1
DAILY
CLASS NOTES
Physical Geography
Lecture – 08
Geomagnetism and Introduction
to Geomorphism
, 2
Geomagnetism and Introduction to Geomorphism
Earth's Geomagnetic Field:
❖ Geomagnetism is the study of the dynamics of the Earth's magnetic field, which is produced in the outer
core.
❖ The earth acts as a dipole magnet where the geomagnetic south pole is near the earth's geographic north
and vice versa.
❖ Approximately, it is the field of a magnetic dipole currently tilted at an angle of about 11 degrees concerning
Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth.
❖ The geomagnetic field is dynamic and it changes with location and time.
Geomagnetic Pole:
❖ The Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet
hypothetically placed at the center of the Earth.
❖ There is such a pole in each hemisphere, and the poles are called "the geomagnetic north pole" and "the
geomagnetic south pole", respectively.
❖ Approximately, the geomagnetic dipole is currently tilted at an angle of about 11 degrees to Earth's rotational
axis.
❖ On the other hand, the magnetic poles (the magnetic north pole and the magnetic south pole) are the points at
which magnetic needles become vertical.
❖ The difference in the position of magnetic poles and geomagnetic poles is due to the uneven and complex
distribution of the Earth's magnetic field.
❖ The geomagnetic poles are antipodal points where the axis of a best-fitting dipole intersects the surface
of Earth.
❖ In contrast, the magnetic poles of the actual Earth are not antipodal, that is, the line on which they lie does
not pass through Earth's center.
❖ If the Earth's magnetic field were a perfect dipole, the field lines would be vertical to the surface at the
Geomagnetic Poles, and they would coincide with the North and South magnetic poles.
❖ However, the approximation is imperfect, and so the Magnetic and Geomagnetic Poles lie some distance
apart.
Causes of Geomagnetic Field:
❖ The Magnetic Field of the Earth is generated by the motion of molten iron alloys in the Earth’s outer core.
❖ Differences in temperature, pressure, and composition within the core cause convection currents in the molten
metal.
❖ This flow of liquid iron generates electric currents, which in turn produce magnetic fields. This effect is known
as the Dynamo Effect.
Why are Geographic and Magnetic poles different?
❖ Geographic poles are fixed while Magnetic poles are wandering.
DAILY
CLASS NOTES
Physical Geography
Lecture – 08
Geomagnetism and Introduction
to Geomorphism
, 2
Geomagnetism and Introduction to Geomorphism
Earth's Geomagnetic Field:
❖ Geomagnetism is the study of the dynamics of the Earth's magnetic field, which is produced in the outer
core.
❖ The earth acts as a dipole magnet where the geomagnetic south pole is near the earth's geographic north
and vice versa.
❖ Approximately, it is the field of a magnetic dipole currently tilted at an angle of about 11 degrees concerning
Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth.
❖ The geomagnetic field is dynamic and it changes with location and time.
Geomagnetic Pole:
❖ The Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet
hypothetically placed at the center of the Earth.
❖ There is such a pole in each hemisphere, and the poles are called "the geomagnetic north pole" and "the
geomagnetic south pole", respectively.
❖ Approximately, the geomagnetic dipole is currently tilted at an angle of about 11 degrees to Earth's rotational
axis.
❖ On the other hand, the magnetic poles (the magnetic north pole and the magnetic south pole) are the points at
which magnetic needles become vertical.
❖ The difference in the position of magnetic poles and geomagnetic poles is due to the uneven and complex
distribution of the Earth's magnetic field.
❖ The geomagnetic poles are antipodal points where the axis of a best-fitting dipole intersects the surface
of Earth.
❖ In contrast, the magnetic poles of the actual Earth are not antipodal, that is, the line on which they lie does
not pass through Earth's center.
❖ If the Earth's magnetic field were a perfect dipole, the field lines would be vertical to the surface at the
Geomagnetic Poles, and they would coincide with the North and South magnetic poles.
❖ However, the approximation is imperfect, and so the Magnetic and Geomagnetic Poles lie some distance
apart.
Causes of Geomagnetic Field:
❖ The Magnetic Field of the Earth is generated by the motion of molten iron alloys in the Earth’s outer core.
❖ Differences in temperature, pressure, and composition within the core cause convection currents in the molten
metal.
❖ This flow of liquid iron generates electric currents, which in turn produce magnetic fields. This effect is known
as the Dynamo Effect.
Why are Geographic and Magnetic poles different?
❖ Geographic poles are fixed while Magnetic poles are wandering.
