Plate tectonics
-
Upload
kaustubh-sane -
Category
Education
-
view
195 -
download
0
Transcript of Plate tectonics
![Page 1: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/1.jpg)
Kaustubh J. Sane
HJD Institute of Technical Education & Research
![Page 2: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/2.jpg)
Theory of plate tectonics
Types of plates
Causes of plate motion
Importance of plate tectonics
![Page 3: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/3.jpg)
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.
![Page 4: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/4.jpg)
![Page 5: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/5.jpg)
![Page 6: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/6.jpg)
![Page 7: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/7.jpg)
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
![Page 8: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/8.jpg)
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
![Page 9: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/9.jpg)
![Page 10: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/10.jpg)
![Page 11: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/11.jpg)
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
![Page 12: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/12.jpg)
Click here for a hyperlink to an animation of convection
Be sure to click the play button!
![Page 13: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/13.jpg)
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.
![Page 14: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/14.jpg)
• 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.
![Page 15: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/15.jpg)
Can you explain this diagram!?
![Page 16: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/16.jpg)
The place where two plates move apart or diverge is called a divergent boundary.
![Page 17: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/17.jpg)
This is a model of sea floor spreading at a divergent boundary called
a mid ocean ridge.
![Page 18: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/18.jpg)
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!
![Page 19: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/19.jpg)
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.
![Page 20: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/20.jpg)
![Page 21: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/21.jpg)
• 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.
![Page 22: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/22.jpg)
![Page 23: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/23.jpg)
• When subducting plates contain continental material, two continents collide.
Continental-Continental
• This kind of boundary can produce new mountain ranges, such as the Himalayas.
![Page 24: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/24.jpg)
Also the way the Appalachian Mountains formed!
![Page 25: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/25.jpg)
from: http://www.geo.lsa.umich.edu/~crlb/COURSES/270
Continental crust to continental crust
collision
India-Asia (Himalayas)
Before collision
After collision
![Page 26: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/26.jpg)
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.
![Page 27: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/27.jpg)
![Page 28: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/28.jpg)
A transform boundary is a place where two plates slip past each other, moving in opposite directions.
![Page 29: Plate tectonics](https://reader036.fdocuments.in/reader036/viewer/2022081400/55575809d8b42aa8378b54a1/html5/thumbnails/29.jpg)
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)