The document discusses plate tectonics and describes the key components: - There are different types of tectonic plates that make up the lithosphere and move over Earth's mantle. - Plates move through divergent boundaries where new seafloor is created, convergent boundaries where plates collide, and transform boundaries where plates slide past each other. - The movement of plates causes geological features like mid-ocean ridges, volcanic island arcs, and mountain ranges to form.

1. Kaustubh J. Sane
HJD Institute of Technical
Education & Research

2.  Theory of plate tectonics
 Types of plates
 Causes of plate motion
 Importance of plate tectonics

3.  Wegener’s continental drift hypothesis stated that the
continents had once been joined to form a single
supercontinent.
 Wegener proposed that the supercontinent, Pangaea,
began to break apart 200 million years ago and form the
present landmasses.

7.  According to the plate tectonics theory, the uppermost
mantle, along with the overlying crust, behaves as a strong,
rigid layer. This layer is known as the lithosphere.
 There are two types of lithosphere
 Oceanic lithosphere
 Continental lithosphere

8. Continental Crust
 Thick (10-50 km)
 Old (>200 m.y. and up to 3.5 b.y.)
 Iron Poor (<1%) /
Silica Rich (>70%)
 Less Dense (~ 2.5 g/cm3)
 High Rising
(mostly above see level)
 Formed at Convergent Plate
Boundaries
Oceanic Crust
– Thin (<10 km)
– Young (<200 my)
– Iron Rich (~5%) /
Silica Poor (~50%)
– Dense (s.g. ~3 x H2O)
– Low lying (5-11 km deep)
– Formed at Divergent Plate
Boundaries

11.  Types of plate boundaries
 Depending on the motion of the plate they are grouped
into 3 major types viz,
1. Divergent plate (constructive plate boundary)
2. Convergent plate ( destructive plate boundary)
3. Transform plate

12. Click here for a hyperlink to an animation of convection
Be sure to click the play button!

13. o Plates are moving away from each other
o Midocean ridges are created and new ocean
floor plates are created.
o The plate gives birth to new earth surface
hence it is also called as constructive plate
boundary.
o As new material comes on surface mostly in
sea and increases the sea floor hence it is
called as sea floor spreading.

14. • Oceanic ridges are continuous elevated zones on the floor of
all major ocean basins. The rifts at the crest of ridges represent
divergent plate boundaries.
• Rift valleys are deep faulted structures found along the axes of
divergent plate boundaries. They can develop on the seafloor or
on land.

15. Can you explain this diagram!?

16. The place where two plates move
apart or diverge is called a divergent
boundary.

17. This is a model of sea floor spreading at a divergent boundary called
a mid ocean ridge.

18. Did you know that the Earth’s longest mountain range is underwater and
is called the mid-ocean ridge?
: www.ocean.udel.edu
The Mid-Ocean Ridge system, shown above snaking its way
between the continents, is more than 56,000 kilometers (35,000 mi)
long. It circles the earth like the stitching on a baseball!

19.  A subduction zone occurs when one oceanic plate is
forced down into the mantle beneath a second plate
 Oceanic-Continental
• Denser oceanic slab sinks into the asthenosphere.
• Pockets of magma develop and rise.
• Continental volcanic arcs form in part by volcanic activity
caused by the subduction of oceanic lithosphere beneath a
continent.
• Examples include the Andes, Cascades, and the Sierra
Nevadas.

21. • Two oceanic slabs converge and one descends
beneath the other.
 Oceanic-Oceanic
• This kind of boundary often forms volcanoes on the
ocean floor.
• Volcanic island arcs form as volcanoes emerge
from the sea.
• Examples include the Aleutian, Mariana, and
Tonga islands.

23. • When subducting plates contain continental
material, two continents collide.
 Continental-Continental
• This kind of boundary can produce new mountain
ranges, such as the Himalayas.

24. Also the way the Appalachian Mountains formed

25. from: http://www.geo.lsa.umich.edu/~crlb/COURSES/270
Continental crust to continental crust
collision
India-Asia (Himalayas)
Before collision
After collision

26.  At a transform fault boundary, plates grind past
each other without destroying the lithosphere.
 Transform faults
• Most join two segments of a mid-ocean ridge.
• At the time of formation, they roughly parallel the
direction of plate movement.
• They aid the movement of oceanic crustal material.

28. A transform boundary is a place where two plates slip
past each other, moving in opposite directions.

29.  The plates may move in opposite directions
or in the same directions but at different rates
and frequent earthquakes are created
(example: San Andreas Fault)