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It has been shown that the Earth's climate changes considerably according to geological time scales, oscillating between distinct periods of glaciation and long periods of warmer weather. The question of what has led to these periodic temperature cycles has long fascinated scientists. The researchers proposed that the tectonic activity of the plates in the tropics is actually an essential part of what drives the ice ages. To understand why, we must talk about rocks.
One of the major geological cycles impacting temperature on Earth is known as the carbon-silicate cycle. Rocks such as calcium and magnesium can sequester carbon effectively in a process called chemical weathering. The theory of the researchers is that the subduction of oceanic plates in the tropics has resulted in long sutures – areas of contact between the plates – higher up, putting for the first time what had been the bottom of the oceans in contact with the air . These areas of ancient oceanic crust are called ophiolites. This is particularly important in the tropics, particularly because, geographically, Southeast Asia contains a much larger percentage of weather-resistant rocks than other areas where this type of fault has occurred. The researchers estimate that 10 to 20% of the land area is responsible for 50 to 75% of the CO2 sequestration by bad weather.
The idea that simple chemical processes between rocks and air may represent a whole glacial period may seem fanciful, but there is a precedent for this type of interaction. The ringed iron formations that are found all over the world bear witness to a similar interaction between oxygen and iron and could have prevented the Greater Oxygen from escaping, up to the point where it was possible to escape. the amount of iron in the Earth's oceans can no longer absorb the amount of oxygen produced by photosynthetic cyanobacteria.
According to the researchers, there is a corresponding "suture" in which two tectonic plates collide, which corresponds to the three major periods in history in which we know that an ice age has occurred. These sutures were all large, 10,000 km or more, and located in the tropics, where there were the largest reserves of weather-resistant materials. These massive uprisings exposed so many new materials to the air, the amount of CO2 in the atmosphere has been falling for millions of years, leading to a new ice age.
The three ice ages in question are the last Ordovician (455 to 440 million years ago), the Permo-Carboniferous (335 to 280 million years ago) and the Cenozoic (there are has 35 million years – today). There is, however, no trace of the ice age in the historical record corresponding to a major non-tropical suture. This is the uplift of rocks that could sequester carbon, especially associated with glacial periods.
The authors write:
While recognizing that volcanic degassing has had to change over time and that burial of organic carbon has also had an impact on the climate in the long term, our analysis suggests that weather resistance in the world has provided control of first order of the state of the climate of the Earth. In particular, continental arc collisions in the tropics, such as today's Indonesian orogenic system, are ephemeral on geologic time scales and when they drift out of the tropics or into the tropics. As the exhumation ceases and the topography is eroded, the Earth regains a non-glacial state. Thus, our model takes into account both the initiation and the end of the glacial ages.
It has even been proposed to grind large quantities of ophiolites and use their ability to chemically sequester carbon dioxide to compensate for human CO.2 shows. Unfortunately, the time scales on which this process usually works make this concept highly improbable. If plate tectonics produced significant cooling trends on Earth, the process was still taking millions of years. Humanity just does not have that kind of time.
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