How Earth's Hidden Magma Ocean Formed

Artist’s impression of the enormous collision that formed the moon. — Prior research suggested that after a giant rock slammed into Earth to form the moon some 4.5 billion years ago, a magma ocean covered most of Earth's surface.

(Image credit: NASA/JPL-Caltech)

The rotation of the newborn Earth may have helped to control the evolution of a giant magma ocean sitting on top of its core, researchers say.

Knowing how Earth's magma oceans evolved over time could shed light on when the plate tectonics— the shifting of the rocky slabs that make up the planet and underlie earthquakes and volcanoes — began, scientists added.

Previous calculations suggested that Earth possessed one or more giant oceans of magma, or molten rock. For instance, after a Mars-size rock slammed into Earth about 4.5 billion years ago to create the moon, prior research suggested a magma ocean about 620 miles (1,000 kilometers) deep covered most of Earth's surface, according to prior research. [In Photos: Watery Ocean Hidden Beneath Earth's Surface]

Latest Videos From

Watch full video here:

Understanding more about how Earth's molten rock crystallized over time could yield insights on when the planet first developed a magnetic field, which could have shielded the planet from deadly solar radiation, setting the stage for the origin of life on Earth. In addition, "the crystallization of the magma ocean set the initial conditions for plate tectonics," said study lead author Christian Maas, a geophysicist at the University of Münster in Germany.

When the model did not rotate, heavier silicate crystals sank deeper into the magma ocean, while lighter crystals settled on top of the heavier crystals, as one might expect. However, when the model did spin, the rotational force on the crystals made them behave differently at the equator than at the poles. At the poles, the heavier crystals sank to the bottom, while the lighter crystals settled on top of them. But at the equator, the heavier crystals accumulated at mid-depths, while the lighter crystals sank to the bottom.

Maas noted that this research modeled the poles and equator separately from each other. "The next step is therefore to simulate the whole magma ocean, including the poles, the equator and the region between the poles and the equator," Maas said. "Even with the newest computer equipment, simulations will take months." Eventually, such research could help shed light on how the magma ocean crystallized and help trigger plate tectonics.

TOPICS

Charles Q. Choi is a contributing writer for Live Science and Space.com. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.