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Researchers: How plate tectonics, mountains and deep-sea sediments have maintained Earth’s ‘Goldilocks’ climate


In an article summarized at The Conversation, recent research affirms the suite of conditions involving plate tectonics and resultant mountain-building, coupled with erosion and volcanic activity, that has helped to maintain a habitable climate on our planet.

For hundreds of millions of years, Earth’s climate has warmed and cooled with natural fluctuations in the level of carbon dioxide (CO₂) in the atmosphere.

Our new research published in Nature, shows how tectonic plates, volcanoes, eroding mountains and seabed sediment have controlled Earth’s climate in the geological past. Harnessing these processes may play a part in maintaining the “Goldilocks” climate our planet has enjoyed.

To better understand how tectonic plates store, move and emit carbon, we built a computer model of the tectonic “carbon conveyor belt”.

The carbon conveyor belt

Tectonic processes release carbon into the atmosphere at mid-ocean ridges – where two plates are moving away from each other – allowing magma to rise to the surface and create new ocean crust.

At the same time, at ocean trenches – where two plates converge – plates are pulled down and recycled back into the deep Earth. On their way down they carry carbon back into the Earth’s interior, but also release some CO₂ via volcanic activity.

The Earth’s tectonic carbon conveyor belt shifts massive amounts of carbon between the deep Earth and the surface, from mid-ocean ridges to subduction zones, where oceanic plates carrying deep-sea sediments are recycled back into the Earth’s interior. The processes involved play a pivotal role in Earth’s climate and habitability.  Author provided image.

Our model shows that the Cretaceous hothouse climate was caused by very fast-moving tectonic plates, which dramatically increased CO₂ emissions from mid-ocean ridges.

In the transition to the Cenozoic icehouse climate tectonic plate movement slowed down and volcanic CO₂ emissions began to fall. But to our surprise, we discovered a more complex mechanism hidden in the conveyor belt system involving mountain building, continental erosion and burial of the remains of miscroscopic organisms on the seafloor.

The hidden cooling effect of slowing tectonic plates in the Cenozoic

Tectonic plates slow down due to collisions, which in turn leads to mountain building, such as the Himalayas and the Alps formed over the last 50 million years. This should have reduced volcanic CO₂ emissions but instead our carbon conveyor belt model revealed increased emissions.

We tracked their source to carbon-rich deep-sea sediments being pushed downwards to feed volcanoes, increasing CO₂ emissions and cancelling out the effect of slowing plates.

So what exactly was the mechanism responsible for the drop in atmospheric CO₂?

The answer lies in the mountains that were responsible for slowing down the plates in the first place and in carbon storage in the deep sea.

As soon as mountains form, they start being eroded. Rainwater containing CO₂ reacts with a range of mountain rocks, breaking them down. Rivers carry the dissolved minerals into the sea. Marine organisms then use the dissolved products to build their shells, which ultimately become a part of carbon-rich marine sediments.

As new mountain chains formed, more rocks were eroded, speeding up this process. Massive amounts of CO₂ were stored away, and the planet cooled, even though some of these sediments were subducted with their carbon degassing via arc volcanoes.

This recent research adds another component to effectiveness of the well-known carbonate-silicate cycle, one of many design features of our planet that set Earth apart as uniquely suitable for sustaining life.

Now what would be nice would be more research into abiotic hydrocarbon formation in the mantle, for edification against the climate madness. With raw materials CO2, H2O, silicate catalysts, and a gigantic nuclear sourced planetary furnace - the ultimate renewable energy cycle, a conveyer of that nuclear sourced energy to the surface, plus renewing the O2 supply. Put together by a designer/builder with an ancient plan for industrial civilizations that can build around it: transportation, agricultural, industrial, construction, electric power, and building heating systems. And fuel for concrete and asphalt infrastructure for convenience and comfort. A quite loving designer I would say. https://www.nytimes.com/1995/09/26/science/geochemist-says-oil-fieldsmay-be-refilled-naturally.html groovamos
Denton’s new book covers relatively briefly the fine tuning of earth’s plate tectonics system on the ability of advanced life to exist. An example:
Convection overturn occurs in the earth’s interior only because of a fortuitous combination of physical variables. If rocks were better conductors of heat, such stirring would never take place, because the necessary temperature contrasts would be subdued. If rocks didn’t expand significantly when heated there would be no density instability to drive convection. If the viscosity of Earth’s mantle rocks were much higher, the whole system would grind to a halt. Finally if the planet had a smaller inventory of radioactive elements, or if these had much shorter half-lives, the bulb in the planetary lava lamp would have burned out long ago

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