Currently, scientists at MIT, the University of California at Santa Barbara and the University of California at Berkeley have identified a likely initiator for these glacial periods.
In a study published in Science the team reports that each of the last three large glacial periods was preceded by tropical "collisions of the arccontinent" ̵
Scientists argue that the warmth and humidity of the tropics are likely to cause a chemical reaction between the rocks and the atmosphere. In particular, calcium and magnesium rocks reacted with atmospheric carbon dioxide, extracting gas from the atmosphere and constantly sequestering it in the form of carbonates, such as limestone. Over time, researchers say, this weathering process takes place through millions of square kilometers, can extract enough carbon dioxide from the atmosphere to cool the temperature all over the world and, eventually, depart from the glacial period.
"We believe that collisions at the lower latitudes are the basis for global cooling," says Oliver. Yagutz, associate professor of the Department of the Earth, atmospheric and planetary sciences MIT. "It can happen for about 1-5 million square kilometers, which sounds like a lot. But in fact, it's a very thin band of the Earth that sits in the right place that can change the global climate."
Jagoutz – sponsored by Francis McDonald and Lorraine Lisietsky from UC Santa Barbara, and Nicholas Swanson-Housell and Yuem Park UC Berkeley.
When an oceanic stove pushes onto a continental plate, a collision usually creates a mountain range of the newly exhibited rock. The fault zone encountered by ocean and continental plates is called a "seam". Today, some mountain ranges, such as the Himalayas, contain seams that migrated from their initial points of collision, since the continents have shifted for millennia
In 2016, Yagutz and his colleagues tracked the movements of two joints that today form the Himalayas. They found that both seams originated from the same tectonic migration. Eighty million years ago, as a supercontinent, known as Gondwana, moved north, part of the land was crushed against Eurasia by exposing a long line of oceanic rocks and creating the first seam; 50 million years ago, another collision between supercontinents created a second seam
The team found that both collisions occurred in tropical zones near the equator, and both preceded the global atmospheric cooling of several million years, which is almost instantaneous on the geological time scale. After studying the pace at which ocean-shaped oaks were exposed, they were also known as oily peal, they could react with carbon dioxide in the tropics, the researchers concluded that, given their location and size, both seams could indeed sequester enough carbon dioxide to cool the atmosphere and
Interestingly, they discovered that this process is likely to be responsible for terminating both glacial periods. For millions of years, the oceanic rock that was available to respond to the atmosphere, later eroded, replaced by a new rock, which was much less carbon dioxide.
"We have shown that this process can begin and finish glaciation," says Yagut. . "Then we asked how often it works. If our hypothesis is correct, we must find that there are plenty of seams in the tropics for each time it is cooled."
Disclosures of Earth's Seams
The researchers looked at whether glaciers further on Earth's history were associated with similar clashes in the tropics. They conducted an extensive literary search to gather the location of all major seams on Earth today, and then used a computer simulation of tectonics of plates to restore the movement of these sutures, as well as continental and oceanic planes of the Earth in time. Thus, they were able to determine precisely where and when each seam was originally formed and how long each stitch stretched out.
They identified three periods during the last 540 million years, in which large seams, about 10,000 kilometers long, formed in the tropics. Each of these periods coincided with each of the three main, well-known glacial periods, in the late Ordovician (455-440 million years ago), percarbon (335-280 million years ago) and Cenozoic (35 million years). to this day). It is important that they discovered that there were no glacial periods or glaciations at periods when the main zone zones were formed outside the tropics.
"We found that every time there was a peak in the seam area in the tropics, there was glaciation," says Yagut. "Thus, every time you get, say, 10,000 kilometers of seams in the tropics, you get a glacial period. "Responsible for the current period of the glacial period of the Earth and the appearance of large ice sheets at the poles
This tropical zone includes some of the largest ophiolite bodies in the world and is currently one of the most efficient regions on Earth for carbon sequestration and absorption. dioxide. Since global No temperature is raised as a result of carbon dioxide produced by humans, some scientists have proposed grinding large quantities of oily peptides and spreading minerals around the equatorial belt to accelerate this natural cooling process.
says that the act of shredding and transporting these materials may lead to additional, unintentional carbon emissions, and it is unclear whether such measures can have a significant impact throughout our lives.
"It is a challenge for this process to work on human timeframes," says Yagutz. "Earth does it in a slow, geological process that has nothing to do with what we do today with the Earth, and this will not harm us, and will not save us."
Ancient tectonic activity was a trigger for glacial periods, the study says
"Collisions of arch continents in the tropics have established the state of the Earth's climate" Science (2019). science.sciencemag.org/lookup/… 1126 / science.aav5300