Landform theories

Question 1

Plate Tectonics: intro?

Answer 1

Plate tectonics is a scientific theory that explains how major landforms are created as a result of Earth’s subterranean movements. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes.

the theory of plate tectonics is not related to any individual scientist, rather a host of scientists of various scientific disciplines and research groups and expeditions have contributed in the development of this valuable concept of the second half of the 20th century. eg Mckenzie and Parker’s Paving stone hypothesis; in 1965, J.T Wilson become first to suggest that the earth’s lithosphere is made up of individual plates and identified relative motion of plates and by 1968 the concept of Continental drift and sea-floor spreading were united to create an all encompassing theory known as plate tectonic.

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Question 2

Plate Tectonics: Headings?

Answer 2

1. Axioms
2. Plates
3. Plate Boundaries
4. Evidence
   4.1. Sea Floor Spreading
   4.2 Paleomagnetism
5. PT and Continental Displacement
6. PT and Creation of Oceans
7. PT and Mountain Building
8. PT and Vulcanicity
9. PT and Earthquakes
10. Criticism
11. PT vs Continental Drift

Question 3

Plate Tectonics: Axioms/Basic Postulates/ Assumptions?

Answer 3

Lithosphere is mobile and floating above denser but partially molten asthenosphere

Lithosphere is broken into amorphous pieces, larger and smaller known as major and minor plates

new material is generated by sea-floor spreading at the mid-ocean ridges

surface area is conserved, therefore plate material must be destroyed through another process

motion of plates is accomodated only along plate boundaries. The mobile plates are interacting along dynamic linear zones and geological processes are super active along such areas

Question 4

Plate Tectonics: Plates?

Answer 4

The lithosphere, 50-100km thick, is rigid and is broken up into seven very large continental- and ocean-sized plates, six or seven medium-sized regional plates, and several small ones.

A tectonic plate may be a continental plate or an oceanic plate, depending on which of the two occupies the larger portion of the plate.
The Pacific plate is largely an oceanic plate whereas the Eurasian plate is a continental plate.

The lithosphere rests on and slides over an underlying partially molten (and thus weaker but generally denser) layer of plastic partially molten rock known as the asthenosphere

Plate movement is possible because the lithosphere-asthenosphere boundary is a zone of detachment.

The lithosphere itself includes all the crust as well as the upper part of the mantle (i.e., the region directly beneath the Moho), which is also rigid. However, as temperatures increase with depth, the heat causes mantle rocks to lose their rigidity. This process begins at about 100 km (60 miles) below the surface. This change occurs within the mantle and defines the base of the lithosphere and the top of the asthenosphere. This upper portion of the mantle, which is known as the lithospheric mantle, has an average density of about 3.3 grams per cubic cm. The asthenosphere, which sits directly below the lithospheric mantle, is thought to be slightly denser at 3.4–4.4 grams per cubic cm

Question 5

Plate Tectonics: Plates: major plates?

Answer 5

Major Plates:

1. The Antarctic (and the surrounding oceanic) plate: continental core;
2. The North American plate: mostly continental with oceanic slab (NW Atlantic); moving W; riding over Juan de Fuca minor plate
3. The South American plate: mostly continental with oceanic slab of south Atlantic Ocean; moving W; riding over NAZCA plate
4. The Pacific plate: It is entirely oceanic and moving in NW direction and is subducting below Eurasian and Indo-Australian Plate
5. The India-Australia-New Zealand plate: largely oceanic; moving in N-NE direction and is subducting below Eurasian Landmass
6. The Africa with the eastern Atlantic floor plate: mostly continental; moving NE and subducting below Eurasian Landmass
7. Eurasia and the adjacent oceanic plate: moving in easterly direction; mostly continental though western part is oceanic

Young Fold Mountain ridges, oceanic trenches, and/or transform faults surround the major plates.

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Question 6

Plate Tectonics: Plates: minor plates? sub plates?

