continents

The oldest rocks on Earth are in Australia and force us to rethink how the continents were formed

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The Earth works with the mechanics of plate tectonics, that is, tectonic plates move, collide and sink under each other. The question on the table of science is when it started to work like this and the answer is complicated, simply because no rock older than 4,030 million years is preserved that allows us to reconstruct that period (spoiler: It is the Acasta gneiss and is in Canada). The only clue we have are zircons, crystals so resistant that they can almost withstand anything: they survive even when the rock that houses them disappears, so they function as a kind of time capsule. The oldest in the world They are in the hills of Jack Hillsin Western Australia and are up to 4.4 billion years old. The discovery. An international research team led by John W. Valley of the University of Wisconsin-Madison has analyzed the chemical composition of these Australian zircons and compared it with other zircons of approximately the same age found in Barberton, South Africa. What they found was surprising: while the South Africans point to a still and immobile Earth’s crust, the Australians indicate that in that place, one layer was sinking on top of another (subduction). The conclusion they reached is that 4.4 billion years ago different parts of the Earth operated with different tectonic mechanisms at the same time: in some places there was something similar to silver tectonics and in others, the crust remained stagnant, as if it were a rigid lid. Why is it important. Until now, the official history of Earth’s geology tells that the planet went from having a stationary crust to having plate tectonics. around 3.8 billion years and that the change was more or less global and simultaneous. Well nothis study dismantles it: subduction was already happening in some parts 600 million years earlier, which means that the continents began to form much earlier than previously thought. And there were earthquakes back then. This is also important for understanding the origin of life. Subduction produces granite and stable continental crust, which creates land, nourishes the oceans with minerals, and creates the environments where, according to the oldest records available, life began to develop 3,700 – 4,100 million years ago. If subduction dates back to before, those favorable conditions for life were also there before. Context. This debate is not new and in fact, neither is the conclusion. There are studies that hold that plate tectonics began in the early Hadean, others that before the plates began to move, the Earth’s crust was a rigid, immobile layer, like a lid, and the heat from within was released through columns of molten rock rising from the mantle, not through the movement and collision of plates. And be careful, because in both cases they used those same Jack Hills zircons to defend opposing positions, which gives an idea of ​​how difficult it is to interpret them. In fact, already there are previous studies that use Barberton zircons to identify a tectonic regime change around 3.8 billion years ago. What this new work does is add a nuance in the form of complexity: the change was present in Barberton, but in Australia in Jack Hills the story was different and older. How they have done it. With a technique called secondary ion mass spectrometry (SIMS), which makes it possible to measure with high precision some chemical elements present in zircon (scandium, ytterbium, niobium and uranium) because their proportions vary depending on the type of geological environment in which the mineral was formed. A zircon formed in a subduction zone has very different proportions than one formed in a rigid cap zone. In addition, they analyzed the age of the zircons and their hafnium and oxygen isotopes, which indicate both the origin of the mantle or whether water was involved in the process. The complete photo with these four data allows us to reconstruct the geological environment. Yes, but. The big Achilles’ heel of the study is that these zircons are loose grains carried by erosion, not samples of rock in their original place. That is, they could travel thousands of kilometers from their origin. In short: it is not known where they come from. The second major problem is that the method used to identify tectonic environments is calibrated with modern rocksbecause there are no Hadean rocks. This implies assuming that the chemistry then was similar to that of today, something that no one can guarantee. In Xataka | 4.5 billion years of Earth’s history, summarized in a spectacular video map In Xataka | We thought we had an accurate photo of what the Earth was like 4 billion years ago. Zircons are telling a different story Cover | Virtual Museum of Mineralogy and Gemini with AI

Although there are scientists saying the opposite, it is time to recognize it: continents do not exist

