When Juan Antonio Sánchez Garrido decided to start studying the geological formation of the Gordo Megabed with his partner Sebastian Sanchez Neither of them imagined that this immersion in the depths of the Almeria earth would lead them to discover the first meteorite impact in Spain. Although this set of rocks from the Tabernas basin was well studied as a result of seismic activity, they detected some parameters that did not add up.
From the chemical composition of the rocks to their magnetic activity, everything seemed to indicate that, beyond a seismic movement, 8 million years ago, something caused an immense increase in temperature and pressure. So immense that it could only fit a nuclear explosion or a meteorite. The first was not likely, given the dates. The second would be a milestone in the science of our country. Thus began an investigation process to which new partners were added and which is still ongoing.
You want to know everything possible; But, at least, the international scientific community has already confirmed that their intuition was going in the right direction: when they made that discovery they were facing the first impact crater of a meteorite that has ever been detected in Spain.
The pieces that were building the puzzle
The first thing that caught the attention of Juan Antonio Sánchez Garrido and his companion was the presence of a geochemical anomaly in relation to platinum group elements. Their proportion was much more consistent with what has been found in impact craters elsewhere than with the geology of a place that has undergone strong seismic activity. In addition, they found splinter cones, striated and conical fracture surfaces found in rocks that have undergone very high pressure, such as those generated by a meteorite upon impact with the Earth’s surface.
As if that were not enough, given that this area 8 million years ago was 20-30 meters deep under the sea, avalanche sediments characteristic of impacts in the water were formed.
They also found magnetic anomalies that only occur when the Earth is subjected to very high temperatures. The impact of a meteorite can raise the temperature up to 2,000ºC. Furthermore, by following these anomalies they were able to delimit where the impact crater and the region that was fragmented around it would be.
Everything seemed to indicate that they were facing a meteorite impact, but of course, a crater like this had never been found before in Spain, so the experts are not sufficiently trained. “The geology that at least they taught me at the University has nothing to do with the geology of disorder, which is the geology of impact,” says Sánchez Garrido.
This made them decide to contact swedish scientistssince several craters of this type have been found in Sweden, so its researchers are much more trained in this regard than in Spain. These supported their suspicions and pointed out that, with high probability, they were facing an impact crater.
The edges of the crater correspond to mountains
Why aren’t there more impact craters in Spain?
In general, it is complicated find impact craters on Earth. The geological activity of our planet erodes or directly buries the traces that meteorites may have left when they collided with our planet.
In Spain, this is the first, although in Azuaranear Zaragoza, there has also been one who has remained a candidate for many years. The difference is that, while in Almería more and more features have been found that lead to the impact of a meteorite, in Azuara these have been scarce. Everything mentioned above has supported the idea that what has been found in the Tabernas basin is an impact crater, although when asking Sánchez Garrido about the decisive evidence he begins by pointing out the presence of planar deformation features (PDFs).
Known in Spanish as planar deformation features, they are microscopic deformations that occur in minerals such as quartz due to a large impact. In turn, quartz minerals that have these deformations are known as shocked quartz. “We have quite a few of these shocked quartz, not as many as we would like, but we know that they are impacted.”
Precisely for this reason, excavation is currently continuing in the crater area. The University of Almería, to which Sánchez Garrido belongs, is working together with the Astrobiology Center and the National Institute of Aerospace Technology (INTA). After 10 days from the time of the interview, they will begin to analyze the results of the survey, in which tubes of perforated rock, called cores, are being extracted to look for more deformations in the quartz and other features that not only reaffirm the origin of the crater. They can also give more information about him.
Juan Antonio Sánchez Garrido next to the extracted rock cores.
In any case, for Sánchez Garrido, this should not be the only impact crater in Spain. And not only because of the suspicions in Azuara. In general, he considers that if scientists in Spain were more familiar with this type of rock characteristics, perhaps many more could be found. “As I told you, the geology that we have been taught at school and even at the University has nothing to do with the geology of the impact, so it takes a long time for that to be seen.” “I think with all certainty that there may be another, what happens is that it has not yet been lucky enough for someone to have had that perspective and begin to study it.”
Furthermore, he insists that these types of structures are often found by pure chance. “On the Chicxulub peninsula, the meteorite crater that extinct the dinosaurs It was found because in the drilling they were doing in an oil field they found a series of layers of materials that did not fit.” There were also the famous shocked quartz, so “they were pulling the thread and also deduced the existence of impact craters.”
A reconstructed history
The impact crater is 5 kilometers in radius, along with a fragmented area that reaches 24 kilometers in radius. It has been calculated that the meteorite must have measured about 800 meters. The impact would be immense, with consequences far away. In fact, according to the researcher we interviewed in Xatakamany geological anomalies have been detected in the area that occurred precisely 8 million years ago. “Many colleagues have studied geological anomalies in the Sierra Nevada that occurred 8 million years ago, possibly due to the same impact.”
This meteorite was much smaller than the one that wiped out the dinosaurs; but, even so, the consequences must have been devastating. “The car is about 800 meters in diameter, so an earthquake of magnitude 8-9 occurs and everything disappears,” the expert reconstructs. “In kilometers around, everything changes: the geology changes, the climate also changes in many kilometers around, very strong winds are produced… That is a pretty strong shock and from there we start again.” However, living beings did not collapse as we might imagine.
Sánchez Garrido explains it with a study carried out by some colleagues who focused on the analysis of fossilized corals. The impact zone, now in the middle of the desert, was then under the sea. Therefore, corals can serve as clues to what happened at that time. A layer of organic materials corresponding to the growth of corals was found, then a layer of sediments derived from the impact, and then more organic matter.
This is because the crater formed, according to measurements made by Sánchez Garrido’s team, in about 7-7.5 minutes. In geological terms it is very little. The life that was influenced by the impact was buried, but what was left alive around it continued to grow immediately, like corals. If it had been a more gradual process, more adaptations would have occurred.
We have the crater, but where is the meteorite?
At the moment, no trace of the meteorite. “We have not yet seen pieces of the car, which melts at the moment,” he clarifies. “Depending on the car, in many cases it melts at the moment of impact, explodes and joins with the materials it melts.” This is precisely what gives rise to platinum anomalies. There are many more elements than expected, because they come from the meteorite. So no, no, they have not found fragments, but they have found the rock with which it was melted.
Now we just have to wait for the analysis of the rock cores that have been extracted in the excavation. This story has waited 8 million years to be told and, for now, we only have the prologue. Surely it can still give us many more interesting data.
Images | SEA
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