2. INTRODUCTION
• The continents cover 29% of the earths surface
and the remainder of it by the oceans.
• The positions of continents and the ocean bodies
have not been the same in the past.
3. THE CONTINENTAL DRIFT
THEORY
• Many scientists thought of the similarity between
the symmetry of the coastlines of the continents &
considered the possibility of joint continents.
• Alfred Wegener – a German meteorologist & polar
explorer who put forward the theory of
“Continental Drift”
• Study of maps led him to suppose that the
continents had been once joined. This super –
continent was named PANGAEA.
• Subsequently, these broke into various smaller
continents that exist today.
5. EVIDENCE IN SUPPORT OF
THE CONTITNETAL DRIFT
1) Apparent fit of the
continents
The coastlines of the
continents appear to
fit together like pieces
of puzzle.
2) Fossil Correlation
Identical fossils have
been found in the
either sides of the
ocean.
6. EVIDENCE IN SUPPORT OF THE
CONTITNETAL DRIFT (CONT.)
3) Rocks & Mountain
correlation
Identical rocks &
mountain structures
have been found on
either side of the ocean.
4) Paleoclimatic data
Coal has been found in
cold regions and glacial
evidence has been
found in warm regions.
7. FORCE FOR DRIFTING
(WEGENER)
• Wegener suggested these forces responsible for the
drifting of continents.
1) Polar – fleeing force:
Caused by the rotation of the earth.
2) Tidal force
Due to the attraction of the moon and the sun that
develops tides
3) Sun
• However, these forces were considered inadequate by
most scholars.
8. POST – DRIFT STUDIES
• A number of discoveries during the post – war period
added new information to this.
1) Convectional Current Theory
The core is radioactive and releases heat to the mantle
surrounding it.
The mantle floats on the core, so the mantle is directly
affected by the core.
The core’s radioactive energy causes the lower mantle
to get hot, less dense and rise.
The plastic basalt rock rises, cools and it falls back.
This is a convection current.
10. POST – DRIFT STUDIES
(CONT.)
2) Mapping of the ocean floor
Detailed research revealed that the ocean floor is
full of relief.
Expeditions to map the oceanic floor provided a
detailed picture such as the existence of
submerged mountain ranges & deep sea trenches.
11. OCEAN FLOOR
CONFIGURATION
• The ocean floor may be
segmented into three major
divisions based on the depth
as well as the forms of relief.
1) Continental Margins
The continental margin is
the zone of the ocean floor
that separates the thin
oceanic crust from thick
continental crust.
Together, the continental
shelf, continental slope, and
continental rise are called
the continental margin.
12. OCEAN FLOOR
CONFIGURATION (CONT.)
2) Abyssal Plains
Extensive plains that lie
between continental
margins & mid – oceanic
ridges.
3) Mid – Oceanic ridges
Interconnected chain of
mountain system within
the ocean.
Has a rift at the centre &
is a zone for intense
volcanic activity.
14. SEA – FLOOR SPREADING
• The concept was first proposed by Harry Hess in the
1960s.
• Sea – floor spreading occurs when:
1) Magma rises to the surface & pushing the existing
sea floor away from the ridges.
2) The colder denser materials sink pulling the sea floor
away from the ocean ridge.
3) This way, new oceanic crust is created.
4) The plate then, when subducts, this crust is
destroyed where it melts & comes out of volcanoes
or is recycled back to a new oceanic crust.
15. EVIDENCE FOR SEA –
FLOOR SPREADING
• The rocks equidistant on either side of the mid –
oceanic ridges show remarkable similarities.
• The age of the rock increases as one moves away
from the crest.
• The ocean crust rocks are much younger than the
continental rocks.
• The sediments on the ocean floor are unexpectedly
very thin.
• The deep trenches have deep – seated earthquake
occurrences while in the mid – oceanic ridge areas, the
quake foci have shallow depths.
17. PLATE TECTONIC THEORY
• Plate Tectonic theory states that the Earth’s outer
mechanical layer, the lithosphere is divided into
large continent – sized plates that are constantly
moving.
18. PLATE TECTONICS
• In 1967, McKenzie & Parker came up with this idea.
• Tectonic plate → a massive, irregularly shaped rock.
• Generally composed of both continental & oceanic
lithosphere.
• Floats on the asthenosphere.
• Thickness range varies from:
1) Oceanic → 5 – 100 km
2) Continental → 200 km
• Maybe referred to as a continental or oceanic plate
depending on which occupies the larger portion.
19. PLATE TECTONICS (CONT.)
• These plates constantly move. Continents are a
part of the plate.
• 1 – 2 inches per year!
• There are three types of plate boundaries:
1) Divergent boundaries
2) Convergent boundaries
3) Transform boundaries
20. SOME MAJOR PLATES
1) Antarctica & the surrounding oceanic plate
2) North American plate
3) South America
4) Pacific plate
5) India – Australia – New Zealand plate
6) African plate
7) Eurasian plate
21. SOME MINOR PLATES
1) Cocos plate
2) Nazca plate
3) Arabian plate
4) Philippine plate
5) Caroline plate
6) Fuji plate
23. 1. DIVERGENT BOUNDARIES
• New crust is generated
as plates pull away from
each other.
• The site where the
plates move away from
each other is called
spreading sites.
• Continent → Rift valley
• Ocean → Mid – oceanic
ridge.
• Eg: Mid – Atlantic ridge,
African Rift valley
24. 2. CONVERGENT
BOUNDARIES
• Where the crust is
destroyed as one plate
dives under another.
• The location where it
occurs → Subduction zone
• Three ways:
1) Between an oceanic &
continental plate
2) Between two oceanic
plates
3) Between two continental
plates
25. 3. TRANSFORM
BOUNDARIES
• A transform boundary
occurs where two
plates grind past each
other without
destroying or
reproducing
lithosphere.
• Earthquakes
sometimes occur near
transform faults.
26. MOVEMENT OF INDIAN
PLATE
• The Indian plate includes
Peninsular India & the
Australian continental
portions.
• India was a large island
situated off the Australian
coast.
• India is supposed to have
started her journey some
200 mya.
• India collided with Asia
about 40 – 50 mya causing
rapid upliftment of land
(Himalayas)
Type Major
Approx. Area 11,900,000
km2
Movement North - East
Speed 26 – 36
mm/year
Features Himalayas,
Indian Ocean
