Distribution of Oceans and Continents - Chapter 4 Geography NCERT Class 11
Summary
TLDRThis educational video explores the distribution of oceans and continents, highlighting the theories of continental drift by Alfred Wegener and seafloor spreading by Harry Hess. It explains how Earth's surface, once a single landmass, has dramatically changed due to forces like convection currents and plate tectonics. The video also delves into the evidence supporting these theories, such as matching coastlines and the distribution of fossils, and discusses the movement of the Indian plate, contributing to the formation of the Himalayas.
Takeaways
- 🌍 Earth's surface is 71% ocean and 29% land, earning it the nickname 'Blue Planet'.
- 🌱 The distribution of oceans and continents has changed significantly over time, with continents once forming a single landmass.
- 📜 The theory of continental drift, proposed by Alfred Wegener, suggested that continents were once joined and have since drifted apart.
- 🔍 Evidence for continental drift includes matching coastlines, similar rock ages, and the distribution of fossils and Placer deposits.
- 🌀 The concept of convection currents in the Earth's mantle was proposed by Arthur Holmes, providing a mechanism for continental movement.
- 🌋 The mapping of the ocean floor revealed underwater mountains, trenches, and mid-ocean ridges, adding new dimensions to the study of Earth's structure.
- 🌌 The seafloor spreading theory, proposed by Harry Hess, suggested that new oceanic crust is formed at mid-ocean ridges and pushes older crust aside.
- 🏔 The formation of the Himalayas is a result of the convergent boundary between the Indian and Eurasian plates, where one plate is pushed under another.
- 🔮 The theory of plate tectonics, which unifies the concepts of continental drift and seafloor spreading, explains the movement of Earth's lithosphere.
- 📏 The movement of tectonic plates is measured in millimeters per year, with the forces driving this movement originating from the Earth's mantle.
Q & A
What percentage of Earth's surface is covered by oceans?
-71% of Earth's surface is covered by oceans.
Why is Earth sometimes referred to as the 'Blue Planet'?
-Earth is referred to as the 'Blue Planet' due to the abundant water on its surface, which covers 71% of the planet.
What was the initial observation that led to the theory of continental drift?
-The initial observation was the similarity in coastlines on either side of the Atlantic Ocean, which suggested that they were once joined together.
Who proposed the theory of continental drift?
-The theory of continental drift was proposed by a German meteorologist named Alfred Wegener.
What were the two forces suggested by Alfred Wegener as reasons for continental drift?
-Alfred Wegener suggested that the forces behind continental drift were 'pole fleeing force' and 'tidal force'.
Why was Wegener's theory of continental drift initially rejected?
-Wegener's theory was initially rejected because the forces he proposed were considered inadequate to cause the continents to drift.
What was the major contribution of Arthur Holmes to the understanding of Earth's structure?
-Arthur Holmes proposed the concept of convection currents operating in the Earth's mantle, which became a basis for rejecting the continental drift theory.
What is the significance of mid-ocean ridges?
-Mid-ocean ridges are long chains of underwater mountains formed due to volcanic eruptions and are significant as they provide evidence for seafloor spreading.
How did the mapping of the ocean floor contribute to the understanding of continental drift?
-Mapping of the ocean floor revealed that it has a similar uneven surface to landmasses, with mountain ranges and deep trenches, which provided new evidence against Wegener's theory.
What is the concept of seafloor spreading?
-Seafloor spreading is the concept that new oceanic crust is formed at mid-ocean ridges through volcanic activity, and this crust then moves away from the ridges as new material emerges.
What is plate tectonics and how does it relate to the distribution of oceans and continents?
-Plate tectonics is the theory that Earth's lithosphere is divided into several plates which move over the mantle. This movement of plates explains the distribution of oceans and continents and the processes of continental drift.
What are the three types of plate boundaries?
-The three types of plate boundaries are divergent boundaries, where plates move apart; convergent boundaries, where plates move towards each other; and transform boundaries, where plates slide past each other.
How are the movements of the Indian plate described?
-The Indian plate initially broke away from the Australian plate and moved northwards towards the Eurasian plate, leading to the formation of the Himalayas due to convergent movements.
