4. Introduction to
Paleomagnetism
Paleomagnetism is the study of
magnetism in rocks to record
the history of the magnetic field.
Magnetism in rocks is caused
by the earth's magnetic field
during their formation.
Paleomagnetism gives proof of
Earth’s evolution that takes place
in the past upto 200mya, for
further collection of
paleomagnetic data, scientist
used magnetite bearing samples
to reconstruct paleomagnetism.
5. The shifting locations of the
geomagnetic poles are
recorded in rocks that form
when molten material called
magma wells up through
Earth's crust and pours out as
lava. As lava cools and
becomes solid rock, strongly
magnetic particles within the
rock become magnetized by
Earth's magnetic field.
6. Polar Wandering
Polar wander is the motion of a pole
in relation to some reference frame. It
can be used, for example, to measure
the degree to which Earth's magnetic
poles have been observed to move
relative to the Earth's rotation axis.
8. We have seen that rock samples containing magnetic
minerals (commonly magnetite and haematite) provide
information (direction and inclination) on where they were
formed relative to the north magnetic pole.
Turning this around – if we collect recent volcanic rocks from
different places around the world, measurement of their
magnetic direction and inclination will converge on the
present magnetic north pole.
If we measure their magnetic inclination and direction, we
might expect that rocks of the same age on different
continents would give identical polar positions, which should
correspond with the present polar position.
9. Rocks of different ages give different polar
positions.
Rocks of the same age but on different
continents give same polar positions.
The older the rock the further the calculated
polar position is from the present position.
10. Reversal Of Earth’s magnetic Field
While that may sound like a big deal, pole
reversals are common in Earth's geologic
history. Paleomagnetic records tell us
Earth's magnetic poles have reversed 183
times in the last 83 million years, and at
least several hundred times in the past
160 million years.
11.
12. Consequences of Reversal of Earth’s Magnetic
field:
As Earth's magnetic shield fails, so do its satellites, as they works
on signals and disturbance to signals leads to their failure and
eventually they falls on Earth due to Gravitational pull.
Cosmic rays start to bombard every human on Earth.
It leads to failure of communications and power grids.
Earth can lose its atmosphere.
It also affect animal species, they lose there ways of migration as
studies shows that they uses Earth’s magnetic field for exploration
purposes.
13. Earth's polarity is not a constant. Unlike a classic bar magnet, or the
decorative magnets in our refrigerator, the matter governing Earth's
magnetic field moves around is different. Geophysicists are pretty
sure that the reason Earth has a magnetic field is because its solid
iron core is surrounded by a fluid ocean of hot, liquid metal. This
process can also be modeled with supercomputers. Ours is, without
hyperbole, a dynamic planet. The flow of liquid iron in Earth's core
creates electric currents, which in turn create the magnetic field. So
while parts of Earth's outer core are too deep for scientists to
measure directly, we can infer movement in the core by observing
changes in the magnetic field. The magnetic north pole has been
creeping northward – by more than 600 miles (1,100 km) – since the
early 19th century, when explorers first located it precisely. It is
moving faster now, actually, as scientists estimate the pole is
migrating northward about 40 miles per year, as opposed to about 10
miles per year in the early 20th century.
