Earthquakes are a byproduct of plate tectonics, a theory in geology developed in recent years for explaining motions near the surface of the Earth. One of the benefits from plate tectonics is that Earth maintains the right levels of carbon dioxide (CO2) in the atmosphere to compensate for the Sun’s increasing luminosity. This is accomplished by what is called the carbonate-silicate cycle. CO2 is removed from the atmosphere through weathering. The weathered products are eventually drawn into the Earth’s interior via plate tectonics. Processes inside the Earth’s interior release the CO2 back into the atmosphere via volcanoes. While all aspects of this mechanism are not yet fully understood, it has been instrumental in providing a stable environment for life on the Earth for billions of years.
New research provides yet another component that appears fine-tuned for life. In a letter in the September 27, 2007 issue of Nature together with a corresponding news release from the University of Bonn, Arno Rohrbach and his colleagues have discussed another mechanism similar to the carbonate-silicate cycle. It also depends on plate tectonics but, in this case, the mechanism controls the amount of oxygen on the surface of the Earth.
Oxygen becomes bound up in various oxides which are then drawn into the Earth’s interior, where various processes result in its being incorporated into an exotic mineral called majorite. The results reported in this letter established that majorite functions as a kind of “reservoir” for oxygen, and when the majorite ascends nearer to the surface of the Earth it breaks down and releases its oxygen. Some of this oxygen also binds with hydrogen released from the interior of the Earth to form water. The authors have referred to the whole process as an “oxygen elevator.”
They go on to say that “without the ‘oxygen elevator’ in its mantle the Earth would probably be a barren planet hostile to life. According to our findings, planets below a certain size hardly have any chance of forming a stable atmosphere with a high water content.”
This research confirms the existence of one more finely tuned mechanism that depends on plate tectonics and contributes to an environment that can support life. It also gives humans one more reason to be appreciative rather than dismayed when we experience an earthquake that breaks some precious possessions beyond repair.