Outlines
🌏 Overview of Earth's Oceans and Continents
The video begins by highlighting that Earth's surface is 71% ocean and 29% continent, earning it the nickname 'Blue Planet'. It introduces the concept that the current distribution of land and water was not always the case, and that understanding how and why these changes occurred is crucial. The video promises to delve into the theories and evidence gathered by scientists and philosophers to explain Earth's structure, starting with the theory of continental drift.
🌍 Continental Drift Theory
The script discusses the theory of continental drift, which suggests that continents were once joined and have since drifted apart. It credits Dutch mapmaker Abraham Ortelius for the initial observation and German meteorologist Alfred Wegener for formulating the theory in 1912. Wegener proposed that continents were drifting due to 'pole fleeing force' and 'tidal force', although these reasons were later deemed inadequate, leading to the theory's rejection. The video also mentions a separate video on the evidence supporting continental drift.
🔍 Post-Drift Studies and Seafloor Mapping
Post-drift studies, following the rejection of Wegener's theory, explored further using ocean floor mapping. This new research revealed that the ocean floor is not flat but has a varied terrain, including mountain ranges and deep trenches. Scientists discovered mid-ocean ridges formed by volcanic eruptions and found that rocks from these ridges were younger than those from continental areas. These findings provided new evidence that contributed to a better understanding of Earth's dynamics.
🌐 Plate Tectonics and Earth's Movement
The script introduces the concept of plate tectonics, which suggests that the Earth's lithosphere is divided into plates that move. It explains the three types of plate boundaries: divergent, where plates move apart; convergent, where plates move towards each other; and transform, where plates slide past each other. The video also discusses how scientists measure the rate of plate movement and the forces behind it, such as convection currents in the mantle.
🏔️ Formation of the Himalayas and Indian Plate Movement
This section details the movement of the Indian plate, its separation from the Australian plate, and its convergence with the Eurasian plate, leading to the formation of the Himalayas. It discusses the geological events that occurred as the Indian plate moved, including volcanic eruptions that formed the Deccan Traps. The script also describes the current position of the Indian plate and its interactions with other plates, emphasizing the dynamic nature of Earth's crust.
📚 Conclusion and Educational Summary
The video concludes by summarizing the three key theories discussed: continental drift, seafloor spreading, and plate tectonics. It emphasizes that plate tectonics is now the widely accepted theory for explaining the distribution of oceans and continents. The script invites viewers to explore more educational content and subscribe for updates, highlighting the importance of understanding Earth's geological processes.
Mindmap
Keywords
💡Continental Drift
💡Pole Fleeing Force
💡Tidal Force
💡Convection Current Theory
💡Mantle
💡Mid-Oceanic Ridges
💡Sea Floor Spreading
💡Plate Tectonics
💡Divergent Boundaries
💡Convergent Boundaries
💡Transform Boundaries
Highlights
Continents cover 29% of Earth's surface, while oceans cover 71%, earning Earth the nickname 'Blue Planet'.
The distribution of oceans and continents has changed significantly over time.
Continental drift theory suggests that continents were once joined and have since drifted apart.
Alfred Wegener proposed the continental drift theory in 1912, suggesting continents are moving.
Pole fleeing force and tidal force were Wegener's initial reasons for continental drift, but were later deemed inadequate.
Post-drift studies introduced new evidence from ocean floor mapping, challenging earlier theories.
Convection current theory, proposed by Arthur Holmes in 1930, suggests mantle convection as a driving force for continental movement.
Ocean floor mapping revealed underwater mountain ranges, deep trenches, and other geological features.
Mid-ocean ridges are formed by volcanic eruptions and are the longest mountain chains on Earth.
Rock samples from mid-ocean ridges are younger than those from continental areas, indicating recent volcanic activity.
Ocean floor is divided into continental margins, abyssal plains, and mid-ocean ridges based on depth and relief.
The distribution of earthquakes and volcanoes correlates with plate movements and is evident in the ocean floor.
Sea floor spreading is a key concept that explains how new oceanic crust is formed and how it affects continental drift.
Plate tectonics theory, introduced in 1967, suggests that the Earth's lithosphere is divided into plates that move.
