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MOUNTAIN BUILDING AND SEA
FLOOR SPREADING
[Document subtitle]
, INDEX
S TOPICS Page No.
No.
1 Mountain Building 2-7
o Definition
o Forms of Mountains
o Classifications
2 Geosynclines 7-10
3 Theories of Mountain Building 10-20
4 Sea Floor Spreading 20-25
1. Mountain Building:
• Mountain building, also known as orogeny, is the process by which
mountains are formed when two tectonic plates collide and
converge.
A.) Forms of Mountain:
a) Mountain ridge: A system of long, narrow and high hills. Generally, the
slope of one side is of moderate slope but a ridge may also have
symmetrical slopes on both the sides.
b) Mountain Range: A system of mountain and hills having several ridges,
peaks and summits and valleys. It represents a long but narrow strip of
mountains and hills.
c) Mountain Chain: Consists of several parallel long and narrow mountains
of different period; sometime got separated by flat upland and plateaux.
d) Mountain System: Consists of different mountain ranges of same period
that are separated by valleys.
e) Mountain Group: Consists of several mountain groups and system.
f) Cordillera: A community of mountains having different ridges, ranges,
mountain chains and mountain system. The best example is mountainous
region of western part of North America.
B.)Classification of Mountains:
1. On the basis of Height:
i) Low Mountains; height ranges between 700 to 1000m
ii) Rough Mountains; height ranges between 1000m to 1500m
iii) Rugged Mountain; height ranges 1500 to 2000m
iv) High Mountain; height above 2000m
, 2. On the basis of Location:
i.) Continental Mountains: Coastal Mountains and inland
Mountains.
ii.) Oceanic Mountains
3. On the basis of Mode of origin:
i.) Original or tectonic mountains
a.) Folded Mountains- are further divided into 3 sub types on the basis of
their area. i.e., Young folded, mature folded and old folded mountains.
Folded mountains are one of the most prominent types of mountains on Earth,
formed by the process of folding due to the compressional forces within the
Earth’s crust. These mountains primarily develop along convergent plate
boundaries where tectonic plates collide, leading to the crumpling and uplift of
sedimentary rock layers.
• Formation Process
1. Accumulation of Sediments:
Sedimentary rocks are deposited over millions of years in geosynclines
(large, elongated depressions near plate boundaries).
These rocks often form in shallow seas or depressions, consisting of
layers of limestone, sandstone, and shale.
2. Tectonic Compression:
As tectonic plates converge, the accumulated sedimentary rocks are
subjected to intense compressional forces.
This compression causes the rock layers to buckle and fold, creating
upward folds (anticlines) and downward folds (synclines).
3. Mountain Building (Orogeny):
Over time, the folded structures rise to form mountain ranges.
The uplift process may also involve faulting, thrusting, and the intrusion of
igneous rocks.
4. Erosion and Modification:
After their formation, these mountains are gradually reshaped by erosion and
weathering, revealing their complex folded structures.
Characteristics
1. Structural Features:
Dominated by anticlines (upfolds) and synclines (downfolds).
MOUNTAIN BUILDING AND SEA
FLOOR SPREADING
[Document subtitle]
, INDEX
S TOPICS Page No.
No.
1 Mountain Building 2-7
o Definition
o Forms of Mountains
o Classifications
2 Geosynclines 7-10
3 Theories of Mountain Building 10-20
4 Sea Floor Spreading 20-25
1. Mountain Building:
• Mountain building, also known as orogeny, is the process by which
mountains are formed when two tectonic plates collide and
converge.
A.) Forms of Mountain:
a) Mountain ridge: A system of long, narrow and high hills. Generally, the
slope of one side is of moderate slope but a ridge may also have
symmetrical slopes on both the sides.
b) Mountain Range: A system of mountain and hills having several ridges,
peaks and summits and valleys. It represents a long but narrow strip of
mountains and hills.
c) Mountain Chain: Consists of several parallel long and narrow mountains
of different period; sometime got separated by flat upland and plateaux.
d) Mountain System: Consists of different mountain ranges of same period
that are separated by valleys.
e) Mountain Group: Consists of several mountain groups and system.
f) Cordillera: A community of mountains having different ridges, ranges,
mountain chains and mountain system. The best example is mountainous
region of western part of North America.
B.)Classification of Mountains:
1. On the basis of Height:
i) Low Mountains; height ranges between 700 to 1000m
ii) Rough Mountains; height ranges between 1000m to 1500m
iii) Rugged Mountain; height ranges 1500 to 2000m
iv) High Mountain; height above 2000m
, 2. On the basis of Location:
i.) Continental Mountains: Coastal Mountains and inland
Mountains.
ii.) Oceanic Mountains
3. On the basis of Mode of origin:
i.) Original or tectonic mountains
a.) Folded Mountains- are further divided into 3 sub types on the basis of
their area. i.e., Young folded, mature folded and old folded mountains.
Folded mountains are one of the most prominent types of mountains on Earth,
formed by the process of folding due to the compressional forces within the
Earth’s crust. These mountains primarily develop along convergent plate
boundaries where tectonic plates collide, leading to the crumpling and uplift of
sedimentary rock layers.
• Formation Process
1. Accumulation of Sediments:
Sedimentary rocks are deposited over millions of years in geosynclines
(large, elongated depressions near plate boundaries).
These rocks often form in shallow seas or depressions, consisting of
layers of limestone, sandstone, and shale.
2. Tectonic Compression:
As tectonic plates converge, the accumulated sedimentary rocks are
subjected to intense compressional forces.
This compression causes the rock layers to buckle and fold, creating
upward folds (anticlines) and downward folds (synclines).
3. Mountain Building (Orogeny):
Over time, the folded structures rise to form mountain ranges.
The uplift process may also involve faulting, thrusting, and the intrusion of
igneous rocks.
4. Erosion and Modification:
After their formation, these mountains are gradually reshaped by erosion and
weathering, revealing their complex folded structures.
Characteristics
1. Structural Features:
Dominated by anticlines (upfolds) and synclines (downfolds).
