Examining Fragments of the Planet’s Oldest Ancient Rocks Offers Evidence a Way To Present Plate Tectonics

A new study analyzing fragments of the planet's oldest ancient rocks offers some of the clearest evidence yet that the Earth's crust was pushing and tugging in a way comparable to present plate tectonics at least 3.25 billion years ago.

The research also gave the first evidence of when the planet's magnetic north and south poles switched locations.

Laying the geological groundwork for life on Earth

(Photo : Rostyslav Savchyn/Unsplash)

The two findings provide insight into how such geological shifts may have resulted in a more favorable setting for the evolution of life on Earth, as per ScienceDaily.

The researchers reveal that portions of the Earth's oldest surface were changing at a pace of 6.1 centimeters per year and 0.55 degrees every million years using unique methodologies and equipment.

This pace is more than triple the rate at which the ancient crust was demonstrated to be moving in a prior investigation by the same researchers.

Plate tectonics is the most reasonable and convincing explanation for the speed and direction of this latitudinal movement.

According to AleBrenner, a Ph.D. candidate in the Graduate School of Arts and Sciences and a member of Harvard's Paleomagnetics Lab, there's a lot of work that seems to suggest that early in Earth's history plate tectonics wasn't the dominant way in which the planet's internal heat gets released as it is today through plate shifting.

This information allows us to rule out hypotheses that do not include plate tectonics with more certainty.

For example, scholars may now argue against phenomena such as real polar wander and stationary lid tectonics, both of which can cause the Earth's surface to change but are not part of current plate tectonics.

Because the newly revealed greater rate of speed contradicts the characteristics of the other two processes, the results lean more toward plate tectonic motion.

The scientists also explain what is thought to be the oldest evidence of when Earth reversed its geomagnetic fields, meaning the magnetic North and South Poles swapped positions, in the publication.

According to NASA, this sort of flip-flop is typical in Earth's geologic history, with the pole reversing 183 times in the previous 83 million years and maybe several hundred times in the last 160 million years.

The reversal reveals a lot about the magnetic field of the planet 3.2 billion years ago.

The magnetic field was likely steady and powerful enough to prohibit solar winds from degrading the atmosphere, which is one of the most important implications.

This understanding, when paired with the findings on plate tectonics, provides insights into the conditions under which the first forms of life evolved.

"It creates a picture of an early Earth that was already highly geodynamical developed," Brenner explained.

It possessed many of the same kinds of dynamic processes that result in a more stable Earth's environmental and surface conditions, making it more viable for life to emerge and develop.

The Earth's outer shell now comprises around 15 changing slabs of crust, or plates, that support the planet's continents and seas.

The earliest chunks of crust are forced into the inner mantle, never to reappear, making it difficult to determine when plate tectonics began.

Only 5% of all rocks on Earth are more than 2.5 billion years old, and none are more than 4 billion years old.

Overall, the work adds to the increasing body of evidence showing tectonic activity occurred very early in Earth's 4.5 billion-year history and that early forms of life evolved in a more temperate climate.

In 2018, project members returned to the Pilbara Craton, which runs for around 300 kilometers.

They dug through the primeval and thick slab of crust there to gather samples, which were then tested for magnetic history in Cambridge.

The Quantum Diamond Microscope was created by Harvard academics from the Departments of Earth and Planetary Sciences (EPS) and Physics.

Fu and Brenner intend to continue their research on the Pilbara Craton while also going beyond it to other ancient crusts across the world.

They are looking for ancient evidence of modern-like plate motion as well as when the Earth's magnetic poles reversed.

Read more: Tectonic Plates Are Moving Faster as Earth Ages

The theory of plate tectonics

Plate tectonics is a scientific theory that explains how significant landforms evolve as a result of underground movements on Earth, as per the National Geographic.

The hypothesis, which gained traction in the 1960s, revolutionized the earth sciences by describing a wide range of phenomena such as mountain formation events, volcanoes, and earthquakes.

Plate tectonics describes how the Earth's outermost layer, or lithosphere, which is made up of the crust and upper mantle, gets split up into enormous rocky plates.

These plates rest on top of the asthenosphere, a partly molten layer of rock.

The plates move relative to one other at varying speeds due to asthenosphere and lithosphere convection, ranging from two to fifteen centimeters (one to six inches) each year.

This tectonic plate contact is responsible for numerous geological structures, including the Himalayan mountain range in Asia, the East African Rift, and the San Andreas Fault in California, USA.

Before the 20th century, it was proposed that continents migrated throughout time. However, Alfred Wegener, a German physicist, revolutionized the scientific argument.

In 1912, Wegener published two publications on the notion of continental drift.

Despite initial dismissal, the notion gained traction in the 1950s and 1960s as fresh evidence emerged to corroborate the concept of continental drift.

Ocean bottom maps revealed a gigantic underwater mountain range that nearly ringed the whole planet.

According to an American geologist called Harry Hess, these ridges are the consequence of molten rock rising from the asthenosphere.

Related article: Scientists Discover Dinosaur-Era Sea Swallowed Up By Tectonic Plates