There are seven major and several minor plates that make up the Earth's lithosphere.
Plate movements are categorized into three types: divergent, convergent, and transform boundaries.
The movement of plates is driven by convection currents in the Earth's mantle.
The Indian plate's movement and its impact on the formation of the Himalayas is a significant example of plate tectonics in action.
The chapter concludes with a discussion on the three major theories that explain the distribution of oceans and continents.
Transcripts
in this video we're going to read about
the distribution of oceans and
continents today continents cover 29% of
the total surface of the Earth and the
rest that is 71% is covered by ocean
bodies that is the reason planet Earth
is also called as Blue Planet due to the
Abundant water on its surface when you
look at the world map the distribution
of ocean bodies and land mass how they
are today it was not like this earlier
it was something like this so in this
chapter we will understand how why and
what made them change so much that it
changed from the picture on your left to
the picture on your right we will also
learn how scientists came to know about
this because scientists and philosophers
are the ones who formed theories and
collected evidence regarding the
structure of the earth therefore it gets
very fascinating to know about their way
and methods of coming to a conclusion
which everyone of us today are reading
about let's begin with the first topic
continental drift Contin Al drift is a
theory based on the fact that if you
look at the coastline of both side of
Atlantic Ocean which is these two places
basically you will see some similarity
it looks as if they were together as one
land mass once upon a time and then it
broke apart and because of this
observation scientists believed that the
two American continents then Europe and
Africa they were once joined together
initially there was this Dutch map maker
Abraham atius who came up with this
observation about the three continent
being together but in 1912 it was a
German meteorologist by the name of
Alfred Wagner who gave a comprehensive
argument in the form of continental
drift theory because he thought that the
continents are drifting away from each
other I've made a separate video on this
topic the theory of continental drift
and the evidence in support of this
Theory you can find both the videos Link
in the description please have a look at
it so far we have studied about what is
the continental drift theory and what
are the evidences in support of the
continental drift theory now we are
going to read about the forces behind
continental drift theory Alfred Wagner
the person who suggested the theory of
continental drift he suggested that
there were two reasons behind it first
one is pole fleeing force and the second
one is tidal Force let me tell you in
quick what these two forces are by the
name pole fleeing Force we can think of
something that is fleeing away or
running away from the pole in this case
we are talking about the land mass that
is fleeing away from the South Pole
because in initially it was considered
that Pang was originated near South Pole
and the Earth's centrifugal forces
caused Pang to break apart and the
resultant continents to drift towards
Equator the second force that was
suggested by Vaga was the tidal force it
is due to the attraction of the Moon and
the Sun that develops tide in Oceanic
water so WEA believ that it is due to
these two forces that worked for
millions of years led to Breaking of
continents now there is a Twist in this
Theory most Scholars considered these
forces to be totally inadequate meaning
they did not find enough strength in
these two reasons that was suggested by
wager which ultimately led to the
rejection of his theory so please
remember it is due to the invalid
reasons presented by vager led to the
rejection of his theory on Continental
Drift and those invalid reasons were
pole fleeing forces and tidal Force now
we are going to read about post drift
studies meaning after the rejection of
vean continental drift theory there were
some more research and studies done so
that it would be better to know that
what if there are some unknown Avenues
which were left unexplored now the
problem with vag's theory on Continental
Drift was the evidence which were
completely focused towards landmass in
fact they were collected from landmasses
so if you remember from the video
evidence in support of continental drift
theory Again the video link is in the
description we spoke about distribution
of fossils of Flor and FAA or deposits
like Delite so all these evidences were
focused towards landmar now Alfred
Wagner proposed his theory on
continental drift in 1915 that was the
time of World War I a number of
discoveries during the post-war period
added new information to geological
literature particularly The information
collected from Ocean flow mapping
provided New Dimensions for the study of
distribution of oceans and
continents now let's read about what are
those new information that came out the
first one is convectional current theory
now what is the meaning of the word
convectional convection is the circular
motion that happens when warmer air or
liquid which has faster moving molecules
making it less dense Rises while the