Answer 6

Minor Plates: Some important minor plates include:

1. Cocos plate: Between Central America and Pacific plate
2. Nazca plate: Between South America and Pacific plate
3. Arabian plate: Mostly the Saudi Arabian landmass
4. Philippine plate: Between the Asiatic and Pacific plate
5. Caroline plate: Between the Philippine and Indian plate (North of New Guinea)
6. Fuji plate: North-east of Australia
7. Juan De Fuca plate: South-East of North American Plate

Sub plates: (In the process, of development as a plate)are the china sub plate, Somalian, Arabian, Persian Sub plate.

Question 7

Plate Tectonics: Plates: Indian Plate?

Answer 7

The Indian plate includes Peninsular India and the Australian continental portions.

The Indian plate is one of the major plates whose northern boundary lies along the axis joining the northern flank of the peninsular plateau i.e. Rajmahal hills, Chota Nagpur, Baghelkhand, Bundelkhand, Malwa plateau and Aravalli hills. Its western boundary lies in the Arabian Sea by the Carlsberg Sea Ridge – 1752 m deep, the Indian Ocean by the Mid-Indian Sea Ridge – 2067 m deep and the southern boundary by the South-East Indian Sea Ridge in the Indian Ocean – 3017 m deep and the eastern boundary by the New Zealand Islands. And the Karmadic Ridge (located in the north-east of New Zealand) and the north-eastern border is located along the line joining New Guinea, Java, Sumatra and Andaman Islands

In the east, it extends through Rakim Yoma Mountains of Myanmar towards the island arc along the Java Trench. The Western margin follows Kirthar Mountain of Pakistan. It further extends along the Makrana coast of Balochistan and joins the spreading site from the Red Sea rift southeastward along the Chagos Archipelago.

The boundary between India and the Antarctic plate is also marked by an oceanic ridge (divergent boundary) running in roughly West to East direction and merging into the spreading site, a little south of New Zealand.

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After breaking away from gondwana, the Indian plate moved away @ 12cm/yr. As it approached the eurasian plate the sediments deposited in the Tethys sea was folded to form Himalaya mountains.

The Indian plate first collided with Eurasian plate near Ldakh which slowed down its motion.At the same time its rotation direction also changed. On hitting Ldakh the Indian plate started closing like a door. Today it’s flow speed has decreased to 5cm/yr.

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Question 8

Plate Tectonics: Plate Margins?

Answer 8

Three types:
1. constructive or Divergent plate boundaries
2. Destructive or Convergent Plate boundaries
3. Conservative or Shear or Transform plate Boundaries

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Question 9

Plate Tectonics: Plate Margins: constructive or Divergent plate boundaries?

Answer 9

Along Such Boundaries, high energy flow from the interior has been found which is suggestive of the rising limb of convectional currents.

It is a linear mobile Zone of sea floor spreading.

Divergence takes place in continental as well as oceanic plates, in oceans MOR (mid oceanic Ridge) and on continents great rift valleys are formed.

As plates move apart at a divergent plate boundary, the release of pressure produces partial melting of the underlying mantle. This molten material, known as magma, is basaltic in composition and is buoyant. As a result, it wells up from below and cools close to the surface to generate new crust. Because new crust is formed, divergent margins are also called constructive margins

Divergence and creation of oceanic crust are accompanied by much volcanic activity and by many shallow earthquakes as the crust repeatedly rifts, heals, and rifts again. Brittle earthquake-prone rocks occur only in the shallow crust. Deep earthquakes, in contrast, occur less frequently, due to the high heat flow in the mantle rock. These regions of oceanic crust are swollen with heat and so are elevated by 2 to 3 km (1.2 to 1.9 miles) above the surrounding seafloor.

Divergent movement of plates results in (i) volcanic activity of fissure flow of basaltic magma, (ii) creation of new oceanic crusts, (iii) formation of submarine mountain ridges and rises, (iv) creation of transform faults, (v) occurrence of shallow focus earthquakes, (vi) drifting of oceanic plates etc.

On a global scale, these ridges form an interconnected system of undersea “mountains” that are about 65,000 km (40,000 miles) in length and are called oceanic ridges.

Question 10

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries?

Answer 10

This is also known ‘Subduction zone’ or the ‘Zone of collision’ or ‘The Benioff Zone’

it is the Zone of maximum and most complex geological processes.

