Page 8 - SEG - First issue

Academic Articles
IV- Geophysics

- Magnetic Method -

The magnetic method of surveying subsurface

rocks to know the lithology of the rocks is one of
the geophysical methods to gather information
from the earth and in our case we are looking at

the magnetic susceptibility as our data from the
rocks magnetic susceptibility which is an induced
property by earth's magnetic field which in turn
comes from the movement of lava around the hard
inner core of the earth which creates the electricity

and give this magnetic field that surrounds the
earth also other elements play a role in creating
earth's magnetic field like external magnetization

by the sun and it's reaction to the ozone layer and
spatial surface structures that get magnetized and
then give a magnetic field.
rocks which are susceptible to a magnetic field are
hardly sedimentary rocks with igneous and

metamorphic being the most concentrated on
when using the magnetic method. Another big
factor in the magnetization of rocks is curie

temperature which is the temperature which
above it the rock would lose it's magnetic property
and below it the rock gains the magnetic property
as it solidifies and cool down.

Magnetic surveys are made with several instruments, how ever the proton-

precession magnetometer gives more accurate information than the other
instruments and here is how it works .

The proton magnetometer measures a radio-frequency voltage induced in a coil
by the reorientation (precession) of magnetically polarized protons in a container

of ordinary water.

Magnetic surveys are mostly done by air through planes scanning the earth for
the magnetic information how ever when there is an anomaly in the ground that

the exploration team or the scientists want to study carefully they scan that area

again but on foot and on a smaller scale than the previous one . a survey doesn't
usually take place when there are large magnetic fluctuations (Magnetic Storms )

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