1929: Geomagnetic reversals - The book of science

Geomagnetic reversals
Sea-floor record
Disorder
Commentary

Geomagnetic reversals

Compass needles point north
although they wouldn’t have always.
Fixed in molten rock, the magnetic orientations
of basalts was confusing; people had found rocks
with the opposite polarity; so scientists supposed
that the magnetic field of the earth had once reversed.
Motonori Matuyama gathered basalt samples
in Manchuria and Japan and was able to show
a correlation between the magnetic orientations
and the position of the rocks in the strata.
It turns out the magnetic polarity has flipped
many times in the distant, distant past.

Sea-floor record

Symmetrical parallel stripes on each side
of the mid-ocean ridges
oriented magnetically north, then south
show that the sea floor has spread
and that the polarity of the earth’s magnetic field
has reversed at random many times
written in the sea floor as on a scroll.

Disorder

The earth’s magnetic field
is not as simple
as a bar magnet’s.
During a reversal, temporary
knots of alignments turn
about at different times.
Like a creative
process, characterized by
disorder and confusion,
one can not predict
the progress or conclusion
of the transforming process
only after which
it might seem that
reason has prevailed.

Motonori Matuyama’s proof generated little interest at the time; however, it became more significant in the late fifties when studies of continental drift and sea-floor spreading required an understanding of geomagnetic reversals. Today, the most recent reversal is named after him.