Gravity is still shaping Earth's surface from deep within, new study finds

Gravity is still shaping Earth’s surface from deep within, new study finds

Like all planets, the Earth is the product of gravity. Gradually, the growing mass of dust and rock attracted enough material to become a puffy mineral sphere we now call home.

Even today, gravity continues to shape our planet from the inside, in ways that are much more delicate than we imagine. A new study highlights the subtle gravitational effects deep structures can have on the rise and fall of the crust above.

The researchers behind the study liken it to the mass of ice attached to an iceberg underwater, which isn’t immediately visible but still has an important role to play in structure and movement. which occur above.

These deep gravitational pulls and pushes are capable of creating dramatic movements along faults in the earth’s crust, collapsing mountain ranges and exposing rocks that once lay up to 24 kilometers or 15 miles below the surface. , producing structures known as metamorphic core complexes.

While many studies have already attempted to explain the precise mechanisms of formation of metamorphic complex nuclei, the conditions of their evolution remain a mystery. Weighing in on the decades-long debate over the origins and mechanics of these complexes, researchers have identified the key geological processes behind their formation.

The team studied metamorphic core complexes around Phoenix and Las Vegas in the United States, confirming that they appear to be remnants of previously collapsed mountain belts.

Using computer modeling to plot how the landscape had most likely shifted over time, the researchers found that the primary driver of formation of the metamorphic core complex appears to be thickening and then weakening of their crustal roots.

Crustal roots form where the lighter crust thickens beneath a mountain range, penetrating and replacing the heavier mantle. Weakened by processes such as heat, fluid movement and rock melting, the researchers explain, these thickened mountain soles can collapse, distorting the contrasting layers of crust below.

This exposes the surface of metamorphic core complexes in an “ascending dome-shaped chain” and traces of their turbulent formation can be seen in deformed rocks known as mylonites.

According to the researcher’s models, this extensional collapse is entirely caused by gravity pulling on different densities of material in the overlying crust and its boundary with the mantle.

Computer models of gravitational forces
Computer modeling was used to identify the gravitational forces at work. (Bahadori et al., Nature Communication, 2022)

The research builds on two previous, related studies by the same team of researchers: In a 2022 study, they modeled the same region of the southwestern United States, showing what it might have looked like before, during and after metamorphic base complexes, linking tectonic movement with climatic changes.

Prior to that, a 2021 study by the same group showed how deep Earth forces combine with climate to influence the landscape and impact the diversification of mammals and the dispersal of species found in the fossil record.

The new research could change the way we understand Earth’s history and predict how its geology may continue to evolve in the future as gravity tears and pushes its crust away.

Additionally, the researchers believe their modeling approach could help geologists understand other mountainous regions around the world where crustal roots have thickened and partially collapsed.

According to the researchers, the results of the study “probably explain many exposures of ancient gneissic domes around the world, where the fragile cover has likely been removed by erosion, exposing the uplifted metamorphic dome core.”

The research has been published in Nature Communication.

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