HJ Melosh of Purdue University has written a paper on impact cratering – and the role of shocked quartz in determining if a meteor was involved, or not. He centres his research on shock metamorphosed minerals, such as quartz, which is thought to be a key signature of extraterrestrial impact events. Shcoked quartz, it seems, can also be created by lightning. See http://onlinelibrary.wiley.com/doi/10.1002/2017GL074840/epdf
Geologists have long applied the term fulgarite to patches of glass on exposed rock surfaces, or glassy hollow tubes that form in sand. Fulgarites can also form in clays. Fulgarites are fromed by electrical discharges and their origin is not controversial. Lightning is a common phenomenon. Shocked quartz is not as simple. Can lightning create the kind of high temperatures such as occur during meteor strikes? The full paper can be downloaded from the link above. It is just five pages long.
This is also taken up by the Creationists once again, courtesy also of Robert. See https://crev.info/2017/07/lightning-fries-impact-theory/ … where we are told that for generations geologists have looked at shocked quartz as an unambiguous sign of an impact, largely without questioning the theory. Only the pressure and heat of an impact would produce shocked quartz, was the mainstream view. The new paper says that lightning can also create shocked quartz – even quite ordinary lightning. Super thunderbolts are not necessary. There are no Creationist points made in the article and definitely no mention of the Flood. The author seems to accept the actuality of past extinction events (not one event) with an origin in space.