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Making of Earth
Following theories have been proposed:
- Continental Drift Theory
It was given by Alfred Wegner in 1912.
The terrestrial land found on this Earth in the form of different continents was earlier a single land mass called as Pangea while the ocean was called as Panthla Sea. Pangea started breaking up due to gravitational force and tidal force and led to the formation of various continents.
Evidence to support this theory:
- Jigsaw fit – South America and Africa continent show similarity on its pacific coast
- Similarity of geographical features of Appalachian mountains and Britney peninsula
- Similarities of fossil species belonging to same biological group were found in different continents. For e.g. Same fossil was found in Australia, South America, and Africa
- Grooves study – The features of grooves were similar in Antarctica and South America
- The forces mentioned by Alfred Wegner were extremely weak as these forces cannot bring such a big drift
- The jigsaw fit was not applicable to all the parts of the continents especially to North America and North Europe
- Convection Current Theory
This theory was given by Arthur Holumes.
According to this theory the various relief features on the surface of the earth are being made due to the movement of thermal current in the Mantle part due to the temperature difference which led to the moving of the plates.
It was unable to explain the formation of various features like Himalayan Mountain, Ocean, and Rift Valley
- Sea Floor Spreading Theory
This theory was given by Robert Diat and Hess.
The volcanic eruptions took place in marine ecosystem (ridges). The ruptured lava extended which led to the spread of the ocean while the ocean boundary got consumed in the subduction zone.
Evidence to support this theory:
- Mid Ocean Ridges found in the Ocean
- The study of mid oceanic ridge of Atlantic Ocean in which the edge of the ocean floor on both sides of ridge have a similar pattern
- Magnetic Polarity was found similar on both sides of the ridge
It was only able to explain the sea bed topography while the terrestrial topography remains unexplained.
- Plate Tectonic Theory
This theory was given by W.J.Morgan and Mechansy
According to this theory there are 2 types of plates called as continental plate and oceanic plate. These plates float over ‘esthinosphere’ (upper part of mantle and lower part of crust). These plates have movement either parallel or against each other which led to the formation of various relief features on the surface of the earth and sea floor.
Evidence to support this theory:
It explained the formation of Mid Oceanic Ridge, Rift Valley, Block Mountain, Young fold Mountain, Volcanic Mountain
- The folded mountain of Australia was not being explained by this theory
- It could not explain why spreading of ridges occur generally in Atlantic Ocean while subduction was confined to Pacific Region
- It could not explain the double trench concept
Major Plates in the World
- Antarctica plate
- North American plate
- South American plate
- Pacific plate
- Indo-Australian-New Zealand plate
- African plate
- Eurasian plate
Due to the continuous influence of external and internal forces, the formation and deformation of landforms on the surface of the earth are continuous processes. The internal and external forces causing stresses and chemical action on earth materials and bringing about changes in the configuration of the surface of the earth are known as geomorphic processes.
The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth.
Glciers, Groundwater, running water, the wind, waves, currents are called geomorphic agents
Types of Movement
- Diastrophic Movement (slow in nature)
Diastrophic forces refer to forces generated by the movement of the solid material of the earth’s crust. All the processes that move, elevate or build portions of the earth’s crust come under diastrophism.
- Orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust.
- Epeirogenic processes involving uplift or warping of large parts of the earth’s crust.
- Earthquakes involving local relatively minor movements.
- Plate tectonics involving horizontal movements of crustal plates.
- Sudden Movement
Examples are Earthquakes and Volcanoes
Movement of Plates
Continental Plate is made up of Granite while Oceanic Plate is made up of Basalt. Therefore Oceanic Plates are heavier or have higher density than Continental Plates.
INTER PLATE MOVEMENT
Converging Plate Boundaries
In this, plate moves opposite in direction to each other
- Continental-Continental Plate Convergence
Folded Mountains are formed
E.g. Alps Mountain, Caucasian Mountain, Zagros Mountain, Hindukush Range, Himalayan Mountain, Arakayoma Range.
- No Volcanic activity takes place
- High intensity of earthquake occur in this region having a deep foci
- Continental-Oceanic Plate Convergence
Formation of Volcanic Mountain
E.g. Rocky Mountain, Andes Mountain
- Low intensity of earthquake
- High volcanic activity takes place
- Oceanic-Oceanic Plate Convergence
Leads to the formation of Trenches (since oceanic plates are of higher density than continental plates)
E.g. Mariana Trench
When continental plate moves over volcano of an ocean and due to the eruption of that volcano small island is formed. Those islands are being called as the hotspot island. E.g. Islands of Pacific Ocean
Diverging Plate Boundaries
In this, plate moves away from each other
- Oceanic-Oceanic Plate divergence
Formation of mid oceanic ridge
E.g. Mid Atlantic Ridge
- Continental-Continental Plate divergence
Formation of nascent sea
E.g. Red Sea
Transforming Plate Boundaries
In this, two plates move parallel to each other therefore it doesn’t form any landform but this area becomes prone to earthquakes. E.g. Californian Plate
INTRA PLATE MOVEMENT
Movement occur within the plate
- Formation of Block Mountain
When certain part of plate gets subducted, the remaining part that stands as it is forms Block Mountain.
E.g. Vindhyas and Satpura Range, Drakensberg Mountain
The subducted part in intra plate is called rift valley.
E.g. East Rift Valley and West Rift Valley in Africa
- Formation of Nascent Sea
E.g. Caspian Sea