The main evidence for the culprit behind the most recent mass extinction 65 mya is a sediment layer rich in the element iridium, which essentially blankets much of the planet. Earlier extinction events probably had different causes (than an asteroid which had iridium as a minor component). The iridium itself most likely did not contribute to the extinction.
About 252 million years ago, the world came even closer to a complete reboot, in an event called the Permian-Triassic “great dying”. No asteroid this time. Recently, a sediment marker has been found for that particular event which also tells us something about the physics of anomalous geothermal heat - the element nickel http://www.newsweek.com/huge-siberian-eruptions-caused-mass-extinction-and-left-signature-rocks-677017 The nickel itself wasn't responsible for the extinction event according to the “experts” — since the element found in older sediment is thought to be coincidental to the heating event, sort of a natural marker. Are they correct? Of course, one detail not considered by these experts is that the huge amount of carbon dioxide released into the atmosphere, warming the entire planet by 14 degrees, could have been augmented by formation of dense hydrogen as well as LENR under heat and pressure. This source of extra heat first converted carbon and water into CO2 and UDH, some of which now makes up the core of the planet where it continues to react with other elements. Steven Jones when at BYU found greatly elevated levels of He3 - helium-3 around volcanoes and hydrothermal vents - and coined the term "piezonuclear fusion" to indicate fusion caused by mechanical squeezing. The theory becomes more valid with the proper identification of a species: ultra dense hydrogen (Holmlid) being present… and hot rock containing nickel (and iron oxide) would help to catalyze the UDH and the fusion. Fast forward a few eons and Italy's Campi Flegrei Supervolcano has recently been reported to be active once again. Elevated helium-3 is the evidence, and this is a risk that almost no one seems to know much about. https://www.sciencealert.com/the-first-supervolcano-eruption-in-our-lifetime-could-be-closer-than-we-think Sad to imagine that the proof of LENR could eventually come from delving into a mass extinction event. At least Italy has many physicists who understand and believe in LENR.