cooler air or liquid drops down so how
does rainfall occur when warm air that
goes up it holds a lot of liquid
basically the moisture part and when it
condenses the warmer air is cooled the
mo moisture inside it it breaks into
liquid molecules and it falls down as
rain now in the similar sense there's
this person called Arthur Holmes in 1930
he said that there is a possibility of
convection current operating in the
mantle portion now if you remember
anything from the video different layers
of the earth there I have discussed that
the Earth is divided into these layers
right crust mantle and core and
especially mantle is divided into two
parts the upper mantle and lower mantle
and the upper mantle is also called as
asthenosphere which means weaker layer
so Arthur Holmes is basically saying
that there is a convection current which
is operating in this part of the earth
which is the upper mantle because here
all the rock is in molten State and
there is this motion going on wherein
the wherein the molten rock is moving in
a circular path and that is what makes
this layer very weak so Arthur Holmes
says that there exists a system of such
currents in the entire mantle potion so
this was a very major contribution to
our understanding of how the earth works
and this also became the basis on which
the Contemporary scientists discarded
the continental drift theory so I hope
you understood the convectional current
theory now we're going to read about
mapping of the ocean floor by the very
name you can understand that it speaks
about mapping or exploring the ocean bed
so while mapping the scientists found
that ocean floor is not just a vast
plane but it is full of relief meaning
it has similar uneven surface like we
have on landmar there are mountain
ranges as well as deep trenches and then
deep valleys in the ocean bed so
trenches are deep cavity or crack in the
ocean bed they usually occur when two
continental plates move apart there's
another thing called the mid Oceanic
ridges ridges are long mountain ranges
now imagine how there could be a long
mountain range inside the ocean and the
reason behind that is due to volcanic
eruptions so always remember right under
the crust we have the mantle mantle is
again of two types that is upper and
lower mantle but this mantle consists of
molten rocks that keeps circulating that
is why the mantle is not a stable layer
of the Earth so whenever there is a
volcanic eruption the magma comes out of
the oceanic crust it then becomes
solidified Rock after cooling this
solidified rock is also known as oceanic
crust and this oceanic crust after
repetition forms Oceanic rich rich
bridge is an uplifted land mass that
looks like a mountain range so what the
scientists did was they took samples of
rock particles from this Ridge area as
well as from the Continental area they
just wanted to experiment and see
whether which one of them is younger in
terms of age and it turned out that the
sample of rocks that were collected from
The Ridge area is younger and that has
to be obviously younger because the
volcanic eruption is happening every now
and then so newer molten rocks are
forming layers of oceanic crust and this
was an interesting finding which made
the post- drift studies more real and
valid now we're going to read about
ocean flow configuration here the entire
ocean flow has been divided into three
segments and it has been done purely
based on the depth as well as relief
meaning based on the looks let's read
about each segment of the ocean floor
the first one is Continental margin by
The Heading you can again figure out
that it's talking about area between the
shore that is Continental Shore and deep
sea bessin
if you are on a beach as you go further
towards the sea you'll notice the land
form shows depression as a result the
water level increases like this there
will be a point where the water gets
really deep and from above it looks deep
blue that is the deep sea bessin so this
area is called the Continental margin
and this consists of continental shelf
continental slope which is the land
depression then continental rise and
deep Oceanic trenches again trenches
mean deep cavity which occur when two
continental plates move apart the second
one is Abyssal Plaines so Abyssal means
very very deep we are talking about deep
plains that lie between Continental
margin and mid Oceanic ridges so I have
explained you what is Continental margin
and what is mid Oceanic ridges so the
area in between is called the abysal
plane there's something special about
this place all these sediments that is
the mud or Rock particles it gets
deposited here so if you see there is
land depression as we move away from the
continent towards deep sea due to this
natural depression all the mud particles
or sediments it moves downwards it moves
towards the abysal plane and the third
component of ocean floor is mid Oceanic
ridges I've explained what they are they
are long chain of mountain system within
the ocean it is also the longest
mountain chain on Earth but it is inside
the ocean water and these rich occur due
to intense vol iic activity when the
magma comes out of the mantle it breaks
the oceanic crust so that the molten
rocks can come out and after cooling it
forms layers of crust this is how there
