Folds in landforms and their Causes (Geography)

In geography, folds are wave-like bends or curves in rock layers caused by Earth's internal forces, typically compression. These bends can form upward (anticlines) or downward (synclines) structures, contributing to the formation of mountain ranges and other landforms. 
folds in landforms, particularly fold mountains, predominantly occur near the margins of tectonic plates.
Plate Convergence: Fold mountains form when two tectonic plates collide. The immense pressure from this collision forces the Earth's crust to buckle and fold, creating the characteristic mountain ranges.  
Types of Plate Boundaries:
Convergent Continental-Continental Boundaries (C=C): When two continental plates collide, neither can subduct due to their similar densities. This leads to intense compression and the formation of major fold mountain ranges like the Himalayas.  
Convergent Oceanic-Continental Boundaries(O=C): When an oceanic plate collides with a continental plate, the denser oceanic plate subducts beneath the continental plate. This can also lead to the formation of fold mountains along the continental margin, such as the Andes Mountains.  
Folds in landforms are often associated with the margins of tectonic plates because this is where significant compressional forces occur due to plate interactions. These forces cause the rock layers to bend and form folds. For example, mountain ranges like the Himalayas and the Alps are formed by the folding of the Earth's crust at convergent plate boundaries.
However, folds can also occur in other geological settings, including plateaus, plains, and low-lying regions. Here’s how:
Intraplate Folding: Folding can occur within a tectonic plate due to internal stresses, even if the region is not near a plate boundary. This can result from processes like subsurface faulting or differential loading.
Sedimentary Basins: In regions where, sedimentary layers accumulate over time, folds can develop due to the weight and pressure of overlying sediments, as well as due to subsurface movements.
Local Tectonics: Even in relatively stable regions, local tectonic forces can create folds. For example, regions with ancient orogenies (mountain-building events) may still exhibit folding.

1. Folds Presented By: Ankita Khobragade  NET, SET, Research Scholar (Geography) NFSC - SRF Vasantrao Naik Government Institute of Arts and Social Sciences Nagpur

2. Folds: In geography, folds are wave-like bends or curves in rock layers caused by Earth's internal forces, typically compression. These bends can form upward (anticlines) or downward (synclines) structures, contributing to the formation of mountain ranges and other landforms. 

3. Causes of folds:

4. Rates of Plate Movement The Arctic Ridge has the slowest rate (less than 2.5 cm/year), and the East Pacific Rise in the South Pacific (about 3,400 km west of Chile), has the fastest rate (more than 15 cm/year). Major tectonic plates Antarctica and the surrounding oceanic plate North American plate South American plate Pacific plate India-Australia-New Zealand plate Africa with the eastern Atlantic floor plate Eurasia and the adjacent oceanic plate Minor tectonic plates Cocos plate: Between Central America and Pacific plate Nazca plate: Between South America and Pacific plate Arabian plate: Mostly the Saudi Arabian landmass Philippine plate: Between the Asiatic and Pacific plate Caroline plate: Between the Philippine and Indian plate (North of New Guinea) Fuji plate: North-east of Australia Turkish plate Aegean plate (Mediterranean region) Caribbean plate Juan de Fuca plate (between Pacific and North American plates) Iranian plate.

5. folds in landforms, particularly fold mountains, predominantly occur near the margins of tectonic plates. Plate Convergence: Fold mountains form when two tectonic plates collide. The immense pressure from this collision forces the Earth's crust to buckle and fold, creating the characteristic mountain ranges.   Types of Plate Boundaries: Convergent Continental-Continental Boundaries (C=C): When two continental plates collide, neither can subduct due to their similar densities . This leads to intense compression and the formation of major fold mountain ranges like the Himalayas.   Convergent Oceanic-Continental Boundaries(O=C): When an oceanic plate collides with a continental plate, the denser oceanic plate subducts beneath the continental plate . This can also lead to the formation of fold mountains along the continental margin, such as the Andes Mountains.  

6. Folds in landforms are often associated with the margins of tectonic plates because this is where significant compressional forces occur due to plate interactions . These forces cause the rock layers to bend and form folds. For example, mountain ranges like the Himalayas and the Alps are formed by the folding of the Earth's crust at convergent plate boundaries. However, folds can also occur in other geological settings, including plateaus, plains, and low-lying regions. Here’s how: Intraplate Folding : Folding can occur within a tectonic plate due to internal stresses , even if the region is not near a plate boundary. This can result from processes like subsurface faulting or differential loading. Sedimentary Basins : In regions where, sedimentary layers accumulate over time, folds can develop due to the weight and pressure of overlying sediments, as well as due to subsurface movements. Local Tectonics : Even in relatively stable regions, local tectonic forces can create folds. For example, regions with ancient orogenies (mountain-building events) may still exhibit folding.

7. Symmetrical fold is one where two limbs dip at the same angle but in opposite directions. Asymmetrical fold is one whose limbs dip at unequal angles in opposite directions. Isoclinal fold have parallel limbs which dip at the same angle in the same directions. Overturned fold is an asymmetrical fold whose one limb is turned past the vertical . Recumbent fold is one in which both the limbs become almost horizontal . Chevron fold have straight or nearly straight limbs .

