Mountains form through intense deformation of the earth's crust from horizontal stresses and intrusion of molten rock. They are created through the process of orogenesis, which involves the accumulation of sediments in a subsiding geosyncline that are later compressed into folded mountains. Appalachian Mountains were formed in this way, with the geosynclinal theory of mountain building involving sedimentation, compression, deformation, uplift and erosion in a three-phase cycle. Mountains are classified geographically, structurally, and by their origins as folded, volcanic, fault-block, or upwarped mountains. Plateaus form from crustal deformation or volcanism and have high relief compared to plains, with economic uses including reservoirs,

1. Mountains
Most people think of a mountain as simply a high or more or less rugged landform , in contrast
to flat and low land. Mountain, however are much more than high country. To a geologist , the
mountain belt means long, linear zone in the earth’s crust where the rocks have been intensely
deformed by horizontal stresses and generally intruded by molten rock materials.
The topography can be high and rugged, or it can be worn down to a surface of low relief.
Orgenesis
The process of mountain building .
The factors that appear to be the most important in this process are:
Rock sequences - a set of rocks contained in a series of layers, used to interpret the paleoenvironment
over a period of time.
Geosyncline - the elongated subsiding trough.
Appalachian Mountain
-noted by James Hall (American geologist)
- Concluded that the present mountain ranges of Appalachian Mountain were once a region of
the crust that gradually subsided much more than the rest of the continent.
-The gradual subsided permitted that a great thickness of shallow-marine sediments to
accumulate at rates that were roughly equivalent to the ratio of subsidence.
- After receiving a critical thickness of sediments, the geosynclines were compress into folded
mountain range, which was uplifted and eroded.
The Geosynclinal Theory of mountain building
- Further developed by James Dana
- Proposed that mountain building involves the three-phase cycle:
Geosynclinal sedimentation and contemporaneous subsidence
Compression and deformation
Uplift and erosion
Structural Deformation

2. - deformed structure compression, in which the scale of deformation ranges from wrinkled
grains or fossils in the rocks to fold ten kilometers wide.
Deformation is most intense near continental margins, dying out toward the continental
interior.
Metamorphism
- refers to changes in the mineral composition and texture of rocks subjected to high
temperature and pressure within the earth.
Igneous activity
- concentration of the earth’s lighter material in the continental crust which takes place in the
two steps
1. Begins at a spreading center where partial melting of peridotite in the upper mantle
generates a basaltic magma , which rises to form oceanic crust
2. Involves a partial melting of oceanic crust forming a silica-rich magma, which then
emplaced in the mountain belt as granitic and andesitic volcanic products. Lighter
elements especially silicon and oxygen, are thus separated further in this process and
concentrated in the continental crust. The continental crust remain s at the surface of
the earth once it is formed.
3. Erosion and isostatic adjustment of the crust takes place after orogenesis and continues
until the mountain belt is eroded to near sea level
General Classification of Mountains
1. Geographically and chronologically, according to their arrangement
2. Structurally, according to their geological stratification.
Kinds of mountains
1. Folded mountains or complex mountain
- These result from folding of sedimentary or lava beds or may result from variable
resistance to erosion
Examples: Alps, Urals Himalayas and Appalachian mountain
2. Volcanic mountain – These result from the accumulation of lava and pyroclastics of volcanic
events

3. Examples Mount Apo, Mayon , and Taal . They may be volcanic plugs, conical layers, or
fragmented igneous materials around a central vent of Mayon in Albay, accumulation or
volcanic domes as Lassen Park in California, Mt. Vesuvius and Etna in Italy, Mt. Helen in USA and
Mt. Fujiyama in Japan.
Erosion volcanic mountains
- these are single mountains or a group of mountains that have been formed ny
the erosion of streams.
- Example: Sierra Madre
Individual mountain ranges are formed by one kind of diastrophic movement or volcanic
activity
The Sierra Madre Mountain Ranges of Eastern Luzon and the Cordillera Mountains in
Northern Luzon are collection of ranges known as cordillera.
3. Fault-block mountains
- These are mountains that are formed by the displacement of rock along the fault.
Examples: Mountain found in Basin and Range province, a region that
encompasses Nevada and portion of Utah, New Mexico, Arizona and California, and Marinduque
Mountains in the Philippines.
4. Upwarped mountains
These are produced in association with a broad arching of the crust or in some instances
because vertical displacement along high angle faults.
Examples: Black hills in Western South Dakota and the Adirondack mountains in
upstate New York.
Economic Value of mountains
 Poor farming areas ( due scarcity of soil, narrow valleys and cold climate)
 Humid slopes provide lush grasses for grazing
 Their streams provide water for irrigation and for electric power.
Plateaus
A plateaus is an extensive upland region .
Elevation of plateaus

4. Elevation of most plateaus of the world exceeds 2,000 ft. Height above the sea level, however, is not the
sole factor in classifying a land form as a plateau.
The Appalachian Plateau has an elevation of 3,000 ft. but….
The Great Plains, near the Rocky Mountains, have a maximum elevation of 6,000 ft.
Plain and plateau are different in relief. A plateau has high relief while a plain has a low relief.
Origin of Plateaus
Most plateaus region are the result of diastrophism.
Some are the result of Volcanism
In diastrophism, the two broadest kinds of deformation process are epligrogeny and
orogeny.
Epligrogeny involves the relative rose and fall of broad segment of the crust with little or no folding.
Some are the result of Volcanism
Youthful streams cuts gorges into this landform.
Hills are rounded and valleys are no longer V-shaped in mature plateaus.
Economic importance of Plateaus
 Dammed to impound the water in large reservoir. The stored water can be then use for
irrigation and generation of electricity.
 Some plateaus reveals ore deposits, like the Mexican plateaus which is rich in silver ores.
 Cold, dry climate of plateaus in tropical regions, Temperate crops can be grown
 In lowlands, tropical crop can be grown.
 In arid region, plateaus are used as pasture lands