is an upliftment that makes it a rich
now we are going to read about the
distribution of earthquakes and
volcanoes for this we are going to refer
to this figure the big black dots
represent hot spots which basically
means that here the magma comes out of
the mantle that's why they are referred
to as Hotpot spots many such hotpots are
located in ocean floor and there are few
on Continental mass as well the next you
see the tiny black dots these are places
where you will find a volcano many of
them are located on Continental mass and
a few in ocean
floor then we have these tiny gray dots
forming a long line sort of a thing
these are regions of shallow earthquake
and they are found on Ocean bed they are
also known as mid Oceanic ridges and
I've explained what mid Oceanic rides
are they occur due to movement of
continental plates and if you see
earthquakes are Tremors originating from
plate
movements at last we have the gray
shaded regions they are deep earthquake
zone again they are part of mid Oceanic
ridges but these are deeper ones and a
very active earthquake zone so if you
look at the grish area near Indian
Himalayan region this region is very
unstable because the Indian and uian
plates are constantly converging and
creating tension so this this was the
entire distribution of earthquakes and
volcanoes that we saw with the help of a
figure now we go on to the topic concept
of seaf flow spreading now this is where
things get really interesting so you
remember Alfred Wagner's continental
drift theory in case you haven't seen
the video I recommend you do so the
video link is in the description or you
can also click on the info card on top
vag's Theory focused more on the
Continental evidence like the fossils of
animals found in various Continental
landmasters then how the South American
east East Coast kind of looked like a
missing puzzle when joined with the
African West Coast so things like that
were Alfred Wan's arguments now what
happens is the post- drift studies gave
some valid arguments and information
against Wagner's continental drift
theory especially mapping of the ocean
floor and testing of oceanic rocks were
very crucial steps that were taken by
the scientists they revealed some real
facts that gave the post- drift study
good amount of weight when compared to
Wagner's continental drift theory I know
things are getting a little confused
using so what I'm going to do is create
a nice differentiation between both the
theories side by side so that it makes
clear sense as to what is what and it
will also serve as a quick revision so
on your left hand side is the
continental drift theory given by Alfred
Vagner and on your right hand side is
the post- drift studies which were done
by various scientists just to prove the
point that there are reasons much more
Beyond What wagonner
suggests the continental drift theory
talks about the matching of continents
Wagner said if you look at South America
and Africa they look like a jigsaw
puzzle fit when brought closer which is
true that once upon a time both land
masses were together but the reason
behind that is much more deeper than
just merely looking at the world map and
saying they were ones together the
second point in continental drift theory
talks about the fact that rocks from
different continents were of the same
age and this point made Vaga believe
that the land masses were once together
and they slowly drifted away again the
reason behind the drifting is much
deeper than just looking at rocks and
saying they all are same the third point
in continental drift theory talks about
tillite formation the Gana land consists
of six land masses they are India Africa
Madagascar Australia Antarctica and
folkland Islands under the base of these
six land masses teite sediments were
found so that made Vaga think that okay
these six land masses were once together
and now they are aart so this is a
pretty good observation however the
reason is much bigger and in depth
rather than observing Delights
the fourth point in continental drift
theory talks about Placer deposits they
are deposits of Rich minerals like gold
diamonds Etc so if you look at the coast
of Ghana and then coast of Brazil you'll
see that these Placer deposits looks
like Wayne that were once joined
together this point again made vagona
believe that Africa and South America
was once a single landmar and the last
point in continental drift theory talks
about distribution of fossils when
identical species of plants and animals
were found on landmasses it made Vaga
strongly believe that once upon a time
there was only a single landmass and
with time it started splitting into
different continents so these were the
evidences of Alfred wager that made him
come up with the continental drift
theory now coming to the right hand side
that is the post drift studies after the
World War II many discoveries were made
which added new information scientists
started arguing the fact that Alfred
Vagner only looked at evidences that
were collected from the Continental
areas which is true if you look at the
left hand side all these evidences were
taken by simply looking at the land
masses so in the post- drift studies the
scientists felt hey why don't we do some
comprehensive study by mapping the ocean
floor and that led to the convectional