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For a couple of years and from time to time, a very specific type of article has gone viral: one that repeats that there is a group of researchers from the University of Derby has found a new (micro)continent in Davis Strait. That is, between Greenland and North America. And yes, it sounds a little Martian. How could we have lost an entire continent in the 1,143 kilometers that that strait measures? It has its explanation What the hell is a continent? The most intuitive answer is “a large area of ​​land surrounded by water”; But the truth is that it only works in theory and, when we tackle the problem, everything gets complicated. Therefore, if the question is “how many continents are there in the world?”, the only logical answer is this: “it depends.” What do you mean “it depends”? The reasons behind many of the divisions we handle are “purely historical and cultural.” In fact, as Miguel García explains“the educational systems of different countries establish different continental divisions”: In Anglo-Saxon countries, it is most common to say that there are seven continents (Europe, Africa, North America, South America, Asia, Antarctica and Oceania); On the other hand, in Romance language countries, the most common answer is that there are six continents (uniting the Americas into one); Six continents are also explained in the countries of the ex-Soviet orbit (although they keep America separate and what they unite is Europe and Asia). There are more options, of course. For example, we could unite Asia, Africa and Europe on a single continent and, together with America, Australia and Antarctica, there would be four. By proxy, we could even remove Antarctica because, well, without its snow cover it would become an archipelago (whose largest island would be smaller than Australia). It’s time to admit that continents do not exist. They are social constructs, like municipalities or provinces. Hence, as García explainsFrom a geological point of view, it can be concluded that continents do not constitute a scientific concept. In any case, we can talk about tectonic plates (and, although defining their number is also a hassle, we would not talk about less than 15). So what are the Derby researchers talking about? Now it’s time to get into the matter: what researchers have used is something elsethe thickness of the Earth’s crust. In general, there are two types of Earth’s crust: continental (about 35 kilometers thick) and oceanic (between 8 and 10). Of what they have realized is that as the tectonic plates between Canada and Greenland have shifted, the Earth’s crust has been reconfigured. The result has been a protocontinental (i.e. extremely thick) crust on what should be an oceanic crust. And what is all this for? It must be admitted that, once we get the matter down, everything seems more boring. However, the finding is very interesting: we actually don’t know very well how tectonic dynamics work. We have very developed ideas and models, yes; But when it comes down to it, there are more questions than answers. Being able to study in detail the formation of a protomicrocontinent is a unique opportunity to understand phenomena such as the one that is dividing Africa in two. And we have already seen that, unlike what we tend to believe, this has a real impact on daily life of millions of people. Image | Kate Ter Haar In Xataka | A huge crack has opened in Kenya’s Rift Valley and it seems it’s just the beginning This article was originally published in 2025. We have updated its content.

Researchers have discovered “lost continents” from 4 billion years ago

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The idea we have of the early Earth involves a huge ball of incandescent magma and conditions incompatible with life. The problem? That there are no rocks from 4.3 billion years ago to confirm this consolidated theory. What we do have are some microscopic crystals called zircons. And zircons are telling a different story, according to this study by a research team at the University of Wisconsin-Madison. published in Nature. What zircon says. Regarding the behavior of the Earth’s surface, geology valued two ideas for that period known as Hadean: that there was a plate tectonics where one plate sinks under another or that the Earth had a kind of stagnant lid, a rigid and hot surface where heat only escaped through large columns of magma. Well, neither one nor the other, both: zircons leave evidence of an Earth that already had oceans, liquid water and a crust that alternated both systems. John Valley, the University of Wisconsin-Madison geoscientist who leads the study explains that “There were about 800 million years of Earth’s history in which the surface was already habitable, although we have no fossil evidence and we do not know when life first emerged.” Why it is important. Because they determine that the Earth did not choose a single model, but rather that both processes took place at the same time in different places. Of course, it was not a stable plate tectonics like the one that exists today, but rather it had violent and short episodes of sliding of the edges of one plate under another (subduction) that coexisted with large jets of magma that rose from the interior of the Earth. This discovery is key to understanding how the Earth’s surface moved, the formation of continents and life. On the one hand, without tectonics, the felsic continental crust that floats on the mantle and makes up the lands on which we live would not exist. On the other hand, plate tectonics regulates the climate and recycles nutrients, so knowing when it started working helps understand when the Earth became a place compatible with life. How they analyzed it. The John Valley team analyzed the popular zircons from Jack Hills (Western Australia). These sand-sized minerals are a kind of time capsule, housing the only direct record of Earth’s first 500 million years. They were looking for chemical “fingerprints” that would reveal where and how they were formed, for which they used technology WiscSIMS high resolution. They then compared the results of the analysis with other zirconiums from the Hadic Eon found in Barberton (South Africa). Each one told a different story. Surprises in the “DNA” of the mineral. 47% of oceanic zircons had high levels of Uranium compared to Niobium, indicating that they formed in subduction zones where ocean water sinks into the mantle. On the other hand, the South African zircons show that they were born from virgin rock from the planet’s interior, confirming the classic ‘stagnant lid’ theory by which the Earth’s first solid surface was rigid and immobile. Or what is the same: while in Australia the crust sank and created protocontinents, in what is now South Africa the Earth behaved differently, with a rigid and stagnant crust. That is, the early Earth was a mosaic of tectonic styles. The Earth did not go from being hell to what it is today overnight, but rather it was a hybrid process and generated the necessary conditions for life sooner than we thought. In Xataka | We know it as “the red planet”, but 3.37 billion years ago Mars was almost as blue as Earth In Xataka | 4.5 billion years of Earth’s history, summarized in a spectacular video map Cover | Tomáš Malík and Javier Miranda