Events like volcanism, Earthquake, fold mts, deep trenches, are associated with these of boundaries.

Process:

1. When two plates collide, the denser plate is subducted below the lighter one because lesser the density greater the buoyancy.
   If the density is similar the plate with greater velocity will Be subducted. If the plates have similar velocity and density, then the older and the rigid plate subducts.
2. Because oceanic crust cools as it ages, it eventually becomes denser than the younger oceanic crust or continental crust, and so it has a tendency to subduct, or dive under, adjacent continental plates or younger sections of oceanic crust.
3. The plate subducts at an angle of 45 degrees, when it enters the asthenosphere (the margin of subducting plate)
4. At a depth of 100 km to 300 km, the partial melting begins and differentiation of magma takes place but silica has upward mobility and the differentiated magma begins to rise. This is known as volcanic outpour.
5. The rising magma creates a vent or a fissure and appears on the surface as volcanic arc.
6. As the two plates further converges and the sedimentary material (only in case of C-C or O-C collisions) and the relief features of the subducting plate is scratched and gets deposited in the trench. Later on when the compressional force is increased these materials are squeezed, compressed, and folded leading to orgenesis. The mountain thus raised is known as tectonic arc.

Convergent movement of plates results in (i) occurrence of explosive type of volcanic eruptions, (ii) deep focii earthquakes, (iii) formation of folded moun- tains, island arcs and festoons, oceanic trenches etc.

Convergent plate Boundaries can be of three types

Question 11

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: three types: O-O?

Answer 11

1. Ocean-Ocean collision:

(i) older oceanic crust having relatively denser material is subducted into upper mantle.

(ii) Such collision and subduction occurs along east Asia. The mighty Pacific plate subducts beneath the smaller, less-dense Philippine plate.

(iii) the resultant tectonic expression of plate collision and subduction includes deformation in crustal area, vulcanism, metamorphism, formation of oceanic trenches, island arcs and festoons etc., and occurrence of earthquakes

(iv) Trench indicate the zone of subduction. eg. Kuril trench, Japan trench, Philipines trench.

(v) volcanic arc is represented by Kuril is., Japanese Is., Philippines

(v) Back arc basin (explained in later f/c): eg. sea of Okhotsk, Japan sea, East China sea, South China sea etc.

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Question 12

Plate Tectonics: Plate Margins: Conservative or Shear or Transform plate Boundaries?

Answer 12

where two plates pass or slide past each other along transform faults. These are called conservative because crust is neither created nor destroyed.

The significant tectonic expression of such situation is the creation of transform faults which move, on an average, parallel to the direction of plate motion. Transform faults offset mid-oceanic ridges.
Besides oceanic transform faults, there are also continental transform faults e.g. San Andreas fault (California, USA), Alpine fault (Af rica) etc. It may be mentioned that San Andreas fault ‘is ridge to ridge transform fault.’

they don’t produce spectacular features like mountains or oceans, but the halting motion often triggers large earthquakes, such as the 1906 earthquake that devastated San Francisco.

In these areas of contact, stress is built which causes the rocks to break or slip, suddenly lurching the plates forward and causing earthquakes.
These areas of breakage or slippage are called faults. The border between the Pacific and North American Plates, a stretch of the Ring of Fire is a transform boundary.

The San Andreas Fault in California is an example of a transform boundary, where the Pacific Plate moves northward past the North American Plate.
It is one of the most active faults on the Ring of Fire.

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Question 13

Plate Tectonics: Plates: continental and Oceanic plates properties?

Answer 13

1. The continents have a crust that is broadly granitic in composition and, with a density of about 2.7 grams per cubic cm , is somewhat lighter than oceanic crust, which is basaltic (i.e., richer in iron and magnesium than granite) in composition and has a density of about 2.9 to 3 grams per cubic cm
2. Continental crust is typically 40 km (25 miles) thick, while oceanic crust is much thinner, averaging about 6 km (4 miles) in thickness
3. The distribution of these crustal types broadly coincides with the division into continents and ocean basins, although continental shelves, which are submerged, are underlain by continental crust.
4. their behaviour is only partly influenced by whether they carry oceans, continents, or both. The Pacific Plate, for example, is entirely oceanic, whereas the North American Plate is capped by continental crust in the west (the North American continent) and by oceanic crust in the east and extends under the Atlantic Ocean as far as the Mid-Atlantic Ridge.