current theory where Arthur Holmes said
it is because of the magma present in
the mantle which is causing the ocean
flow to expand since the oceanic crust
is thinner than the continental crust
therefore it is easy for the magma to
come out from the ocean bed and that's
why the mid Oceanic ridges give a solid
proof about this Theory and the second
point in post- drift theory is the
mapping of ocean floor when the ocean
floor was being mapped scientists saw
that ocean bed is not a flat piece of
land it has similar terrain uneven
surface just like we have on land this
was an astonishing finding and then they
also went on to find mid Oceanic ridges
on the ocean bed which are these long
range of mountains that were formed due
to the rocks that came out of the mantle
in the form of magma and when scientists
took samples of rock from the mid
Oceanic ridges as well as from the
Continental side they found that the
rocks from the mid Oceanic Ridge were
comparatively younger in age hence they
concluded as we move away from the mid
Oceanic ridges the age of the Rocks
increases so this was the post- drift
studies which totally focused on the
concept of sea flow spreading that is
the ocean flow gets pushed to the
opposite side due to volcanic eruption
at the crest and making the sea flow
spread and it was presented by Harry hes
in
1961 whereas the continental drift
theory by Alfred Wagner focused on the
argument that all the continents were
once upon a time a single Continental
Mass named pangi and then the single
Continental Mass began to split into
smaller ones and that's how the world
looks today so if you see two totally
different theories proposed by two
different people hold on we are not done
yet now we have a third concept which
brings us to the topic plate
tectonics now this is the third concept
that tries to answer the questions
related to distribution of oceans and
continents if you see this entire
chapter so far has been trying to answer
the questions related to distribution of
ocean and continents I mean that's what
the title says and we have so far seen
two theories the concept of PL tectonics
was presented by mezi Parker and Morgan
three people in 1967 just after 6 years
of hess's SE floor spreading Theory so
what the plate tectonic Concepts say is
the lithosphere which is also the
combination of crust and upper manle it
is in the form of irregular slab of
solid rock so think of the lithosphere
as a large plate and now when a plate
breaks this is exactly what it looks
like when we say irregular slab of solid
rock this is what the plate tectonics
concept is
suggesting so we know that lithosphere
consists of crust and upper mantle and
the crust is both continent Al as well
as Oceanic in nature the oceanic crust
is thinner than Continental but in
general it is one complete crust hence
the lithosphere covers both ocean as
well as Land And now when we think of a
plate we can easily relate that a plate
consists of land as well as ocean
doesn't matter which of the two occupy a
larger portion of the plate now let's
look at the world map according to this
New Concept which is plate tectonics our
entire Earth surface is divided into
seven major and some minor plates and
the these major plates are the first one
is Antarctica and the surrounding
oceanic plate and the second one is
North American with Western Atlantic
flow separated from South American Plate
along the Caribbean islands plate the
third one is South American with Western
Atlantic floor spread it from the North
American Plate along the Caribbean
islands plate and the fourth one is
Pacific Plate and the fifth one is India
Australia New Zealand plate and the
sixth one is Africa with the Eastern
Atlantic floor plate
and the seventh one is uraia and the
adjacent oceanic plate now let's look at
some minor plates the first one is Cocos
plate which is between Central America
and Pacific Plate then we have nasca
plate that is between South America and
Pacific Plate and then we have Arabian
plate mostly the Saudi Arabian Landmark
then we have Philippine plate between
Asiatic and Pacific Plate and then we
have Caroline plate between the
Philippine and Indian plate north of new
guinia and the last one is Fuji plate
that is northeast of Australia now the
reason this plate tectonic theory is so
interesting is because it makes a very
important argument that continents do
not move in fact continents are part of
these plates and it is the plates that
has been moving throughout the history
of Earth and it will continue to do so
in the future as well I hope you're
getting what I'm trying to say so if you
remember Alfred wner said that initially
everything was one single land mass
named as Pang but it according to new
discoveries it is now believed that Pang
existed due to the convergent mechanism
of plates on which continents reside
convergent means coming closer now we're
going to read about three types of plate
boundaries the first one is divergent
boundaries the meaning of the word
Divergent is pulling away so plates that
moves apart from each other is due to
Divergent mechanism and it creates a
fault or depression which is known as
divergent boundaries places where plates
move away is also known as spreading SES
one such example is the Mid-Atlantic
Rich here the American Plate is
separated from Eurasian and African
