Approximately 591 million years ago, the Earth's magnetic field weakened significantly. Surprisingly, a recent study suggests that this event may have actually contributed to the development of complex life forms on our planet.
According to John Tarduno, a geophysics professor at the University of Rochester and the study's lead author, the Earth's magnetic field typically acts as a protective shield. Without this shield, the solar wind - a flow of energetic particles from the Sun - could have stripped away water from Earth during its early history.
"During the Ediacaran period, there was a significant phase of evolution occurring deep within the Earth. The processes responsible for generating the magnetic field became highly inefficient after billions of years, resulting in a near-collapse of the field," he clarified.
The findings, which have been published in the journal Communications Earth & Environment, indicate that the Earth's magnetic field, generated by the movement of molten iron in the outer core, was considerably weaker than its current strength for a minimum of 26 million years. This discovery of the prolonged weakness of the magnetic field also contributes to solving a long-standing geological puzzle regarding the formation of the Earth's solid inner core.
This time period aligns with the Ediacaran Period, a time when the first complex organisms emerged on the ocean floor due to increased oxygenation of the atmosphere and oceans.
These strange animals hardly resemble anything we see today, including squash propellers, tubes, donuts, and discs such as Dickinsonia, which reaches 4.6 feet (1.4 meters) in size, and the slug-like Kimberella.
Before this time, life was largely single-celled and microscopic. The researchers believe that the weak magnetic field may have led to an increase in oxygen in the atmosphere, allowing the evolution of early complex life.
Detection of impending collapse of the magnetic field
It is known that the strength of the Earth's magnetic field fluctuates over time, and the crystals preserved in rocks contain small magnetic particles trapped in a record of the strength of the Earth's magnetic field.
The first evidence that the Earth's magnetic field weakened significantly during that era was revealed by a study conducted in 2019, on 565 million-year-old rocks in Quebec, which indicated that the magnetic field was ten times weaker than it is today, at that point.
The most recent research has gathered additional geological proof indicating a significant weakening of the magnetic field. Analysis of a 591 million-year-old rock from a location in southern Brazil revealed that the magnetic field was 30 times weaker than its current strength.
The team discovered that the Earth's magnetic field was much stronger over two billion years ago when they examined rocks from South Africa. During that time, the innermost part of the Earth was liquid, not solid, which impacted the generation of the magnetic field.
As time passed, this process became less effective, according to Tarduno. By the Ediacaran era, the magnetic field was weakening and on the brink of collapsing. Luckily, the inner core cooled down, leading to the strengthening of the magnetic field.
The emergence of the oldest complex life forms floating along the sea floor in this era is linked to rising oxygen levels. Tarduno noted that some animals can survive at low levels of oxygen, such as sponges and microscopic animals, but larger animals with more complex bodies that move need more oxygen.
Study co-author Shuhai Xiao, a professor of geobiology at Virginia Tech, explained that traditionally, the rise in oxygen during this phase has been attributed to photosynthetic organisms such as cyanobacteria, which produced oxygen, allowing it to accumulate in the water steadily over time.
However, the new research has come up with an alternative or complementary hypothesis that involves increased hydrogen loss of spacing when the Earth's magnetic field is weak.
“The magnetosphere protects the Earth from the solar wind, thus keeping the atmosphere attached to the Earth. Therefore, a weaker magnetosphere means the loss of lighter gases such as hydrogen from the Earth’s atmosphere.”
Tarduno pointed out that it is possible for multiple operations to occur simultaneously.
He said, "We do not dispute that one or more of these processes were occurring simultaneously. But the weak field may have allowed oxygen to exceed the threshold, which helped the development of animal radiation."
Peter Driscoll, a scientist at the Earth and Planetary Laboratory at the Carnegie Institution for Science in Washington, DC, America, who was not involved in the study, said that he agreed with the results of the study regarding the weakness of the Earth’s magnetic field, but the claim that the weak magnetic field may affect oxygen in the atmosphere and biological evolution, was... It is difficult to evaluate.
He noted, "It is difficult for me to evaluate the validity of this claim because the impact that planetary magnetic fields may have on climate is not well understood."
Tarduno explained that their hypothesis was "solid," but proving causality could take decades of difficult work given how little is known about animals that lived in that era.
The mystery of the Earth's core
Through geological analysis, significant information about the Earth's innermost core has been uncovered.
It is believed that the Earth's inner core solidified and iron first crystallized in the planet's center between 500 million and 2.5 billion years ago.
Studies on the Earth's magnetic field strength suggest that the inner core is relatively young, solidifying after 565 million years ago, which enabled the Earth's magnetic shield to recover.
"The observations seem to support the claim that the inner core first formed shortly after this time, pushing the geodynamo (the mechanism that creates the magnetic field) from a weak, unstable state to a strong, stable dipole field," Driscoll said.
The restoration of field strength after the Ediacaran, as the inner core grew, may have been important in preventing the water-rich Earth from drying out, Tarduno said.
As for the exotic animals of the Ediacaran, they were all gone by the following Cambrian, when the diversity of life exploded and the branches of the tree of life familiar today formed in a relatively short time.
You must be logged in to post a comment.