Paleomagnetism and Geomagnetism
Paleomagnetism and Geomagnetism deal with the study of Earth's magnetic field and the presence of magnetic direction and dip in the fossilized rocks (solid rock) because both the direction and the dip give an idea of magnetic properties of the earth as well as the drifting of the continents.
Magnetic Direction in Rocks
The direction of metallic minerals in the rocks reveals the direction of the magnetic field whenever the rocks were formed. Since the magnetic field keeps on shifting and the south pole of the rocks gets attracted towards the geographical North Pole, we can understand the shifting of the continents.
Magnetic Dip and Intensity
The dip or angle tells about the strength or the intensity of the magnetic field. Since the intensity is greatest at the poles, the dip is perpendicular if a rock has solidified near the pole. On the other hand, if the rock has solidified near the equator, the angle is parallel to the magnetic field.
Polar Region Anomalies
The study of past magnetic properties of the rocks shows that there are some parts of the world which today are near the polar region but have parallel magnetic dip. This means that those places were once near the equator and have drifted to their present position.
Rocks in North Europe show parallel magnetic dip despite being in polar regions today, indicating they were once near the equator.
Indian Subcontinent
Rocks in India shows that older rocks have perpendicular dip while the recent/newer rocks have a parallel dip. Similarly the direction of rocks have also changed, indicating that India has drifted northward.
Magnetic Anomaly in Oceanic Crust
Similarly, the study of oceanic crust also reveals there is magnetic anomaly on the oceanic crust. Thus, the study of old rocks provides the biggest evidence of the dynamic nature in the arrangement of continents and oceans, and proves that drifting has taken place.
PALEO-CLIMATIC EVIDENCES
The study of past climate gives a better idea about the changes in climatic conditions because geomorphic processes leave their distinct imprint on the landforms-
The past climate has changed because the position of the continents was not constant and they have drifted from one climatic zone to another.
Carboniferous Glaciation Evidence
One of the biggest evidences is carboniferous glaciation in which Wegener prepared a map showing evidences of glaciation in the form of tillite deposit in Brazil, Falkland Island, Africa, Peninsular India, Australia and Antarctica.
Wegener suggested that these regions have glaciers or evidence of glaciers because during that time the South Pole was located near present-day Durban and all these continents were part of the Gondwana landmass and located near the South Pole. Therefore, the processes operating in this region were the processes that operate during glaciation.
Glaciated Features Found:
We have evidence of till deposits, glaciated fossils as well as some of the glaciated topography such as Arêtes, Cirques, etc.
Coal Distribution Evidence
Similarly, the present distribution of coal shows that most of the coal fields are located in Eurasia. Coal was formed in a period known as the Carboniferous period due to the death and decomposition of vegetation belonging to hot and humid climatic conditions.
This means that present-day Eurasia was across the equator or was present between 5° to 35°N during the Carboniferous period and has drifted further northward.
CONCLUSION
Though Wegener's theory had many flaws, the basic idea of Wegener that continents continuously changed their position led to serious thought and discussion about the drifting of the continents.
This eventually led to the study of Sea Floor Spreading, which ultimately resulted in the grand theory known as Plate Tectonic Theory.
Why This Topic is Important for UPSC
Paleomagnetism and Continental Drift form a crucial part of Physical Geography and are frequently asked in UPSC Prelims, Mains (GS-I) and State PCS examinations. Understanding these concepts is essential for topics like Plate Tectonics and Earth's Evolution.
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