Since many years from now, the most popular hypothesis to explain the extinction of the dinosaurs 66 million years ago was the one of a meteorite impact against the Earth. But, sometime after it, a new hypothesis arose, as, for example, the one of the eruption of big volcanos. Currently, new studies point at, another time, to the theory of an asteroid impact.
What caused the extinction of the dinosaurs?
66 million years ago, an asteroid of approximately 10 kilometres of diameter impacted against the Earth, causing, in consequence of that impact, the extinction of most of the living beings of that epoch, including the dinosaurs. This asteroid created a crater, which is situated in the region of the Yucatan, which has a diameter of 150 kilometres and a depth of 20 kilometres, the named crater of Chicxulub. The impact provoked an enormous tsunami.
Even if this would be a sufficient reason to affirm that this was the cause of the death of these reptiles, the question isn’t as clear as we could think, as it was discovered that, also 66 million years ago, there had been a big volcanism period on the Earth. An alternative theory suggests that this volcanic activity could be the cause of the extinction of the dinosaurs.
Asteroid or big volcanic activity?
- The first hypothesis sustains the theory, explained above, of the impact of a big meteorite against the Earth, that triggered important environmental changes. This theory permits us to explain the big quantities of iridium that we can find, through all the planet, in the terrestrial mantle layer of 66 million years of antiquity. In this layer we find big quantities of iridium, which suggests that, as we will see later, the particles related to the meteorite, including the vaporised elements, spread rapidly through the Earth’s atmosphere, blocking the sunlight. Then, all this dust, which contained iridium coming from the meteorite, fell onto the Earth’s surface, which still remains nowadays in the geological layer of 66 million years ago. This material is very rare on the Earth’s surface, while in the asteroids it is found in abundance.
- The second theory refers to a big period of volcanic activity, that is situated in the Deccan Traps, which are a big igneous province situated in the central west part of India. According to this theory, the volcanos, which it is thought that in that epoch occupied a 1 500 000 square kilometre area, could have given off big quantities of gaseous compounds, that would have provoked the extinction of the dinosaurs.
The second theory is, each time, the less accepted, and, nowadays, it has already been concluded that the impact of an asteroid was the main reason for the extinction of the dinosaurs. According to an article published in the Science magazine by American professor Pincelli Hull and his colleagues, the volcanism hypothesis doesn’t give us sufficient explanations to be considered as true. In fact, nowadays we know that the eruption of the Deccan Traps took place much time before the extinction of the dinosaurs and the meteorite’s impact. Additionally, the volcanic activity of this zone would have only produced a global gradual warming of approximately 2 degrees, but not a massive extinction. What can be affirmed is that the emitted gases from those eruptions had a lot to do in the moment of giving shape to the different species issued after the extinction of a big part of the living beings of that epoch.
The effects of the meteorite
As we have seen, the source of the death of the dinosaurs was the meteorite, of about 10 kilometres, that impacted the Yucatan region, creating the Chicxulub crater. However, the effects of the impact were varied and occurred in different ways.
It is supposed that, during the first hours that followed the impact, a big part of the territory that occupies North and South America was critically affected, totally devastated. This is due to that, following the meteorite’s impact, many pieces of the Earth’s surface were detached and sent out to the atmosphere. All that dust and rocks fell another time, warming themselves and provoking, consequently, fires in many parts of the planet. The creatures that survived, had to deal with an even more complicated situation: an atmosphere filled up with dust and gases.
The environmental effects that followed all these impacts, were even more lethal than the meteorite itself. A gigantic dust cloud covered all the atmosphere, which blocked that sunlight that arrived on the Earth. This is known as a nuclear winter. Without light from the Sun, there couldn’t be photosynthesis, for which many plants died. Moreover, without sunlight, the temperatures also dropped strikingly, to incompatible levels with life. In this way, only small mammals and birds, which were capable of hiding and feeding themselves from little insects and plants in decomposition, survived the disaster.
This nuclear winter lasted for years, until all the dust and small particles fell another time to the Earth. There is evidence that, throughout all the planet, there was a quick and massive extinction of the living beings, including, among them, the dinosaurs.