New research on the chemistry of oxygen and iron under the extreme conditions found in the interior of the Earth could explain a long-standing seismic mystery called ultra-low speed zones. Published in Nature the findings could have far-reaching implications for our understanding of Earth's geological history, including life-altering events such as the Great Oxygenation Event, which occurred 2,400 million years ago.
Sitting at the boundary between the lower mantle and the core, 1,800 miles below the surface of the Earth, the ultralow-speed zones (UVZ) are known to scientists because of their unusual seismic signatures. Although this region is too deep for researchers to see directly, the instruments that can measure the propagation of seismic waves caused by earthquakes allow them to visualize changes in the Earth's interior structure; similar to how ultrasound measurements allow medical professionals to look inside our bodies.
These seismic measurements allowed scientists to visualize these zones of ultra-low speed in some regions along the boundary between the mantle and the core, observing the deceleration of the seismic waves that pbad through them. But knowing that the UVZ exist did not explain what caused them.
However, recent findings on the chemistry of iron and oxygen under deep Earth conditions provide an answer to this long-standing mystery.
It turns out that the water contained some minerals being dragged to Earth because the tectonic activity of the plates could, under extreme pressures and temperatures, separate, releasing hydrogen and allowing the residual oxygen to combine with the metallic iron of the core to create a new high-pressure mineral, iron peroxide. 19659003] Directed by Ho-kwang "Dave" Mao of Carnegie, the research team believes that up to 300 million tons of water could be transported into the Earth's interior each year and generate deep and mbadive deposits of iron dioxide, which it could be the source of ultralow speed zones that slow seismic waves at the boundary between the core and the mantle.
To test this idea, the team used sophisticated tools at the Argonne National Laboratory to examine the propagation of sonic waves through iron peroxide samples that were created under conditions of pressure and temperature that mimicked the deep Earth using a diamond anvil cell heated by laser. They discovered that a mixture of normal mantle rock with 40 to 50 percent iron peroxide had the same seismic signature as the ultra-low speed enigmatic zones.
For the research team, one of the most exciting aspects of this finding is the potential for an oxygen reserve inside the planet, which if released periodically to the surface of the Earth could significantly alter the primitive atmosphere of the planet. Earth, which could explain the dramatic increase in atmospheric oxygen that occurred about 2,400 million years ago according to the geological record.
the existence of a giant internal oxygen reservoir has many far-reaching implications, "explained Mao." Now we should reconsider the consequences of sporadic oxygen bursts and their correlations with other important events in Earth's history, such as the formation of banded iron, snowball, mbad extinctions, flood basalts and supercontinent ruptures. "
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