Geomagnetism

Geomagnetism

Geomagnetism - The magnetic field associated with the Earth is called Geomagnetism. The Earth behaves like a huge magnet with north and south magnetic poles.

The Earth has an outer rocky mantle below which there is a liquid outer core which surrounds the solid centre.

It is considered that the motion of charges, i.e., Iron in the liquid part of the Earth's core created the magnetic field. The rotation of the Earth causes the motion of these charged particles, in addition to the heat rising from the Earth's central core results in the generation of convection current of molten material in the outer core. 

Motion of the ions ( Fe+) in this molten material would produce an electric current through the Earth's core that results in magnetic field around the Earth.

Paleo Magnetism - The historical study of the Earth's magnetism in rocks is known as Paleo magnetism. 

When Igneous magma crystallizes, the crystals of ferrous-magnetic minerals in the magma acquire stable magnetism which becomes frozen as the magma cools down. This acquired magnetism is called as 'Fossil magnetism'.

Such rocks will have ferro-magnetic minerals aligned in the same direction as that of geomagnetic field at the time of its consolidation.

Polar Wandering - When Paleo magnetic evidences for a given region was checked over a long period of time, a gradual change in the direction was detected. It shows that the position of magnetic poles has moved steadily over time. This movement is known as 'Polar Wandering'.

Magnetic field reversal - During the study of oceanic surface, some rocks pointed towards the north and some towards the south. It is inferred that the rocks did not change their polarity but it is the Earth's magnetic poles which reversed its polarity. It is known as Magnetic field reversal. 

Such reversal of magnetic field can be brought by reversal of convection currents in the outer core. it is expected that magnetic field reversal will happen every 100-300 thousand years.

Note - Earth's magnetic poles are almost aligned with Earth's Geographical poles.

Earth's magnetic poles will never along Equator wise since Earth rotates on vertical axis not on horizontal axis. It is always North-South or South-North.

Aurora - When electrically charged particles from solar winds interacts with the Earth's magnetic fields near the poles, it produces spectacular lights which are called as Auroras which are more clearly visible during the winters.

It is called 'Aurora Borealis' in the Northern hemisphere (North Pole) and 'Aurora Australis' in the Southern hemisphere (South Pole).

Previous Article - Volcanism

Next Article - Earthquake and Tsunami

Notes on other subjects

Ancient History

Medieval History

Modern History

Geography

Polity

Optional Notes

Public Administration

Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own. 

Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