Any fan of paleontology or geology knows the K / Pg limit (formerly called K / T), the rock stratum that dates back to about 65 million years ago and delimits the point in the fossil record from which the remains of dinosaur (and those of many other lesser-known organisms). One of the peculiarities of this layer of material is that it contains traces of elements that are not frequent on Earth, such as iridium, but in asteroids. Hence, it is thought that the impact of a body from space contributed to the extinction of the dinosaurs.
Well, it turns out that there is a lesser-known stratum that seems to have been formed by another catastrophe of global proportions … But this happened only a few thousand years ago.
Looking for the responsible
Recent Drias is the name of an episode of rapid global cooling that started about 12,800 years ago and lasted about 1,300 years. The study of the ice that was deposited at this time on Greenland suggests that the temperature dropped to between 2 and 6ºC in the hemisphere north, a decline that would have caused the glaciers to advance and the climate to become drier in this half of the planet. But what kind of phenomenon could have caused such an abrupt change of such magnitude?
The answer seemed to be found in a layer of sediment that was deposited during that same period and that can be found in places as distant as the west coast of the United States, Central America and Syria: the so-called “recent Drias boundary”.
As with the K / Pg limit, the material in this stratum of about 12,800 years contains unusually high concentrations of elements that are more abundant in meteorites than in the Earth’s crust, such as iridium, platinum, nickel, and cobalt. In addition, this layer is also packed with “microtectites” and nanodiamonds. The former are tiny masses of glass that form when the siliceous material melts and cools very quickly, while the latter are small carbon crystals formed at high pressures and temperatures. Be that as it may, the formation of this type of structure requires the extreme conditions that occur at the point of impact of a meteorite or during its explosion in the air.
It should be noted that some characteristics of the Drías Recent boundary could be explained through other less cosmic phenomena. For example, the impact of lightning on the ground can also generate small masses of molten glass similar to microtectites, and certain carbon products contained in this layer were interpreted as debris deposited by the combustion of organic matter. Even so, after analyzing in detail the material of this stratum and verifying that none of these possibilities manages to satisfactorily explain its composition, a 2020 study has concluded that the cause of the anomalous characteristics contained in this sediment layer it could only come from space.
Furthermore, since the material of the Drías Recent boundary is scattered over an area of 50 million square kilometers, it seems that the most plausible explanation is that the Earth passed through a swarm of commentary fragments about 12,800 years ago. As a result, these 10 to 1000 meter diameter ice and rock moles rushed onto our planet, bursting in midair in many different places, and covered part of the Earth’s surface with dust.
One of the places where a greater concentration of remains related to the explosion of a meteorite has been found is the ancient settlement of Abu Hureyra, in Syria, indicating that a comet fragment must have exploded quite close to this place that was inhabited when the catastrophe occurred. Now, although many articles dealing with this topic speak of “a village destroyed by a comet,” I have been unable to find references indicating what exact effects the explosion had on the settlement. In fact, the closest thing to this statement I have read in a scientific article is in a study that concluded that high concentrations of cometary debris «suggest that the effects [de la explosión] on the town and its inhabitants would have been severe».
Now, although the effects of this comet bombardment on the rest of the planet are not as striking as the idea of an ancient town destroyed by a meteorite, these have been quantified: all the dust that remained suspended in the atmosphere after the bombardment caused a sudden drop in temperatures that changed the climatic patterns of the northern hemisphere during the following millennium, contributing to the extinction of many Pleistocene species.
On the other hand, it must be said that the abrupt climate change of the Drías Recent has been tried to explain through other mechanisms, such as an episode of intense volcanic activity, the interaction of our planet with a large solar flare or even the outbreak of a supernova close to Earth. Despite all this, it seems that the cometary bombardment hypothesis is the best explanation for the available evidence … So it is reassuring to know that today we have programs dedicated to detecting comets and near-Earth asteroids.
DON’T NECK IT:
- There are those who maintain that the fall of these comets was the cause of the disappearance of Atlantis. But, as with all the other cataclysms that have been tried to attribute this merit, it is impossible, because Atlantis never existed.
- Andrew M. T. Moore et al. “Evidence of Cosmic Impact at Abu Hureyra, Syria at the Younger Dryas Onset (~ 12.8 ka): High-temperature melting at> 2200 ° C”. Scientific Reports, volume 10, article nº 4185 (2020).
- Ted E. Bunch et al. “Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago.” PNAS, 109 (28), July 10, 2012.