These crustal rocks both sit on top of the mantle, which is ultramafic in composition (i.e., very rich in magnesium and iron-bearing silicate minerals). The boundary between the crust (continental or oceanic) and the underlying mantle is known as the Mohorovičić discontinuity (also called Moho)

The effect of the different densities of lithospheric rock can be seen in the different average elevations of continental and oceanic crust. The less-dense continental crust has greater buoyancy, causing it to float much higher in the mantle.

Question 14

Plate Tectonics: Plate Margins: constructive or Divergent plate boundaries: Process?

Answer 14

Process of sea floor spreading i.e. when divergence is under oceanic crust:

1. The convectional currents when rises, it pushes hot plume of magma from about 700 km of depth
2. this hot magma and energy is involved in a process called intra crustal thinning which is simply the gradual but regular melting of crustal material.
3. When the crust is weak enough, the lateral flow of convectional current beds crack into the oceanic slab. Eventually, the plates are horizontally displaced and sea-floor spreading begins.
4. The best-known example of divergent boundaries is the Mid-Atlantic Ridge
5. The fissure gradually widens and the magma pours out which gets deposited along trailing edges of the plate. The huge deposition creates mountainous ridges
6. It is along the trailing slabs, where the magma clings on and newer plates are created, thus it is also called the constructive boundaries. The rift valley is found in the central parts of the ridge, which signifies the tensional forces.
7. Since the magma comes from the asthenosphere it is peridotitic but when it comes on the surface due to magmatic differentiation becomes basaltic. Hence the new oceanic crust is basaltic.

Process of Continental Rifting i.e. when divergence is under continental crust

1. Upwelling of magma causes the overlying lithosphere to uplift and stretch
2. If the diverging plates are capped by continental crust, fractures develop that are invaded by the ascending magma, prying the continents farther apart. Settling of the continental blocks creates a rift valley, such as the present-day East African Rift Valley. If the plates there continue to diverge, millions of years from now eastern Africa will split from the continent to form a new landmass.
3. As the rift continues to widen, the continental crust becomes progressively thinner until separation of the plates is achieved and a new ocean is created. The ascending partial melt cools and crystallizes to form new crust. Because the partial melt is basaltic in composition, the new crust is oceanic, and an ocean ridge develops along the site of the former continental rift. Consequently, diverging plate boundaries, even if they originate within continents, eventually come to lie in ocean basins of their own making.

Question 15

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: Subduction zone?

Answer 15

The subduction process involves the descent into the mantle of a slab of cold hydrated oceanic lithosphere about 100 km (60 miles) thick that carries a relatively thin cap of oceanic sediments.

The path of descent is defined by numerous earthquakes along a plane that is typically inclined between 30° and 60° into the mantle and is called the Wadati-Benioff zone. The factors that govern the dip of the subduction zone are not fully understood, but they probably include the age and thickness of the subducting oceanic lithosphere and the rate of plate convergence.

EQs and the seismic activity extends 300 to 700 km (200 to 400 miles) below the surface, implying that the subducted crust retains some rigidity to this depth. At greater depths the subducted plate is partially recycled into the mantle.

The site of subduction is marked by a deep trench, between 5 and 11 km (3 and 7 miles) deep, that is produced by frictional drag between the plates as the descending plate bends before it subducts.

Question 16

Plate Tectonics: Plate Margins: Divergent Margins: aid to write answer?

Answer 16

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Question 17

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: back arc basins? sea anchor?

Answer 17

back-arc basin, are submarine basin that forms behind an island arc.

Such basins are typically found along the western margin of the Pacific Ocean near the convergence of two tectonic plates. Examples of back-arc basins include the Sea of Japan, the Kuril Basin in the Sea of Okhotsk, the Mariana Trough in the Philippine Sea, and the South Fiji Basin.

