Diastrophism refers to all processes that move, elevate, or deform the earth's crust due to diastrophic (deforming) movements. These are also called deforming movements or slow movements. As part of the geography curriculum, students are expected to learn about slow movement and diastrophism. Diastrophism, or slow movement, is a key concept in the UPSC exam.

Slow Movements or Diastrophism

• Diastrophism refers to all processes that move, elevate, or deformation of the earth's crust due to diastrophic movements (deforming movements) such as folding, faulting, warping (bending or twisting of a large area), and fracturing.
• Diastrophism encompasses all processes that move, elevate, or build-up sections of the earth's crust.
• Diastrophic changes are slow and can last for thousands of years.

History Behind Slow Movements (Diastrophism)

• By the end of the nineteenth century, it was widely believed that the reason for folding and faults was lateral compression produced by the Earth's gradual cooling, which resulted in a decreasing Earth.
• Eduard Suess proposed his eustatic hypothesis which formed the foundation for Chamberlin's explanation of diastrophism.
• Suess stated his conviction that the rise and fall of sea levels could be mapped over the globe over geologic time.
• Suess proposed that sea levels steadily rose as sediments filled ocean basins and that periodic events of fast ocean-bottom subsidence increased the ocean's capacity and produced the regressions.
• Diastrophic movement, according to Chamberlin, is generated by gravitational contraction rather than thermal contraction.
• Thermal convection did not supplant the shrinking Earth hypothesis in the United States until the late 1960s.

Classification of Diastrophic or Slow Movements

Diastrophic movements are further classified into epeirogenic movements and orogenic movements.

Orogenic Process

• Orogenic movements/ processes, which include mountain-building through extreme folding and influence long and narrow regions of the earth's crust, are among them.
• Orogenic or mountain-forming movements act tangentially to the earth's surface, as in plate tectonics. The Himalayan-Alpine orogeny is the best instance of this case.
• These processes are further classified into Tension and Compression.
• Fissures are caused by tension i.e., when force is acting away from a point in two directions.
  • The Sierra Nevada (The USA) mountain range is the best example of a mountain that is formed by tension.
• Folds appear as a result of compression i.e., when force is acting towards a point.
  • The Himalayas is the best example of a mountain that is formed by compression.

Epeirogenic Process

• Movements that form continents are known as epeirogenic or continent-forming movements. They are also known as radial movements because they act along the radius of the earth.
• They can move towards (subsidence) or away from (uplift) the center.
• They create land upheavals or depressions with long-wavelength undulations (wavy surface) and little folding.
• The present-day drainage divides between Limpopo and Zambezi rivers in southern Africa is a classic example of this type.
• Subsidence occurs when movement is in a downward direction.
• It is uplifted from the center when it is away. Raised beaches, elevated wave-cut terraces, sea caves, and so on are examples of uplift

Epeirogenic movements are further classified into Downward and Upward.

Downward Epeirogenic Movements

• Subsidence occurs when movement is in a downward direction.
• Subsidence is evidenced by submerged forests and valleys, as well as structures.
• A section of the Rann of Kachchh was inundated due to an earthquake in 1819.
• Subsidence is evidenced by the presence of peat and lignite beds below sea level in Thirunelveli (Tamil Nadu) and the Sunderbans(West Bengal).
• The submergence of the intervening terrain has cut the Andamans and Nicobars off from the Arakan coast.
• Trees have been discovered embedded in the mud about 4 meters below the low tide line on the east side of Bombay Island. On the Thirunelveli coast in Tamil Nadu, a similar submerged forest has been discovered.
• A substantial portion of the Gulf of Mannar and Palk Strait is quite shallow and was recently submerged.
• The sea has flooded a portion of the former town of Mahabalipuram near Chennai (Madras).

Upward Epeirogenic Movements

• It is uplifted from the center when it is away. Raised beaches, elevated wave-cut terraces, sea caves, and so on are examples of uplift.
• Uplift is evidenced by elevated beaches, elevated wave-cut terraces, sea caves, and fossiliferous deposits above sea level.
• Raised beaches can be seen around the Kathiawar, Nellore, and Thirunelveli coasts, with some rising as high as 15 to 30 meters above the current sea level.
• Several locations that were once on the sea have relocated a few miles inland.
• Coringa near the Godavari's mouth, Kaveripattinam in the Kaveri delta, and Korkai on the coast of Thirunelveli, for example, were all thriving seaports 1,000 to 2,000 years ago.

Significance of Diastrophism

Formation of Landforms

• Diastrophism is responsible for creating a range of landforms, from mountain ranges to plateaus and basins.
• For instance, the Himalayas, Alps, and Andes have formed as a result of orogenic movements.
• Epeirogenic movements can raise or lower continental blocks, leading to the formation of continental shelves or interior basins.

