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UPSC Prelims 2005 · World Geography · Rocks, Quakes and Landforms
Consider the following statements: Which of the statements given above is/are correct?
- The axis of the earth's magnetic field is inclined at 23 ½° to the geographic axis of the earth.
- The earth's magnetic pole in the northern hemisphere is located on a peninsula in northern Canada.
- Earth's magnetic equator passes through Thumba in South India.
- (a) 1, 2 and 3
- (b) 2 and 3
- (c) 2 only
- (d) 3 only
Show the answer and explanation
Answer: (d) 3 only
Only the Thumba magnetic-equator fact is right.
Statement by statement
1. ✗ WRONG The magnetic axis is tilted about 11°, not 23½° (that is the rotation axis tilt).
2. ✗ WRONG The north magnetic pole had moved off the Canadian peninsula into the Arctic Ocean by 2005.
3. ✓ CORRECT The magnetic equator passes near Thumba (Thiruvananthapuram) — why ISRO’s rocket station is there.
The idea
Geographic directions come from the rotation axis; magnetic directions come from the magnetic field. The magnetic equator is where the field is horizontal, not where geographic latitude is zero. Magnetic poles and the magnetic equator shift with time, so their locations need a date.
Why the others are wrong
(a) Accepts 23½° and the Canadian peninsula.
(b) Accepts the Canadian peninsula.
(c) Accepts the Canadian peninsula.
The trap
23½° is the tilt of the rotation axis — borrowed here.
Elimination technique
The 23.5-degree value refers to Earth’s rotation axis relative to the normal to its orbital plane, not the magnetic axis. Rejecting Statement 1 removes (a); the remaining choice still requires the magnetic-pole location appropriate to 2005.
Also know
Thumba near Thiruvananthapuram was selected for sounding-rocket work close to the magnetic equator. The equatorial electrojet is an electric-current belt in the upper atmosphere near that equator. Magnetic declination is the angle between magnetic north and true north; magnetic inclination is the angle the field makes with the horizontal. These are different from the tilt responsible for seasons.
🔒 Thumba (TERLS, 1963): on the magnetic equator.
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