Back-arc basins are sites of significant hydrothermal activity, and the deep-sea vents that occur in these regions often harbour diverse biological communities.

Back-arc basins were initially an unexpected phenomenon in plate tectonics, as convergent boundaries were expected to universally be zones of compression

Process:

A back-arc basin is formed by the process of back-arc spreading, which begins when one tectonic plate subducts under (underthrusts) another. Subduction creates a trench between the two plates and melts the mantle IN THE OVERLYING PLATE, which causes magma to rise toward the surface.

Rising magma increases the pressure at the top of the overlying plate that creates rifts in the crust above and causes the volcanoes on the island arc to erupt. As additional magma breaks through the cracks in the crust, one or more spreading centres develop, which widen the seafloor and expand the section of the overlying plate behind the trench. (Spreading centres that form in back-arc basins are much shorter than those found along oceanic ridges, however.)

As the basin expands, the leading edge of the overlying plate may be forced oceanward, causing the trench to “roll back” (The backward motion of the subduction zone relative to the motion of the plate which is being subducted is called trench rollback ) over the subducting plate, or it may serve as a “sea anchor” by remaining fixed in place relative to the top of the subducting plate. In the latter case, the enlargement of the basin forces the trailing part of the overlying plate to move in the opposite direction.

Question 18

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: three types: O-C ?

Answer 18

Ocean-Continent collision:

(i) the greater buoyancy of continental crust prevents it from sinking, and the oceanic plate is preferentially subducted.

(ii) Continents are preferentially preserved in this manner relative to oceanic crust, which is continuously recycled into the mantle. This explains why ocean floor rocks are generally less than 200 million years old whereas the oldest continental rocks are more than 4 billion years old.

(iii) resultant tectonic expressions are deformation of crustal rocks, metamorphism, volcanic eruptions, formation of folded mountains and occurrence of deep-focus earthquakes.

(iv) Collision of American and Pacific plates is a typical example of this category and formation of majestic western cordillera of N. America and Andes of S. America is significant resultant tectonic expression of such situation.

(v) It may be mentioned that one of the manifestions of continent-oceanic plate collision is the exposure of deep ocean rocks through their thrusting in resultant mountain masses. This process is called obduction which is opposite to subduction

(vi) further the sediments also get accumulated in trench and later folded to form tectonic arcs (folded mts). eg. O-C collision is represented by Nazca plate and S. American plate. The trench is represented by Peru-Chile trench. The tectonic arc is represented by Andes mts. The volcanic arc is represented by Ojas Del Salado volcano on Argentina-Chile border, Cotopaxi and Chimborazo volcano in Ecuador etc.

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Question 19

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: three types: C-C?

Answer 19

Continent-Continent Collision:

(i) Two plates carrying continental crust collide when the oceanic lithosphere between them has been eliminated.

(ii) responsible for creation of folded mountains and occurrences of earthquakes of varying magnitudes.

(iii)The collision of Asiatic-Indian plates, and European-African plates is typical example of such situation and the formations of Alpine and Himalayan mountainous chains are major manifestions

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Question 20

Plate Tectonics: Plate Margins: destructive or Convergent plate boundaries: Why no volcanic arcs are found in case of C-C collision?

Answer 20

A few possible factors:

1. First of all, volcanic and igneous rocks are found along Himalayas and Alps (refer Mid Continental belt volcanoes). These however were formed because of collision between Eurasian plate and oceanic crust below the Tethys sea at the forefront of the Indian Plate and Eurasian plate. Volcanic arcs must have existed as the oceanic crust under Tethys sea subducted under Eurasian plate, but as the Indian plate continued onward, some time later it collided with Eurasian plate and folded the sediments into fold mt that destroyed these volcanic arcs. Nevertheless, part of that volcanic arc indeed is visible now in the surface. No volcanic edifice have survived the cataclysm that give rise to the Himalayas, but the rocks that formed the arc are now known as the Dras Volcanics, a band of volcanic basalts and dacites outcrops that are part of the Indus suture zone. And that are thought to originate in the Mesozoic (from about 252 to 66 Ma ago) volcanic arc that existed in the Eurasia plate as a consequence of the subduction of the oceanic crust under the Tethys sea.
2. under C-C collision, both plates are buoyed in asthenosphere and neither subducts rather they fuse together along ‘suture zone’ like the one present in Himalayas. Since neither plate is subducted, no magma is formed, no upwelling and no volcanic arcs.
3. even if one of the continental plate is subducted, it does not have the moisture of the oceanic crust. Moisture of the oceanic crust is necessary as it is the release of this moisture at the depths of ~100km that decreases the melting point of the lithosphere subducted. Since continental plate lacks this moisture, its melting point does not decrease enough and it does not melt.
4. Even if some magma is formed, and it rises up, it rarely reaches the surface and cools down while subterranean forming volcanic intrinsic structures and igneous rock deposits. Remember that continental lithosphere is thicker than oceanic.

