BREAKING NEWS: A New Powerful Study Affirms Battros 2012 Equation

When Earth overheats, it finds its way to maintain its ambient temperature. In very much the same way humans sweat through our pores to cool off, in like manner, Earth sweats by producing increased mantle plume activity.

New research released this week confirms increased heat from Earth’s core strengthens the flow viscous material (liquefied rock) upward through the mantle having an effect on tectonic plates, including seamounts which in-turn heats the oceans.

For decades, scientists have theorized that the movement of Earth’s tectonic plates is driven largely by negative buoyancy created as they cool. New research, however, shows plate dynamics are driven significantly by the additional force of heat drawn from the Earth’s core.

The new findings also challenge the theory that underwater mountain ranges known as mid-ocean ridges are passive boundaries between moving plates. The findings show the East Pacific Rise, the Earth’s dominant mid-ocean ridge, is dynamic as heat is transferred.

David B. Rowley, professor of geophysical sciences at the University of Chicago, and fellow researchers came to the conclusions by combining observations of the East Pacific Rise with insights from modeling of the mantle flow there. The findings were published Dec. 23 in Science Advances.

“We see strong support for significant deep mantle contributions of heat-to-plate dynamics in the Pacific hemisphere,” said Rowley, lead author of the paper. “Heat from the base of the mantle contributes significantly to the strength of the flow of heat in the mantle and to the resultant plate tectonics.”

The researchers estimate up to approximately 50 percent of plate dynamics are driven by heat from the Earth’s core and as much as 20 terawatts of heat flow between the core and the mantle.

Unlike most other mid-ocean ridges, the East Pacific Rise as a whole has not moved east-west for 50 to 80 million years, even as parts of it have been spreading asymmetrically. These dynamics cannot be explained solely by the subduction of a process whereby one plate moves under another or sinks. Researchers in the new findings attribute the phenomena to buoyancy created by heat arising from deep in the Earth’s interior.

“The East Pacific Rise is stable because the flow arising from the deep mantle has captured it,” Rowley said. “This stability is directly linked to and controlled by mantle upwelling,” or the release of heat from Earth’s core through the mantle to the surface.

The Mid-Atlantic Ridge, particularly in the South Atlantic, also may have direct coupling with deep mantle flow, he added.

“The consequences of this research are very important for all scientists working on the dynamics of the Earth, including plate tectonics, seismic activity and volcanism,” said Jean Braun of the German Research Centre for Geosciences, who was not involved in the research.

The forces at work

Convection, or the flow of mantle material transporting heat, drives plate tectonics. As envisioned in the current research, heating at the base of the mantle reduces the density of the material, giving it buoyancy and causing it to rise through the mantle and couple with the overlying plates adjacent to the East Pacific Rise. The deep mantle-derived buoyancy, together with plate cooling at the surface, creates negative buoyancy that together explain the observations along the East Pacific Rise and surrounding Pacific subduction zones.

A debate about the origin of the driving forces of plate tectonics dates back to the early 1970s. Scientists have asked: Does the buoyancy that drives plates primarily derive from plate cooling at the surface, analogous with cooling and overturning of lakes in the winter? Or, is there also a source of positive buoyancy arising from heat at the base of the mantle associated with heat extracted from the core and, if so, how much does it contribute to plate motions? The latter theory is analogous to cooking oatmeal: Heat at the bottom causes the oatmeal to rise, and heat loss along the top surface cools the oatmeal, causing it to sink.

Until now, most assessments have favored the first scenario, with little or no contribution from buoyancy arising from heat at the base. The new findings suggest that the second scenario is required to account for the observations, and that there is an approximately equal contribution from both sources of the buoyancy driving the plates, at least in the Pacific basin.

“Based on our models of mantle convection, the mantle may be removing as much as half of Earth’s total convective heat budget from the core,” Rowley said.

