Its definitely one of those things where every once in a while I'll be reading about some historical figure and remember that they'd never been able to hear of dinosaurs.
Right?
https://en.wikipedia.org/wiki/Deccan_Traps
https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
I don't think we definitively have the answers to that question IRT what killed the dinosaurs.
Well, in the sense that we can never be sure of anything, yeah. But it not being enough is a really extraordinary idea.
Then the Chicxulub crater was found and dated to basically the exact same time as the K-T extinction event to within experimental error. So I guess the asshole was right?
Except science doesn't work by smoking guns, as appealing as that would be. There are a lot of contradictory evidence. Better instruments and more careful data collection shows that in some places the fossil record stops prior to the impact layer. Also the fossils are of animals you would expect of an extinction event already ongoing. Oh, and coincidentally right before the Chicxulub impact India hit the continent of Asia and the Deccan Traps started spewing CO2 and other gasses into the atmosphere in volumes that put human-caused climate change to shame. The ocean was acidifying and ecosystems collapsing. Is it really fair to say an asteroid impact killed the dinosaurs, when they were already on the way out?
IMHO the current best theory is the "one-two punch" that the Deccan traps eruptions basically put every large species on extinction watch, then the asteroid impact happened and finished the job. But it has become so political within that research community that people just aren't rational about the evidence, on either side.
Eh, that's underselling Luis Alvarez a bit. He wasn't just "a physicist," he was a Nobel laureate and arguably one of the twentieth century's few Renaissance men. My favorite Alvarez hack was when he used muon imaging to 'X-ray' the Great Pyramid. He didn't find any hidden chambers, but later researchers did.
In the Alvarez mass-extinction hypothesis, he simply followed where the evidence led, unlike the supposed professionals in the field.
Except.. there are a lot of iridium layers in the geologic record. These things tend to happen every 10-20m years. The most recent is probably the Eltanin impact about 2.5m years ago. The K-T impacter is definitely one of the largest, but not by as much of a margin as you might think. The mere presence of an impact within a million years or so of the mass extinction is neither surprising nor damning evidence, and Alvarez never bothered to make the case beyond that.
And if you look at the history of mass extinctions, most of them are triggered by climate changes from geologic events. Pretty much every time there's massive vulcanism, most of the species on Earth die out. And hey, what do you know, there was a truly epic scale volcanic eruption going on for millions of years right at the same time! What a coincidence.
The Chicxulub impact is certainly part of the story of the extinction event that killed off the dinosaurs. But the evidence isn't there to assert that it is the whole, or even the most important part of the story.
Alvarez looked at the global iridium layer 66M years ago and said "This is from an impact. I don't know where the crater is, but there is one and when we find it, it will be X km big and date to 66M years ago." Then the Chicxulub crater was found and matched his predictions to a T. That is a hell of an impressive scientific accomplishment. Which may or may not have anything to do with the K-T extinction event and the end of the dinosaurs.
To your question, my understanding is that if you ignore the K-T asteroid impact and look at the fossil record up to but not including the iridium layer, it looks very similar to the P-T die off. Same early indicators, same die-off patterns (e.g. starting with single celled marine organisms, changeup of specialized niche species, acidification, ecosystem collapse, more fungi etc.) Then of course the impact happened and reshaped everything. BUT, the argument goes, the impact had such drastic effects on Earth life because basically all the existing ecosystem slack had been taken up by the downstream effects of the Deccan Trap eruptions.
IMHO the researchers like Gerta Keller who push the Deccan Trap only theory are mainly butthurt about Alvarez. But if I were to steelman their position, it is that a P-T like extinction event was already clearly underway, and if the asteroid impact hadn't happened we would have seen basically the same die off over a slightly longer period (or if the impact had happened without the Deccan Trap eruptions, there'd have been enough resilience that maybe the impact wouldn't have caused extinctions?), and so we should assign causality to the volcanos. Hard to prove a hypothetical though, which is why I think the one-two punch explanation is better science.
Edit to add: checking Wikipedia, I see that chemists Frank Asaro and Helen Michel are also credited as part of the core team, although it still gets called the "Alvarez hypothesis".
Up to that point, it was a matter of belief among paleos that bolides were not a significant factor in the history of life. Essentially, that the Earth did not experience frequent or significant impacts after the initial formation of the solar system.
The evidence supporting Alvarez became so compelling that it not only became accepted as the K-T cause, it opened the door to considering bolides for all sorts of previous extinctions--an idea explored by Raup in his book Extinction. It made "sudden catastrophes" acceptable as a serious research subject for the first time since Lyell.
Prior to Alvarez, it was a matter of faith that the K-T boundary must have a solely terrestrial explanation, and the Deccan Traps were elevated to the most likely candidate. But it just shifted the need for explanation--why was there sudden globally catastrophic vulcanism? You say "India hit Asia" but that was not a sudden thing, in fact it's still happening today. Hot spots are still active today. It never really worked, but it was the best they had (or were willing to consider at the time).
I think you are exhibiting exactly the problem with the Alvarez hypothesis that makes people have such a gut reaction to it. It is a Deus Ex Machina that can be invoked at any time to explain a die off even in the face of conclusive evidence to the contrary.
Calling something that actually happened a “Deus Ex Machina” seems like a hint that you might not be coming to this conversation with the most objective mindset.
There was a revision to the book (not sure the date) with changes to the text and an expanded author's note at the end that talks about the new things we understand about dinosaurs including how Brachiosaurus are no longer believed to have spent their time in water to support their weight and how it's now believed an asteroid killed off the dinosaurs.
Kind of funny, that now due to astronomer's shenanigans, we're back in the same position.
At some point, well into his accumulation of Dino facts we read an old book I had as a kid (mid 80s) and the book says all kinds of weird stuff I forget but abruptly ends with “they went extinct and we may never know how” and my son (age 4 at the time) is at a loss for words, “it was a asteroid dad, what dummy wrote this book?” For weeks he’d randomly look at me, “hey dad, remember that book that didn’t even know how dinosaurs went extinct? Sigh with disappointment.”
I hadn’t realized this was such a contemporary discovery that it wasn’t even part of my own initial understanding and education on the topic.