Question 21

Plate Tectonics: India-Madagascar rift?

Answer 21

According to American and Indian scientists of NASA, asteroids are the reason for the fission of the supercontinent Gondwanaland. A paper to this effect appeared in the January 1993 issue of the ‘Geology Journal’ of the United States, written by John R. Marshall and Hans Agarwal. The impact of a meteorite or asteroid falling on the Earth comes from the debris of asteroids found on the Earth’s crust, which is called Tillite.

The Madagascar plate experienced two major rifting events during the break-up of Gondwana. First, it separated from Africa about 160 Mya (million years ago), then from the Seychelles and India 66–90 Mya

According to scientists from the National Geophysics Research Institute (NGRI), Hyderabad, Madagascar was first physically associated with the Dharwad Protocontinent of India, which broke away from the Indian Plate about 140 million years ago. It reached its present position after about 60 million years after fragmentation. Until now, Madagascar has been considered a part of the continent of Africa. Before the fission, India and Madagascar were moving north at the rate of 4 cm per year. After fragmentation, the Indian plate collided with the Eurasian plate and formed the Karlsberg and Indian Ocean Ridges between the Madagascar minor plate and the Indian main plate, which are made of basalt on the composition plate edge. There are many evidences of the association of the Madagascar plate and the Indian plate to the Dharwad region in the past.

1. Correspondence in Geo-Magnetism data obtained from geo-satellites and geologic and tectonic investigations from the eastern and western sides of Madagascar.
2. Similarity in the geological structure of both.
3. Equivalence in the remains of shallow seas located near both.

Prior to the study by the Department of Geophysical Survey of India, Bangalore, geologists believed that the Indian plate was stable in its place. The reason for the origin of the Himalayas is the southward flow of the Eurasian Plate or the Angarland, but the Geophysics Survey of India, Bangalore and the Chinese Geophysical Survey, Beijing have indisputably verified that the Indian plate itself moves in the north-east direction by 5.5 cm per year. rate is increasing.

Question 22

Plate Tectonics: Geo-Environmental consequence of Indian Plate motion/ Evidence of Indian plate motion?

