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Mountain Building
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Mountains are defined as steep
sided hill more than 600 m high.
Another phenomenon remarkably explained by the
plate tectonic theory is the formation of mountains
on the earth’s surface.
The process of mountain formation is called
orogenesis.
Four kinds of mountains have been observed on
the earth’s surface.
1. Fold mountains
2. Block mountains
3. Volcanic mountains
4. Dome mountains
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Fold mountains consists of great masses of
folded sedimentary rocks whose thickness is
often as much as about 12 km.
Folds are buckling of once horizontal rock
strata, caused by rocks being crumpled at plate
boundaries
The deformation of the layers of rocks is
known as folding
After compression, if the limbs of the
resultant fold are inclined in opposite
direction, the fold is called an anticline
After compression, if the limbs of the
resultant fold are inclined in the same
direction, the fold is called a syncline
anticline forms a hill or mountain
syncline forms a valley or depression
rocks may undergo
several repeated cycles
of compression.
Under such conditions,
the rocks are intensely
deformed and complex
folds are produced.
Nearly all of the world’s fold mountains are found at convergent plate
boundaries.
The highest mountains are the ones which arise due to the collision of
two continental plates.
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Based on the age of the fold
mountain, they can be classified as:
old fold mountain and
 new fold mountain

•lower in height and
• have gentler slopes
•and rounded peaks
Aravallis
old fold mountains are found within a plate,
at a location which represents
an ancient plate boundary.
Appalachains
Himalayas
•Young fold mountains are
Characterized by their
•greater height,
•steeper slopes and
•sharp peaks.
•found at present plate boundaries,
•E.g. Himalayas, Alps, Andes
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Most mountain building occurs at convergent
plate boundaries.
Colliding plates provide the compression
forces that
fold,
fault,
and metamorphose the thick layers of
sediments deposited at the edges of
landmasses.

Ocean-Ocean Convergence
Ocean-ocean convergence mainly produces volcanic
mountains.

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Ocean-Continental Convergence
The types of mountains formed by ocean-continental
convergence are volcanic mountains and folded
mountains.
 An accretionary wedge is the accumulation of
different sedimentary and metamorphic rocks with
some scraps of ocean crust.

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Continental-Continental Convergence

At a convergent boundary between two plates
carrying continental crust, a collision between the
continental fragments will result and form folded
mountains.