Turns out, Earth's
ancient magnetic field was significantly different than the present day field,
originating from several poles rather than the familiar two.
Scientists are able
to reconstruct the planet's magnetic record through analysis of ancient rocks
that still bear a signature of the magnetic polarity of the era in which they
were formed. This record suggests that the field has been active and dipolar,
having two poles, through much of our planet's history.
The geological record
also doesn't show much evidence for major changes in the intensity of the
ancient magnetic field over the past 4 billion years. A critical exception is
in the Neoproterozoic Era, 0.5 to 1 billion years ago, where gaps in the
intensity record and anomalous directions exist. Could this exception be
explained by a major event like the solidification of the planet's inner core?
In order to address
this question, Carnegie's Peter Driscoll modeled the planet's thermal history
going back 4.5 billion years. His models indicate that the inner core should
have begun to solidify around 650 million years ago. Using further 3-D dynamo
simulations, which model the generation of magnetic field by turbulent fluid
motions, Driscoll looked more carefully at the expected changes in the magnetic
field over this period.
His results showed
that around 1 billion years ago, Earth could have transitioned from a
modern-looking field, having a "strong" magnetic field with two
opposite poles in the north and south of the planet, to having a
"weak" magnetic field that fluctuated wildly in terms of intensity
and direction and originated from several poles. Then, shortly after the
predicted timing of the core solidification event, Driscoll's dynamo simulations
predict that Earth's
magnetic field transitioned back to a "strong," two-pole one.
"These findings
could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic
record around 600 to 700 million years ago," Driscoll noted. "And
there are widespread implications for such dramatic field changes."
It is published in
Geophysical Research Letters.
Representative
Image
Source:
ANI
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
ConversionConversion EmoticonEmoticon