Much work has been performed over the past four decades to represent mantle convection by computer simulation. Now the models will have to be revised to account for mantle upwelling, according to the researchers.

“The implication of our work is that textbooks will need to be rewritten,” Rowley said.

The research could have broader implications for understanding the formation of the Earth, Braun said. “It has important consequences for the thermal budget of the Earth and the so-called ‘secular cooling’ of the core. If heat coming from the core is more important than we thought, this implies that the total heat originally stored in the core is much larger than we thought.

“Also, the magnetic field of the Earth is generated by flow in the liquid core, so the findings of Rowley and co-authors are likely to have implications for our understanding of the existence, character and amplitude of the Earth’s magnetic field and its evolution through geological time,” Braun added.

Rupture in Lithosphere Driving Undersea Volcanism

Scientists analyzing a volcanic eruption at a mid – ocean ridge under the Pacific have come up with a somewhat contrarian explanation for what initiated it. Many scientists say undersea volcanism is triggered mainly by upwelling magma that reaches a critical pressure in the lithosphere and forces its way up. The new study says the dominant force, at least in this case, was the seafloor itself – basically that it ripped itself open, allowing magma to spill out. The eruption took place on the East Pacific Rise, some 700 miles off Mexico.

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“Mid – ocean ridges are commonly viewed as seafloor volcanoes, operating like volcanoes on land,” said the study’s lead author, Yen Joe Tan, a graduate student at Columbia University’s Lamont – Doherty Earth Observatory. “We’re saying they should actually be viewed as tears in the crust, where magma oozes out.” The study appears in the journal Nature this week.

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The authors of the new paper took another look after a 2015 eruption at an unconnected study site, at Axial Seamount, off the coast of Oregon. Unlike the earlier East Pacific Rise eruption, this one was studied in real time with an assortment of instruments. Among the data produced were recordings of violent popping noises that appeared related to the emergence of lava on the seafloor – possibly the result of exploding gas bubbles, or implosions of hardening lava.

In light of the Axial Seamount observations, the researchers reviewed the 2005 – 2006 data from the East Pacific Rise, and came up with a newly sharpened picture. Their reanalysis suggested that most of the eruption took place rapidly, not over months. Other researchers had already identified a series of conventional earthquakes of about magnitude 2 on Jan. 22, 2006, of the kind usually associated with the rupture of a rock boundary, along a 35 – kilometer – long segment of the ridge. About 15 minutes later, the seismometers started picking up clusters of lower – frequency earthquakes, of a type usually associated with rising magma. Another hour or two on, popping sounds like those heard at Axial Seamount appeared, in four separate areas along the segment, each in an area about 5 kilometers long.

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“It’s been a kind of chicken – and – egg question,” said coauthor Maya Tolstoy, a marine geophysicist at Lamont – Doherty. “You have these two different forces [magma vs. tectonics] that could play a role, and it’s hard to tell which triggers the eruption. Here, we can make the argument for one dominating, because we see this series of events, and then multiple magma chambers erupting at the same time.”

The authors say that according to their observations, about 85 percent of the lava emerged within two days, with remnants dribbling out over the course of a week. The eruptions produced some 22 million cubic meters of seafloor – about enough to cover 13 football fields 1,000 feet deep.

Cynthia Ebinger, a professor at the University of Rochester who studies eruptions at spreading sites both on land and under the ocean, said in an email that very few seafloor eruptions have been so directly observed. The study “adds a new factor to consider,” she said. “It shows that tectonic stresses can trigger large – volume intrusions and eruptions” to create new seafloor.

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Michael Perfit, a professor at the University of Florida who also studies undersea eruptions, said the study “tells a remarkable story.” But, he said, the authors may have overstated the relative role of tectonic stress versus magma pressure. “I think it’s really got to be both,” he said. He cited a 2014 geochemical study he coauthored suggesting that the magma was replenished with new material from below about 6 weeks before the eruption. This suggests pressure could have played a more substantial role, he said.

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