A favored Conclusion theory to explain the extinction of dinosaurs, together with many other species, has been the globally catastrophic collision of a large asteroid with the Earth. ██████████ ████████ ██ ██ ████████████████ ████████ ███████ ██ █ █████ ██ ████ █████ █████████ ██ █ ██████████ █████ ████ ████ █████████████████ ████ ███ ████████ ██████ █ ███ █████████ ██████ ████████ ████ ███ ████████ ██████ ███ ███████████ ███████ ██ ███ ███████ ████████ ████████ ████ ██████ ███ ███████████ ██ ███████ ██████ ████ ████ ███ ██████████ ██ ████ ███ ███████ ███ ██████ ██████ ██ █████ ████████ █████████ ████████ █████ ████ ████████ ██████ ███ ████ ████ ██████ ██ ███ ████████ ████████ ██████ ███ ███ ████████████
The stimulus presents two competing theories for the extinction of the dinosaurs. The first is the asteroid-impact theory: a large asteroid collided with the Earth and caused a global catastrophe. The evidence for this theory is an extraterrestrial chemical element found in a layer of dust around the world, at a geological level corresponding to the time of the supposed impact and the extinctions.
The second is the volcanic-activity theory: massive volcanic eruptions put enough dust into the atmosphere to cool the planet. The evidence is that the Deccan region of India has extensive volcanic flows from the same time period as the supposed asteroid impact and the extinctions. Proponents of this theory argue that any asteroid impact was irrelevant to the extinctions.
The new theory assumes that
the massive volcanic ████████ ███ ███ ██████ ██ ███ ██████ ██ ██ ████████
Necessary, because if the volcanic activity had been caused by the asteroid impact, the asteroid would be the root cause of the extinctions rather than something irrelevant to them. The entire point of the new theory is that the asteroid did not matter, so it has to rule out the possibility that the asteroid is what set the volcanoes off in the first place.
no individual dinosaurs ████████ ███ ██████ ██ ███ █████████ ██ ██ ████████
The argument is about what caused the extinctions overall, not about whether the impact killed any particular dinosaurs. Whether a few individual dinosaurs survived the impact has no bearing on whether volcanoes or the asteroid drove the mass extinction. The theory can be fully true even if the impact happened and killed some individual dinosaurs, as long as the volcanoes are what caused the extinctions and the asteroid was not the cause.
the extinctions took █████ ████ █ ██████ ████ ██████ ████ ████ █████ ████ ██ ██████ ██ ███ ██████ ██ ██ ████████
The theory makes no claim about how long the extinctions took. You might picture volcanic cooling as a slow process and an asteroid impact as a sudden one, so it can feel like the volcanic theory needs the extinctions to be drawn out. But the theory only needs volcanism to be the cause. It does not need the extinctions to have lasted longer than they would have under an impact.
other volcanic eruptions ████ ███ █████████ ██ ███ ████ ████ ██ █████ ██ ███ ██████ ██████
Whether eruptions were happening elsewhere at the same time does not matter to the theory. The theory needs volcanic activity to have put enough dust in the air to cool the planet, and the Deccan flows are offered as that source. Other eruptions occurring at the same time would, if anything, add more dust and help the theory rather than threaten it. The theory never claims the Deccan was the only volcanism, so it does not need to assume other eruptions were absent.
it is not ████████ ██ █████████ █████ █████ ████ ████████ ██████ ███ ████████ █████ ██ ███ ██████ ██████ ██ ███ ████████ ██████ ██ ██ ████████
The theory does not need the order of events to be impossible to determine. If anything, it would welcome knowing the volcanoes erupted on their own, whether or not we can pin down the sequence. Being unable to tell which came first is not something the theory relies on. Negate this and it becomes possible to determine which occurred first, which does nothing to undermine the claim that volcanoes caused the extinctions.
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