Influence on Climate

• The formation of mountain ranges can act as barriers to moisture-laden winds, leading to orographic rainfall on the windward side and creating rain shadows on the leeward side.
• Mountain ranges can also influence atmospheric circulation patterns and jet streams.

Biodiversity Hotspots

• Mountain ranges and highlands, often products of diastrophism, can act as isolated ecosystems leading to speciation and high biodiversity.
• For example, the Western Ghats in India, a product of tectonic forces, is one of the world's biodiversity hotspots.

Influence on Human Settlements

• Regions uplifted due to diastrophism can influence river courses, leading to fertile plains suitable for agriculture and human settlement.
• Conversely, certain areas might become uninhabitable due to extreme elevation or rugged terrain.

Impacts on Ocean Circulation

• The rise or fall of land can influence ocean currents. For instance, the uplift of the Isthmus of Panama separated the Pacific and Atlantic Oceans, altering oceanic circulation and having global climatic implications.

Scientific Understanding

• Studying diastrophism offers insights into the Earth's internal processes, plate tectonics, and the dynamic nature of the planet's crust.
• It aids in understanding the Earth's geological history and predicting future movements or changes.

Conclusion

Diastrophism plays a crucial role in shaping the Earth's topography. The forces responsible for diastrophic movements are built up over long periods, and while they act slowly, they have immense power and can produce significant deformations in the Earth's crust.

FAQs

MCQs

1. Which type of diastrophic movement is responsible for the gradual uplift of continents?

A) Folding
B) Faulting
C) Epeirogeny
D) Vulcanism

2. Diastrophic movements that do NOT cause significant folding or faulting are known as:

A) Epeirogenic movements
B) Orogenic movements
C) Sudden movements
D) Vulcanism

3. Which landform is commonly associated with epeirogenic movements?

A) Fold mountains
B) Plateaus
C) Volcanic cones
D) Rift valleys

4. The term "diastrophism" is most closely related to:

A) River erosion
B) Tectonic deformation
C) Weathering
D) Ocean currents

5. Which is NOT an example of diastrophic movement?

A) Faulting
B) Folding
C) Sediment deposition
D) Epeirogeny

GS Mains Questions and Model Answers

Q1: Explain the role of slow diastrophic movements in shaping the Earth’s surface. How do they differ from sudden tectonic movements?

Answer: Slow diastrophic movements, like epeirogeny, gradually uplift or depress large crustal areas without causing intense folding or faulting. This results in broad structural changes, forming plateaus or basins over millions of years. Unlike sudden tectonic movements (e.g., earthquakes) that occur rapidly and lead to abrupt changes, slow movements create stable landforms over extended periods, significantly influencing topography and geology. They contribute to landscape evolution by maintaining structural stability, fostering ecosystems, and affecting human settlement patterns.

Q2: Discuss the impact of epeirogenic movements on continental landforms. Provide examples of specific landforms resulting from these movements.

Answer: Epeirogenic movements, characterized by gradual vertical shifts, uplift continents, forming plateaus (e.g., Deccan Plateau) or depress basins. Unlike orogenic (mountain-building) processes, epeirogenic movements affect vast areas without intense folding. Such movements enhance biodiversity and allow for soil stabilization. Plateaus like the Colorado Plateau exhibit rich geological records, while subsidence in regions like the Ganges Basin supports fertile floodplains, both examples illustrating the geological and ecological impacts of epeirogenic movements.

Q3: How does diastrophism influence climate and ecosystems? Analyze with examples from India.

Answer: Diastrophism, by shaping landforms, indirectly affects regional climates and ecosystems. Elevated regions like the Himalayas impact monsoon patterns, directing rainfall and influencing biodiversity. In India, the Western Ghats, formed through tectonic uplift, support unique ecosystems due to their elevation and climatic conditions. Plateaus, such as the Chota Nagpur, affect soil types and vegetation patterns, supporting distinct ecosystems. Thus, diastrophic activity plays a crucial role in regional ecological and climatic dynamics.

Previous Year Questions on Diastrophism

1. UPSC CSE Prelims 2021:

Question: Epeirogenic movements are primarily associated with which of the following landforms?

A) Rift valleys
B) Plateaus
C) Fold mountains
D) Volcanoes

Answer: (B)

Explanation: Plateaus are often formed due to epeirogenic movements, which are slow uplifts or subsidence affecting large crustal areas without intense folding or faulting.

2. UPSC CSE Mains 2020 (GS Paper 1):

Question: "Analyze the influence of slow diastrophic movements on landform development in India. How do these movements impact agriculture and settlement patterns?"

Answer: Slow diastrophic movements, like epeirogeny, shape Indian plateaus and basins, influencing topography, soil fertility, and water retention, which are crucial for agriculture. For example, the Deccan Plateau’s stability supports dense settlements and extensive agriculture. Uplifts in the Western Ghats influence rainfall distribution, further impacting agriculture and human settlement.