neostencil.com – live online classroom for ias preparation ... · study from india’s best ias...
TRANSCRIPT
1
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
Plate Tectonics
In this article series, we have till now covered concepts like continental drifting,
seafloor spreading and convectional current theory which gives the explanation
for many geomorphological features present on the earth. But still, there remain
some unanswered questions like- how do the fold mountains form, what are the
causes behind the occurrence of earthquakes, what are the reasons behind
volcanic activity on land and so on. For answering these and other similar
questions, we will learn about a very important concept in this article, that is, the
theory of Plate Tectonics.
Formulation of the theory of plate tectonics
With the emergence of the concept of seafloor spreading, and wealth of new
evidence at the beginning of the 1950s and 1960s, the interest in the problem of
distributions of oceans and continents was revived. Also, the following six
developments were instrumental in the formulation of the theory of plate
tectonics:
Development of mid-oceanic ridges and sea floor spreading
Palaeomagnetism
The findings of the age of ocean floors
Discoveries of island arcs and submarine trenches
The precise documentation of volcanoes and earthquakes, identification of
susceptible seismic zones, and spots vulnerable to volcanic activity
Identification of hotspots, their strengths, size and retrospective ejections.
2
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
What is a ‘tectonic plate’, ‘plate tectonics’ and ‘tectonic activity’?
The Earth consists of four concentric layers: inner core, outer
core, mantle and crust. The crust and uppermost of solid mantle are known as
lithosphere. Whereas asthenosphere is highly viscous, mechanically weak
and semi-molten region of the upper mantle of the Earth. And, lithosphere floats
over asthenosphere.
Figure showing the structure of the earth
A tectonic plate is a massive, irregularly shaped slab of solid rock, generally
composed of both continental and oceanic lithosphere. Plates move horizontally
over the asthenosphere as rigid units.
On the basis of size, a tectonic plate may be a major plate or a minor plate. For
example, Pacific plate is a major plate whereas Nazca plate is a minor plate.
On the basis of nature, a plate may be referred to as continental plate or oceanic
plate depending on which of the two occupy a large portion of the plate. For
example, Pacific plate is mostly an oceanic plate whereas Eurasian plate may be
called as a continental plate.
3
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
While a tectonic plate is a rigid lithospheric slab, plate tectonics is a collective
term for evolution, nature and motion, deformation, the interaction of plate
margins and resultant landforms.
The earth’s crust is continuously experiencing movements in horizontal as well as
vertical direction resulting in breaking and bending of crustal rocks and this
process of deformation is known as the tectonic activity.
Theory of Plate Tectonics
The theory of plate tectonics proposes that the earth’s lithosphere is divided into
seven major and several minor plates. The movement of the plates results in the
building up of stresses within the plates and the continental rocks above, which
leads to folding, faulting and volcanic activity. The major plates are surrounded by
fold mountains, ridges, trenches and faults.
These plates have been moving very slowly across the globe throughout the
history of the earth. Moreover, it may be noted that all the plates without
exception, have moved in the geological past, and shall continue to move in the
future as well.
Alfred Wegener in his theory of continental drift had thought that continents
move, but, this is incorrect. He further believed that all continents were initially
existent as a super-continent, Pangea. However, later discoveries have revealed
that continental masses, resting on plates have been moving, and Pangea was a
result of the convergence of different continental masses that were part of one or
the other plates.
4
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
Figure showing seven major plates and some minor plates
The seven major plates are:
1. North American plate (with the western Atlantic floor separated from the South
American plate along the Caribbean islands)
2. South American plate (with western Atlantic floor separated from the North
American plate along the Caribbean islands)
3. Pacific plate
4. Antarctica and the surrounding oceanic plate
5. Eurasia and the adjacent oceanic platee)
6. Africa with the eastern Atlantic floor plate
7. India-Australia-New Zealand plate
5
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
While Pacific plate is the largest of them all, South American plate is the smallest.