The “lost continents” of our planet are leaving their trail in an unthinkable place: the earth’s magnetic field

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Life as we know it depends largely on the stability of the Earth’s magnetic field. But this stability (or the absence of this) depends in turn on factors that we still do not understand. Some of these factors are in the outer space, others instead are thousands of kilometers hidden under our feet. From the bottom up. Huge geological structures located in the land mantle They could be contributing To destabilize the magnetic field that protects the land from radiation and particles from space. These are the “sunk continents”, the large provinces of low speed (LLVP). Sunk continents. This last name is due to the fact that these rock masses located in the deep layers of the land mantle stand out from the rest of its surroundings because the seismic waves move more slowly through them. Through this method we know the existence of two large LLVP, one located under the African tectonic plaque and the other located under the peaceful plaque. We do not know exactly what they are or what is the origin of these rock masses. A hypothesis indicates that could be remains of the impact between the primal earth and a second planet called Theia. The Moon would be one of the results of that impact, another would be that part of The remains of Theia would have been “embedded” on earth, specifically in the mantle, giving rise to these “lost continents.” However, other studies have pointed out that these masses would be formed, at least partially of ocean cortex buried through subductive geological processes, which would make them more close to “lost continents” of the surface of the earth. The new study can be linked to this last hypothesis. Fed by a “fire ring.” The team He modeled the movements Convectives of the land mantle, also creating a reconstruction of the possible movement of the tecton plates on the surface of the Earth in the last 1,000 million years. Thus they found indications that the African dough would contain older and more “mixed” than the peaceful mass, which would contain 50% more oceanic crust, a more “young” cortex and different from the surrounding mantle. This could be explained with the call “Pacific Fire Ring”, A vast network of failures, many of them subductive that little by little they engulf part of the earth’s crust. This “banquet” would have been producing for at least 300 million years and would be serving to feed the Pacific LLVP. The details of the study were published In an article In the magazine Scientific Reportsof Nature. In diversity is the key. Until now, intuition pointed out that these two underground “continents” had a similar composition. The reason is precisely that the two slow down the passage of seismic waves in a similar way, which leads us to the intuition of thinking that these are very similar in their characteristics. However, the team responsible for the new work indicates that this may not be the case. The reason is that the temperature is more than the material that makes these regions slow the waves that cross them. The balance is complicated. The formations are more or less opposite in the Terrestrial globe, which in principle is great news: since these masses influence the way in which the temperature of the earth’s core is spread in higher layers, which in turn affects the conductive movements inside the nucleus of the planet. Since these movements are those that allow the existence of a magnetic field On Earth, the way in which they occur has a lot of impact on this field. If the LLVPs are different, the way in which the field is generated ceases to be symmetrical as one would expect, which gives rise to the appearance of imbalances. Discussing the different hypotheses. As we pointed out at the beginning, the new study can be linked to the idea that the LLVPs are the result of the sinking of earth cortex pieces and not the remains of a planet of the original solar system. Although the study does not offer conclusive evidence confirming this first hypothesis, It can be seen as a new more test in this address. In Xataka | Julio Verne was right: there are three times more water in the depths of the earth than in all oceans together Image | Oxford University; Panton, Davies, et al. (2025) / NASA/Goddard Space Flight Center Scientific Visualization Studio

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