plates the second one is convergent
boundaries now convergent is opposite of
Divergent meaning coming closer so what
happens when two plates come towards
each other one plate Dives under another
and it is usually the smaller plate that
converges under the bigger plate leaving
that land area a little uplifted so this
mechanism happens between an oceanic and
Continental plate then between two
oceanic plates and then finally between
two continental plates the third one is
transform boundaries in this mechanism
what happens is the motion of the plate
is horizontal or in other words here the
two plates slide past one another I mean
the best way to imagine is look at this
picture and see how the plates are
moving past one another now that we have
read about different plate movements
it's time to understand what is the rate
at which these plates move I don't know
whether you have seen this program that
used to come on Discovery called strip
the city in that they discussed in one
of the episodes how geologists find the
rate at which the plates are moving it
is very fascinating to see what they do
is they Place sensors all over the
regions to record movs of a plate they
use an instrument called creep meter it
monitors the slow surface displacement
of an active geologic fault in the earth
its objective is to record the tension
that's building up in the Falls they put
two rods attached with steel wire so
when the Surface starts moving it puts
the wire and the geologist measure that
expanding Gap it's usually measured in
millim and roughly a fault moves around
5 to 10 mm a year I recommend you watch
that video in your free time it's really
fascinating we now come to another
important topic what is it that is
making these plates move I mean what is
that Force so when we see Earth we see
this round solid body floating in space
right but I want you to know this solid
body is not
motionless if you have seen my video on
different layers of Earth in that I have
explained the mantle consists of molten
rock and how this magma moves in a
circular manner making the upper mantle
a weak layer and from this weak layer
often heated material Rises to the
surface spreads and then sinks back
again this cycle keeps repeating over
and over to generate what scientists
call a convection cell or convective
flow again you can go back and look at
the convectional current theory that we
discussed under post drift studies so to
answer the question what is the force
that is moving the these plates the
answer is it is the soft mantle and the
circular flow of heated material inside
the earth which is the driving force
behind the plate movement coming to the
last topic of this chapter movement of
the Indian plate okay let me just
quickly wrap up this topic in the most
shortest and simplest form look at this
picture it's the movement of Indian
plate so initially India was part of
this huge Australian plate it was like
India was a large island situated of the
Australian coast and this Australian
plate was part of the Gana land we are
talking about 200 million years ago then
India broke from the Australian plate
and started moving upwards towards the
euroian plate about 40 to 50 million
years ago Himalayas started forming and
it is due to convergent mechanism we
have read about this when two plates
come closer a rapid uplift of land
surface takes place that's how Himalaya
came up before all of this in between
India and Eurasian plate there was the
tetis Sea and the Tibetan block while
moving up upfor roughly around 60
million years ago the Indian plate faced
some events like outpouring of lava and
that's how the decken Trap were formed
and you'll find all ignas rock there so
ignas rock is formed from solidified
lava that's how we are sure of the
volcanic eruption that happened on the
Indian subcontinent the Indian plate
includes Peninsula India and the
Australian Continental portions and then
if you see the Indian plate the
northeastern side it extends through
Rakin yomo mountains of Myanmar towards
the island Ark along the Java trench so
if you see the northeastern side is
going inside of the uran plate a little
bit and on the western side we have the
Arabian plate which extends up to the
Red Sea and then if you go to the
southern part the Antarctica plate so
you can see the oceanic Ridge which is a
divergent boundary it is connected to
the Indian plate so it's kind of a nice
mapping system when you look at these
plates how they are well connected with
each other so anyways that was all about
the movement of the Indian plate so
basically in this chapter we discussed
about three important theories that
shape the reason behind the distribution
of oceans and continents they are
continental drift theory by Alfred wner
then concept of seaf flow spreading
which is referred to as post- drift
theory proposed by Harry hes and then
finally the concept of play tectonics
presented by McKenzie Parker and Morgan
which is now well accepted Theory when
it comes to the reason behind the
distribution of oceans and continents
with this we have come to an end of this
chapter question answer can be found on
the website link is there in the
description thanks for watching and I'll
see you in the next one if you want to
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