Privileged Planet: magnetic loss and return (Introduction)

by David Turell , Wednesday, September 21, 2022, 16:38 (585 days ago) @ David Turell

At a vital time with life appearing:

https://uncommondescent.com/intelligent-design/at-big-think-how-earths-magnetic-field-b...

"To piece together the history of Earth’s magnetic field, researchers use a technique called paleomagnetism, which involves studying the alignment of metal-bearing minerals in ancient rocks. When these rocks were still molten, these minerals would have acted like tiny compass needles, aligning with the magnetic fields they encountered. As the rocks solidified, these alignments froze in place, providing geologists with a snapshot of the rocks’ magnetic environments in the distant past.

"In 2019, one such study was carried out in Sept Îles, Quebec. Here, a team of researchers examined the alignment of minerals in rocks named anorthosites, which rose to Earth’s surface during the Ediacaran Period roughly 565 million years ago. Strangely, they found that these minerals were far less strongly aligned than those found in anorthosites from other periods, suggesting that Earth’s magnetic field dipped to just around 10% of its current strength during the Ediacaran.

"If this trend had continued, the future of Earth’s capacity to sustain life may have become far less certain. Yet since this unsettling result, researchers haven’t yet determined how long it took for Earth’s magnetic field to bounce back to its present-day strength.

"A rapid resurgence: Using paleomagnetism, a new team of researchers led by Tinghong Zhou at the University of Rochester, New York, may have solved this mystery. In their study, the researchers examined the alignments of minerals within slightly newer anorthosites, taken from the Wichita Mountains in Oklahoma. These rocks solidified during the Cambrian Period, around 532 million years ago, coinciding with an evolutionary explosion of complex, multicellular organisms.

"These anorthosites only formed around 30 million years after the Quebec samples — little more than a blip on geological timescales. Yet remarkably, the mineral alignments in the rocks showed that Earth’s magnetic field had largely regained its present-day strength during that time.

"Growing an inner core: To explain this rapid renewal, Zhou’s team that the Ediacaran Period must have coincided with the formation of Earth’s inner core. Before this happened, our planet’s magnetic field may have been generated by a dynamo effect within a purely molten core, which eventually began to collapse as the Earth’s interior cooled. Yet if a solid core began to form and grow over this period, it could have provided Earth’s field with a new lease of life.

"By modelling the flow of heat from the core to the mantle, the team predicted that the solid part of the core likely began to form around 550 million years ago, expanding to half its current width by roughly 450 million years ago.

"At this point, a shift in plate tectonics on Earth’s surface would have altered the structure of the mangle surrounding the core — triggering new patterns in heat flow that persist into the present day. This suggests that Earth’s inner core likely grew in two distinct stages, with a clear boundary between its inner- and outermost parts.

"A close call: The insights gathered by Zhou’s team offer a clearer picture of the dramatic events that once unfolded deep within our planet’s interior. They also provide new hints as to how Earth narrowly avoided a Mars-like fate, just as complex, multicellular life was beginning to emerge."

Comment: a clear view of this stage of evolution of the Earth, showing again God prefers to evolve His creations. Note how closely this is timed with the start of the Cambrian explosion.