A geosyncline means a water depression characterized by sedimentation. It has now been accepted by majority of the geologists and geographers that all the mountains have come out of the geosynclines and the rocks of the mountains originated as sediments were deposited and later on consolidated in sinking seas, now known as geosynclines.
Geosynclines are the area of long, wide, and shallow depression of the water body bordered by rigid masses and get huge sedimentation deposition from surrounding areas.
Examples of Geosynclines
Tethys Sea in Asia, the Appalachian geosynclines in N. America, and the Caledonian geosynclines in Great Britain are examples of geosynclines.
Shape of Geosynclines
Geosynclines are long but narrow and shallow water depressions characterized by sedimentation and subsidence. Geosynclines are much longer than their widths.
Stages of Geosynclines
The geosynclinal history is divided into three stages viz.:
(i) Lithogenesis (the stage of creation of geosynclines, sedimentation and subsidence of the beds of geosynclines.
(ii) Orogeneis (the stage of squeezing and folding of geosynclinal sediments into mountain ranges)
(iii) Gliptogenesis (the stage of gradual rise of mountains, and their denudation and consequent lowering of their heights).
Geosynclinal Orogen Theory of Kober
German geologist Kober has presented a detailed and systematic description of the surface features of the earth. His main objective was to establish a relationship between ancient rigid masses or tablelands and more mobile zones or geosynclines, which he called orogen.
- Kober not only attempted to explain the origin of the mountains on the basis of his geosynclinal theory but he also attempted to elaborate the various aspects of mountain building e.g., formation of mountains, their geological history, and evolution, and development.
- He considered the old rigid masses as the foundation stones of the present continents. According to him present continents have grown out of rigid massess. He defined the process of mountain building or orogenesis as that process which links rigid masse with geosynclines. In other words, mountains are formed from the geosynclines due to the impacts of rigid masses.
- Kober’s geosynclinal theory is based on the forces of contraction produced by the cooling of the earth. He believes in the contraction history of the earth.
- According to him, the force of contraction generated due to the cooling of the earth causes horizontal movements of the rigid masses or forelands which squeeze, buckle and fold the sediments into mountain ranges.
Questions
Q. What is a geosyncline?
a) A linear fold in the earth’s crust
b) A large depression in the earth’s crust filled with sedimentary rocks
c) A volcanic eruption
d) A type of earthquake fault
Answer: b)
Explanation: According to Kober’s geosyncline theory, a geosyncline is a large depression in the earth’s crust that accumulates sedimentary rocks over time. The depression is formed due to the subsidence of the earth’s crust under the weight of sedimentary rocks. The geosyncline theory explains the formation of mountain ranges due to the upward folding and faulting of the sedimentary rocks within the geosyncline.
Q. Which of the following processes does not occur in a geosyncline?
a) Sedimentation
b) Folding
c) Volcanism
d) Uplift
Answer: c) Volcanism
Explanation: According to Kober’s geosyncline theory, volcanism does not occur in a geosyncline. Instead, sedimentary rocks accumulate in the depression, which then undergoes folding and uplift to form mountain ranges
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