8. Type of Fold : Anticline Pictures : This anticline is in Alberta, Canada in the Rocky Mountains Description : Upward-arching fold with the oldest rocks at the core. Angle of Inclination : Steep to gentle Prerequisite Type of Rocks : Sedimentary or metamorphic rocks Real-World Example : Appalachian Mountains (USA), Alps, Andes, and Rockies. India Example : Himalayan Anticlines, Aravalli Range Maharashtra Example : Satpura Ranges, Western Ghats Anthropogenic Activities for Resource Extraction : Mining of coal, petroleum, and natural gas within anticline traps. Reason for Suitability (and Exclusion of Others) : Acts as traps for hydrocarbons due to overlying impermeable rocks. Poor suitability for groundwater due to elevated structure causing minimal recharge. Anticline folds:

9. Anticline folds: Syncline folds: Overturned Folds: Recumbent Folds:

10. Type of Fold : Syncline Description : Downward-arching fold with youngest rocks at the core. Angle of Inclination : Steep to gentle Prerequisite Type of Rocks : Sedimentary or metamorphic rocks Real-World Example : Jura Mountains (Switzerland), Paris Basin in France India Example : Himalayan Synclines, Shillong Plateau Maharashtra Example : Vidarbha Region (Coal Belts), Bhor Ghat region Anthropogenic Activities for Resource Extraction : Extraction of coal and groundwater reserves due to natural trapping. Reason for Suitability (and Exclusion of Others) : Accumulates water and sediments, ideal for aquifers and coal. Lacks upward traps for hydrocarbons. Syncline folds:

11. Type of Fold : Overturned Fold Description : One limb is tilted beyond vertical due to extreme compression. Angle of Inclination : Steep to nearly vertical Prerequisite Type of Rocks : Sedimentary and metamorphic Real-World Example : Rocky Mountains (USA) India Example : Himachal Himalayas Maharashtra Example : Sahyadri Ranges Anthropogenic Activities for Resource Extraction : Mining activités ( iron , manganese , bauxite). Reason for Suitability (and Exclusion of Others) : Exposes minerals due to compression. Poor trapping for hydrocarbons due to disrupted geometry. Overturned Folds:

12. Recumbent fold in Black Hills, South Dakota, USA Type of Fold : Recumbent Fold Description : Horizontally compressed fold with limbs nearly parallel to the ground. Angle of Inclination : Horizontal Prerequisite Type of Rocks : Highly compressed sedimentary Real-World Example : Alps (Europe) India Example : Western Himalayan Region Maharashtra Example : Western Ghats Anthropogenic Activities for Resource Extraction : Hydrocarbon extraction, tunnel construction for mining and transportation. Reason for Suitability (and Exclusion of Others) : Forms sealed reservoirs and allows tunnels. Unsuitable for groundwater due to disrupted recharge. Recumbent Folds:

13. Type of Fold : Isoclinal Fold Description : Parallel limbs and equal angles of inclination; formed under extreme compression. Angle of Inclination : Nearly parallel Prerequisite Type of Rocks : Homogeneous rock layers Real-World Example : Andes (South America) India Example : Ladakh Region Maharashtra Example : Gadchiroli Region Anthropogenic Activities for Resource Extraction : Extraction of valuable ores like copper and iron. Reason for Suitability (and Exclusion of Others) : Compression concentrates ores in fractures. Geometry unsuitable for oil/gas trapping. Isoclinal Fold s:

14. Type of Fold : Chevron Fold Pictures : Chevron folds with flat-lying axial planes, Millook Haven, North Cornwall, UK Description : Sharp, angular folds with straight limbs and narrow hinges. Angle of Inclination : Sharp, angular inclination Prerequisite Type of Rocks : Thinly bedded sedimentary layers Real-World Example : Appalachian Basin (USA) India Example : Himalayas, Narmada Belt Maharashtra Example : Satpura Ranges Anthropogenic Activities for Resource Extraction : Quarrying of angular strata for construction materials. Reason for Suitability (and Exclusion of Others) : Exposes straight limbs, simplifying access. Disrupts continuity for hydrocarbons and aquifers. Chevron Folds:

15. Type of Fold : Monocline Fold Description : Step-like fold where rock layers have one steep limb with the other relatively horizontal. Angle of Inclination : One limb steep Prerequisite Type of Rocks : Sedimentary Real-World Example : Monument Valley (USA) India Example : Great Vindhyan Escarpment Maharashtra Example : Deccan Traps (Limited Expression) Anthropogenic Activities for Resource Extraction : Suitable for accessing strata with oil/gas or coal reserves. Reason for Suitability (and Exclusion of Others) : Easy drilling along monoclines for oil and coal but minimal groundwater due to incomplete trapping. Monocline Folds:

16. Type of Fold : Nappes Description : Large-scale overturned folds thrust over one another, forming stacked structures. Angle of Inclination : Low to high inclination depending on thrusting. Prerequisite Type of Rocks : Sedimentary and metamorphic Real-World Example : Swiss Alps India Example : Garhwal Himalayas Maharashtra Example : Sahyadri Highlands Anthropogenic Activities for Resource Extraction : Gold, copper, and valuable ore mining. Reason for Suitability (and Exclusion of Others) : Intense deformation enriches ore deposits. Poor groundwater or hydrocarbon trapping due to chaotic structure. Nappes:

17. Type of Fold : Symmetrical Fold Description : Limbs are mirror images of each other; fold axis is vertical. Angle of Inclination : Symmetrical Prerequisite Type of Rocks : Uniformly bedded sedimentary Real-World Example : Appalachian Synclines (USA) India Example : Naga Hills Maharashtra Example : Chandrapur Coalfields Anthropogenic Activities for Resource Extraction : Suitable for coal and ore mining. Reason for Suitability (and Exclusion of Others) : Consistency of layering enhances ore deposits and hydrocarbon traps. Poor suitability for water storage in rigid layers. Symmetrical Folds: Anticline Syncline

18. Type of Fold : Asymmetrical Fold, Overturned folds, Recumbent folds Description : One limb is steeper than the other due to uneven compression. Angle of Inclination : Uneven inclination Prerequisite Type of Rocks : Sedimentary and metamorphic Real-World Example : Himalayas India Example : Western Ghats Maharashtra Example : Sahyadri Escarpment Anthropogenic Activities for Resource Extraction : Facilitates ore deposits and mining activities. Reason for Suitability (and Exclusion of Others) : Compression exposes valuable mineral veins. Lack of continuity reduces efficiency for hydrocarbons. Asymmetrical Folds:

19. Type of Fold : Plunge Fold Description : Fold axis is tilted, forming a plunging geometry. A plunging fold is a type of fold where the fold hinge line is not horizontal but dips or plunges into the Earth Angle of Inclination : Moderate to steep plunge Prerequisite Type of Rocks : Sedimentary, volcanic Real-World Example : Rockies (USA), Alps (Europe) India Example : Aravalli Hills Maharashtra Example : Satmala Range Anthropogenic Activities for Resource Extraction : Mining for metals like gold and copper. Reason for Suitability (and Exclusion of Others) : Tilted strata facilitate the exposure of metal ores but disrupt fluid reservoirs for hydrocarbons or water. Plunge Folds:

20. Plunge Folds:

21. Plunge Folds:

22. Type of Fold : Fan Fold Description : Limbs diverge away from each other, forming a fan-shaped structure. Angle of Inclination : Wide to steep divergence Prerequisite Type of Rocks : Soft sedimentary layers Real-World Example : Andes (South America) India Example : Kumaon Himalayas Maharashtra Example : Sahyadri Foothills Anthropogenic Activities for Resource Extraction : Extracting sediments, aggregates, and groundwater. Reason for Suitability (and Exclusion of Others) : Diverging structure accumulates sediments, providing access to aggregates and aquifers. Fan Folds:

23. Type of Fold : Open Fold Description : Gentle fold with a large angle between limbs, created under light compression. Angle of Inclination : Gentle inclination Prerequisite Type of Rocks : Sedimentary Real-World Example : Zagros Mountains (Iran) India Example : Vindhyan Hills Maharashtra Example : Wardha Coal Belts Anthropogenic Activities for Resource Extraction : Facilitates coal and hydrocarbon extraction. Reason for Suitability (and Exclusion of Others) : Less deformation maintains intact reservoirs for hydrocarbons and groundwater. Open Folds:

24. Type of Fold : Closed Fold Description : Tight fold with a small angle between limbs due to intense compression. Angle of Inclination : Tight inclination Prerequisite Type of Rocks : Compact sedimentary, metamorphic Real-World Example : Alps (Europe), Andes India Example : Ladakh Maharashtra Example : Satpura Hills Anthropogenic Activities for Resource Extraction : Ore extraction (iron, copper). Reason for Suitability (and Exclusion of Others) : Intense folding leads to enriched mineral veins but disrupts continuous reservoirs for fluids. Closed Folds:

25. Type of Fold : Dome (anticlines) Description : Broad, upward bulge resembling an anticline but circular in pattern. Angle of Inclination : Radial inclination outward Prerequisite Type of Rocks : Sedimentary overlying igneous Real-World Example : Black Hills, South Dakota (USA) India Example : Vindhyan Dome Region Maharashtra Example : Deccan Plateau Anthropogenic Activities for Resource Extraction : Oil, natural gas, and mineral resource extraction within dome traps. Reason for Suitability (and Exclusion of Others) : Traps hydrocarbons and minerals at the core. Outward dips reduce groundwater storage. Dome:

26. Type of Fold : Basin (synclines) Description : Downward, bowl-shaped fold with rocks dipping towards the center. Angle of Inclination : Radial inclination inward Prerequisite Type of Rocks : Sedimentary Real-World Example : Michigan Basin (USA) India Example : Cambay Basin Maharashtra Example : Godavari Basin Anthropogenic Activities for Resource Extraction : Extraction of coalbed methane, oil, and groundwater reservoirs. Reason for Suitability (and Exclusion of Others) : Traps hydrocarbons, coal, and water at the center. Limited surface mineral deposits. Basin