In 1860 the magnetic bearing of a line was n69 270 w with a magnetic declination of 5° 120' e. compute the magnetic bearing of this line today if the magnetic declination is now 7o 360' e. what is the astronomic bearing of this line?

a) N60°30'W

b) astronomic bearing = 299°30'

Explanation:

Given:

Magnetic bearing = N69°270'W

Magnetic declination = 5° 120' E

Now,

True bearing =  Magnetic bearing - Magnetic declination

or

True bearing = N69°270'W - 5° 120' E = 64°150'

also,

The current magnetic declination is 7°360'E

therefore,

The present magnetic bearing = 64°150' - (7°360'E - 5° 120' E )

or

The present magnetic bearing = 64°150' - 2°240' = N60°30'W

Now,

the astronomic bearing of this line = 360° - 60°30' = 299°30'

the correct answers are:

a - pacific plate;

it is the biggest oceanic tectonic plate. surrounded on all sides by continental tectonic plates, it is submerging and gradually becoming smaller and smaller.

b - north american plate;

huge continental plate, occupying big portion of the northern hemisphere.

c -eurasian plate;

alongside the north american plate, it is one of the two dominant continental plates in the northern hemisphere.

d - indian plate;

a small continental plate, that has been part of gondwanaland initially, but after the break up of it, moved towards northeast and pushed into the eurasian plate that was once part of laurasia.