The surface of the Earth contains many heights and depressions . Present ridges are generally seen in the forms of a single mountain , single mountain ranges and mountainous landmasses.
There have been many hypotheses concerning the origin of these ridges and how they have been created , however , volcanic rocks have often played a role in their creation . The common point of all of hypothesis presented is that these heights have been formed following some movements which have affected the structure of the Earth's crust and created dislocation in its layers . In other words,the movements caused a dislocation in the original condition of the layers of the Earth.Following these movements rocky layers at the bottom of the seas , lakes and on the surface of the Earth which are almost horizontal,lose their original shape,move up and down,crush and sometime break,and finally make heights on the surface of the Earth. Perhops the oldest hypothesis concerning the appearance of the mountains is that the Earth gradaally began to cool after its formation; following the compression resulted from such a cooling process,some folds were created on the surface of the Earth. It seems that this hypothesis is unable to explaine the present orogeny )the process of mountain formation). Another hypothesis states that the heat inside the Earth,which is much more than that of its surface,causes the Earth to expand and as a result cracks its surface . The pieces thus produced give rise to heights and depressions on the surface of the Earth. This process occurs on the basis of isostasic equilibrium ) an equilibrium relationship among different parts of the Earth ).
Some other hypotheses state that all orgenic activities must have been and is accompanied by volcanic activities . These lava create ridges on the surface of the Earth.
According to Geosynclinal hypothesis most mountains were created in the margin regions which used to be the site of condensed and continous sedimentations . In addition to the weight of sediments,such phenomenon as suction in convective movements and lateral pressures give rise to the depression of these areas in million of years time.Such a process repeats many times in the course of time.According to isostasic equilibrium a movement in the opposite direction of the depression is created and gives rise to heights and mountains.
Studies carried on in recent decades have considered another theory . Studies and investigations performed indicate that the upper layer of the Earth ) Lithosphere ( is made up of a number of plates which move slowly on their lower layer )Asthenosphere) in such a way that the course of their relative movement is approximately a few centimeters in a year ) plate techtonic theory (.On the basis of this theory the plates which are adjacent to each other act in the forms of divergence ) Divergent Boundaries ( , convergence ) Convergent Boundaries (,or vibration.In the divergent case lava penetrate to the upper layer and make it swell.There are two other cases which generally create lateral pressure,folds,and heights on the surface of the Earth.
In summary,the factors responsible for the change in the equilibrium of the Earth's ( solid ( crust such as changes in the temperature of the Earth , volcanoes, earthquakes,solar radiations and the change in the speed of the Earth's rotation,each have had some suggestions and propositions as to how mountains were created.It must be kept in mind that most of the propositions presented have been founded on the basis of different processes happening in the depths of the Earth and most of them are mere theories.None of these theories have so far been able to answer all the questions posed in connection with the formation of mountains