The Chicxulub crater off the top of the Yucatan peninsula is attributed for that particular event. It wasn't really known until the early/mid 90s I don't think.
Right. Although even after the discoveries related to the K-t boundary and the crater, there was a school of thought that it was just a contributing factor to a pre-existing general decline. My understanding is that there's now a general consensus that it was much more of a singular cataclysmic event.
There's still a substantial group that thinks the impact was part of a 1-2 punch with the eruptions of the deccan traps, which produced a far larger impact on the atmosphere but over a longer period of time. Iridium from the asteroid impact is found in the basalt deposited by the deccan traps, so they definitely happened concurrently.
That said, if you look at the patterns of extinction, survivors seem limited to things that could hide in burrows or in deep water and then survive for an extended period exclusively on scavenging, as if everything that happened to be on the surface was suddenly killed and then photosynthesis stopped working for a few years. Notably, species that would normally be very sensitive to climate change like small amphibians survive whereas generalists capable of long distance migration die out. There may have been ecological stress beforehand but a singular cataclysmic event turned it into a mass extinction.
Do we know for sure that the volcanism in the Deccan traps wasn't caused/triggered by the asteroid impact? I know they're pretty much located at the opposite ends of the world, so could the shockwaves from the initial impact have created an amplified node at the other side?
(edit: wikipedia[0] says it's inconclusive:
> Although the Deccan Traps began erupting well before the impact, [..] the impact may have caused an increase in permeability that allowed magma to reach the surface and produced the most voluminous flows, accounting for around 70% of the volume
While there are many large igneous provinces similar to the deccan traps (for example the siberian traps associated with the Great Dying), we don't really have any good evidence for large asteroid impacts comparable to chicxulub so it's tough to say with confidence what effects were directly the result of it versus coincidental.
The Great Dying you speak of happened to coincide with an asteroid crater off the coast of Antarctica [0]. I haven't been able to find an accurate globe of the continents at that time ([1] doesn't show the poles in great detail), but it does look like eastern Siberia was at the antipode of the Australia/Antarctica boundary. So the theory seems to hold up -- at least from the confines of my armchair, that is.
IIRC, oil and gas companies knew of the crater, but that knowledge was for many years proprietary information belonging to Mexico's state-owned oil company Pemex who paid significant money for the geological studies of the area.