Answer 22

1. The rate of elevation of the Himalayan ranges of 1.2 mm per annum is proof that the the northern edge of the plate is tetconically active and due to the drift in the north-east direction of the Indian plate, The Himalayan ranges are rising due to the pressure generated by the movement.
2. Earthquakes of varying magnitude along the Himalayan region from the Pamir knot to the Arakanyoma confirm that the subducted portion of the northern edge of the Indian plate is reaching the asthenosphere and transforming into magma, which exerts pressure on the Himalayan structure. Due to which earthquakes occur on the Himalayas with the help of Main Boundary Thrust (MBT) and Main Central Thrust (MCT). The Garhwal earthquake is a vivid evidence of this.
3. According to the data obtained from the aeromagnetic survey, the depth of the depression in the upper and middle Gangetic plains is 8000-6000 m, the thickness of the depression becomes more near the Himalayan mountain range and decreases towards the south plateau. This indicates that due to the north-easterly flow of the Indian plate, its northern edge submerged in the Himalayas, forming a trench between the Himalayan range and the northern edge of the plateau, the depth of which was greater in the north. as a result, The sediments brought by the rivers to the depression got deposited in greater thickness in the northern edge.
4. Several landforms of the Konkan and Kannada coast indicate that they were formed as a result of uplift. This proves that the western coast of India (except for Kutch in Gujarat) has been uplifted in the geologic past.
5. Earlier India’s Dharwad (Karnataka), Madagascar and Africa were interconnected and India was on the equator in the south position than the present. After the fragmentation, Madagascar and Africa were separated from India and the land west of the India land was submerged, on which the water of the Indian Ocean spread which was called the Arabian Sea. It was during this fault that the Western Ghat Mountains of India were born and the equatorial forests of the submerged landmass were buried and converted into petroleum. The petroleum of ‘Bombay High’ situated in the Arabian Sea 80 km west of Bombay is the result of this.
6. The main coal field of India or ‘Koylanchal’, located along the eastern and southern edges of the Chotanagpur plateau, is also evidence that this area was also covered with equatorial forest. During the tectonic event of the Meghalaya plateau separating it from the Chotanagpur plateau along the Dawki fault, these vegetation got buried and converted into coal.
7. The study of fossilized coconut fruit found between the intertrap beds of Mohgaon kalan of Madhya Pradesh by palaeontologists by carbon-14 dating method shows that it is about 70 million years old of Tertiary age. This proves that at that time there were equatorial forests with coconut species in Madhya Pradesh, that is, Madhya Pradesh was on the equator. It is at its present latitudinal position due to plate tectonics.
8. At the time of the eruption of the Rajmahal lava, about 100 million years ago, India was 2250 km south of the current position. In other words, it was at 20° south latitudinal position because 1° latitude = 111 km. Kanyakumari, which is today located at 8°4’ north latitude, was at that time about 12° south latitude.
9. The shift in the geographic north and magnetic north of a place is called ‘magnetic flux’.
   Due to the flow of the plate, the magnetic flux of each place of each plate keeps on changing. For example, in 1970, the magnetic field of Allahabad was 1/2° West, which was decreasing at the rate of 1’ (1 minute) annually
10. The Bay of Bengal on the north-eastern edge of the Indian plate is subducted by substantial sedimentation by the Ganges-Brahmaputra river system. The proof of this is the vertical roots of Sundari tree found in the Ganges Delta at a depth of 15 m to 150 m above sea level (Fig. 3)!
11. The east coast of India is sinking down at a rate of 1.2 mm per year (Gardner GS - Physical Geogrophy page 443) due to the subsidence of the Bay of Bengal geodesic.
12. Magma is coming to the earth’s surface through cracks created by the subduction of the Bay of Bengal. The volcanoes of Andaman and Nicobar Islands confirm this. 10 April 1991 The volcano erupted on Ko Baren Island (Middle Andaman) is a vivid example in this context.
13. Before the origin of Shivalik, the Indobrahma river flowed from east to west along the southern mountain foot of the Himalayas and fell into the Arabian Sea. Due to plate tectonics, due to the rise of the Delhi water divide, the course of this river was changed which started falling in the Bay of Bengal and its abandoned part is still in the form of Ghaggar river in Haryana, whose water dries up in Talwara lake of Rajasthan during rainy season.
14. A borewell carried out by the Natural Oil and Gas Commission in the Parvatpad region of Shivalik revealed a fresh water lake about 1700 feet deep, which is actually the valley of the Indobrahma river, in which sufficient water is also found in the sandy sediment. This valley was raised by the movement in the north-east direction of the Indian plate, which gave rise to the Shivalik range.
15. When the landmass that is now the Indian subcontinent slammed into Asia about 50 million years ago, the oxygen in the world’s oceans increased, altering the conditions for life, scientists say (https://www.financialexpress.com/lifestyle/science/apart-from-rise-of-himalayas-what-happened-when-indian-plate-collided-with-eurasian-plate-in-pre-historic-era/1561513/)

due to plate tectonics, there will be another category in future from Terai to the south of Shivalik range. can come into existence. Rapid sedimentation is taking place in the Terai region by various rivers, where the sedimentation load is causing the downpour of the Terai region. Geologists have detected a fault at Devvand in Saharanpur district which is called Himalayan Front Fault. This is the result of the subsidence of the Terai belt.