Minor plates:
1. Carribbean Plate
2. Cocos Plate
3. Caroline Plate
4. Juan de Fuca Plate
5. Juan Fernandez micro Plate
6. Iranian Plate
7. South sandwich Plate
8. Myanmar Plate
9. Anatolian Plate
10. Nazca Plate
11. Nubian Plate
12. Philippines Plate
13. Okhotsk Plate
14. Scotian Plate
15. Eastern micro Plate
16. Somalian Plate
17. Arabian Plate
18. Solomon Plate
19. Fiji Plate
6
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
20. Bismarck Plate
The force behind the Movement of Plates
Previously, we have studied that intense heat is generated from the radioactive
decay of substances deep inside the Earth (the mantle) which creates magma
consisting of molten rocks, volatiles and dissolved gases. These produce
convectional currents when the magma, heat and gases seek a path to escape in
the mantle. The force behind the movement of the plates are these convectional
currents generated by the upwelling of hot magma which causes the overlying
lithospheric slabs to uplift and stretch.
Figure showing how convection currents play role in movement of plates
Rates of Plate Movement
The rate of plate movement is determined by the bands of normal and reverse
magnetic fields that parallel the mid-oceanic ridge. The rates of plate movement
have a considerable variation. For example, while the Arctic Ridge has the slowest
rate (less than 2.5 cm/yr), the East Pacific Rise in the South Pacific has the fastest
7
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
rate (more than 15 cm/yr). An interesting fact is that the movement of Indian
plate from south to equator was one of the fastest plate movements in history.
Importance of the theory of Plate Tectonics
For geologists, it is a fundamental principle for study. It is the unifying theory of
geology, which further explains large-scale geological phenomena, such as
earthquakes, volcanoes, and the existence of ocean basins and continents.
Plate tectonics theory explains why there are lots of volcanoes in Iceland and
Japan, but far fewer in Russia and Africa. This is because Iceland was created by
a mid-oceanic ridge. Similarly, Japan is located on a fault line. The constant
pressure around the fault line causes many earthquakes and volcanic eruptions.
For geographers, the theory of Plate tectonics aids in the interpretation of
landforms. It ultimately explains why and where deformation of Earth’s surface
occurs.
Further, the concept of plate tectonics explains mineralogy. New minerals pour
up from the core along with the magmatic ejections. The plate boundaries
are the pathways through which rocks from the mantle come out as deposits on
lithosphere. These rocks are the source of many minerals. The famous Pacific
Ring of fire known for its violent volcanic activity is also a ring of mineral
deposits.
8
NeoStencil – Live Online Classes - IAS/IES/GATE/SSC/PSC | +91 95990 75552 | [email protected]
Study from India’s Best IAS Teachers LIVE Online
NeoStencil is India's number 1 platform for LIVE online learning. We help you connect with India's best teachers from the comfort of your home.
Some of our popular UPSC Civil Services Exam courses:
UPSC General Studies Foundation Courses offered at NeoStencil
1. Lukmaan IAS 2. Pavan Kumar IAS 3. Destination IAS 4. Toppers 25
UPSC Mains Optional Subjects courses
Pub Ad :S. Ansari, Pavan Kumar, Atul Lohiya (Hindi Medium) Philosophy :Mitrapal Geography :Prof. Majid Husain, Alok Ranjan (English and Hindi Medium), Md. Rizwan Sociology :Praveen Kishore, Vikash RanjanVenkata Mohan, Mujtaba Husain Anthro :Venkata Mohan History :Alok Jha PSIR : Kailash Mishra (English and Hindi Medium), RS. Sharma Law : Dinesh Verma (Scope IAS)
General Studies Mains Test Series:Pavan Kumar IAS, Lukmaan IAS, AAI IAS Pub Ad Test Series :Pavan Kumar Sociology Test Series :Praveen Kishore, Venkata Mohan, Lukmaan IAS Geography Test Series :Prof. Majid Husain, Alok Ranjan (English and Hindi) , Lukmaan IAS Anthro Test Series :Venkata Mohan Essay Test Series :Lukmaan IAS, Venkata Mohan
Current Affairs Online Courses for IAS Exam Preparation
1. Lukmaan IAS 2. Venkata Mohan 3. Mk Yadav 4. Alok Jha
We also Provide Online courses for IES | GATE | SSC | State PCS Exams. For more details visit
our All Courses Page – here