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Plate Tectonic Theory UPSC and APSC Nakshatra IAS

Plate Tectonics

Plate Tectonic Theory Nakshatra IAS
Plate Tectonic Theory Nakshatra IAS

  • The formulation of the theory of Plate Tectonics was derived from the integration of the continental drift theory, convection current theory, and the theory of seafloor spreading.

  • The hypothesis of plate tectonics was proposed by McKenzie and Parker in 1967. The theory was subsequently described by Morgan in 1968.

  • The theory of plate tectonics posits that the lithosphere of the Earth is fragmented into discrete plates that are suspended over a malleable stratum known as the asthenosphere, situated in the upper portion of the mantle.

  • The movement of plates occurs in a horizontal manner throughout the asthenosphere, with the plates behaving as rigid entities.

  • The lithosphere encompasses both the Earth's crust and the uppermost portion of the mantle. Its thickness exhibits variability, ranging from 5 to 100 km in oceanic regions and approximately 200 km in continental regions.

  • Oceanic plates primarily consist of the Simatic crust, which is comparatively thinner, whereas continental plates are composed of Sialic material and have considerably greater thickness.

  • Lithospheric plates, also known as tectonic plates, exhibit a range of sizes, encompassing both small and large plates. These plates can be classified into distinct types, including continental plates such as the Arabian plate, oceanic plates such as the Pacific plate, and occasionally a hybrid composition of both continental and oceanic plates, as exemplified by the Indo-Australian plate.

  • The displacement of these lithospheric plates (attributable to convective currents within the asthenosphere) gives rise to diverse topographical features and constitutes the primary catalyst for all geological phenomena.

The driving mechanism behind plate movement

Convection currents within the Earth's mantle are formed as a result of heat gradients.

Major and Minor Tectonic Plates
Major and Minor Tectonic Plates

Principal tectonic plates

  1. Antarctica and the surrounding oceanic plate

  2. North American plate

  3. South American plate

  4. Pacific plate

  5. India-Australia-New Zealand plate

  6. Africa with the eastern Atlantic floor plate

  7. Eurasia and the adjacent oceanic plate

Minor tectonic plates

  1. The Cocos Plate is situated in the region between Central America and the Pacific Plate.

  2. The Nazca Plate is situated in the region between the South American Plate and the Pacific Plate.

  3. The Arabian plate mostly consists of the continent of Saudi Arabia.

  4. The Philippine plate is situated in the region between the Asiatic and Pacific plates.

  5. The Caroline Plate is located in the region between the Philippine Plate and the Indian Plate, specifically to the north of New Guinea.

  6. The Fuji Plate is located in the northeastern region of Australia.

  7. The topic of discussion pertains to Turkish license plates.

  8. The Aegean plate, located in the Mediterranean region.

  9. The Caribbean plate is a tectonic plate located in the western Atlantic Ocean. It is primarily composed of oceanic crust and is

  10. The Juan de Fuca plate is situated in the region between the Pacific plate and the North American plate.

  11. The Iranian plate refers to the tectonic plate that encompasses a significant portion of Iran and its surrounding regions.

In addition to the aforementioned plates, there are numerous additional minor plates.

The formation of the majority of these small plates can be attributed to the tension induced by the convergence of large plates.

The Mediterranean Sea is partitioned into multiple smaller plates as a result of the compressive force imposed by the Eurasian and African plates.

The diagram presented below illustrates the temporal alterations in landform resulting from the interplay between several tectonic plates.

Tectonic Plates UPSC. Source; NCERT
Tectonic Plates UPSC. Source; NCERT

Body of evidence that supports the theory of plate tectonics:

1. Paleomagnetism is a scientific discipline that investigates the Earth's ancient magnetic field.

  • The rocks exhibiting paleomagnetic properties constitute a crucial body of evidence.

  • The alignment of iron grains in ancient rock formations indicates a paleomagnetic signature that suggests the presence of a historical South Pole location, situated at some point between contemporary Africa and Antarctica.

  • This phenomenon is commonly referred to as polar wandering.

2. Continental landmasses predominantly consist of older rock formations, whereas the oceanic floor is primarily composed of comparatively younger rocks.

  • Continents harbor rocks with an age reaching as far back as 3.5 billion years, yet the oldest rock discovered on the ocean floor, specifically in the western region of the Pacific Ocean, does not exceed 75 million years in age.

  • As we traverse towards elevated landforms, such as ridges, progressively more recent geological formations become evident.

  • This phenomenon indicates the successful propagation of seafloor spreading, which closely resembles plate tectonics but specifically focuses on the interaction between oceanic plates.

  • These interactions primarily occur along oceanic ridges, which serve as the boundaries between these plates.

3. Gravitational anomalies refer to deviations from the expected gravitational field strength or behavior in a given region.

  • In regions characterized by trenches resulting from subduction along convergent plate boundaries, the gravitational constant 'g' has a lower value. This observation suggests a depletion of resources.

  • As an illustration, gravity measurements conducted in the vicinity of the Indonesian islands have revealed a correlation between substantial gravity anomalies and the oceanic trench that borders Indonesia.

4. Seismic activity, specifically earthquakes and volcanoes.

  • The observation that regions along plate boundaries consistently experience seismic and volcanic activities provides empirical support for the plate tectonics theory.

The importance of Plate Tectonics

  1. The vast majority of significant landforms are a direct result of the geological process known as plate tectonics.

  2. Magmatic eruptions expel newly formed materials originating from the Earth's core.

  3. Minerals with significant economic value, such as copper and uranium, tend to be located in close proximity to plate borders.

  4. Based on current understanding of crustal plate dynamics, it is possible to make predictions regarding the future configuration of landmasses.

  5. If the current patterns persist, it is anticipated that North and South America will undergo a process of separation. A landmass is anticipated to detach off the eastern coastline of Africa. Australia is projected to undergo a shift towards closer proximity with the Asian continent.

Comparison of Different Theories

Continental Drift – See Floor Spreading – Plate Tectonics
Continental Drift – See Floor Spreading – Plate Tectonics


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