massive sheets or  exfoliated slabs. Exfoliation is a result but not a process. Flaking off of more or less curved sheets of shells from over rocks or bedrocks results in smooth and rounded surfaces. So, unloading and expansion create largely, smooth rounded domes called  exfoliation domes.

12. BIOLOGICAL WEATHERING Human Activity Small organisms and dead animals Leaves and roots of trees

13. MASS Movement These movements transfer the mass of rock debris down the slope under the  direct influence of gravity . Mass movements are very active over weathered slopes rather than over unweathered slopes. Usual geographic agents like running water, glaciers, wind, waves etc do not have much role to play in mass movements, and it is gravity, which is the main driving force.

14. SLOW MASS MOVEMENTS CREEP : It occurs on moderately steep, soil-covered slopes (doesn’t need to be lubricated with water as in solifluction ). The movement is extremely slow and imperceptible except through extended observation. SOLIFLUCTION : It is the process of slow downslope flowing of soil mass or fine-grained rock debris saturated or  lubricated with water . It can be said as a type of creep with lubricated water influences the movement. It mainly occurs in permafrost regions as the layers of groundwater are occupied in between permanently frozen soil and rocks

15. Sudden/Rapid Movements A) EARTHFLOW: The movement of water-saturated clayey or silty earth materials down low angle terraces or hillsides is called earthflow . B) MUDFLOW: In the absence of vegetation and cover and with heavy rainfall, thick layers of weathered materials get saturated with water and either slow or rapidly flow down along definite channels is called as a mudflow. C) DEBRIS AVALANCHE: It is more in humid regions with or without vegetation. It occurs in narrow tracks on steep slopes and is similar to snow avalanche.

16. GEOMORPHIC AGENTS Any exogenic element of nature capable of acquiring and transporting earth materials. Running water Moving ice mass Wind Waves and currents

17. EROSIONAL LANDFORMS

18. DEPOSITIONAL LANDFORMS DELTA

19. Landforms associated with Ground water

20. Erosional Landforms- Ground water Caves

21. Depositional Landforms- Ground Water

22. Erosional Landforms –WIND/AEOLIAN

23. Depositional Landforms- WIND