Ignimbrite is a violent and often deadly rock type. Ignimbrite is a deposit of a pyroclastic flow (extremely hot mixture of gases and volcanic particles flowing down the flanks of a volcano). It is often welded (hence the synonym welded tuff) but not necessarily. According to the Glossary of Geology, all kinds of pyroclastic flow deposits are ignimbrites.
‘Ignimbrite’ is also a nice and intriguing word. It is a combination of latin words ignis (fire) and imber (rain). But the latter word could easily be replaced with nimbus (cloud) as well. I don’t know what is the deal actually. Often used synonym of a pyroclastic flow is nuée ardente (burning cloud in French). Maybe this is an accidental ambivalence? Or is it deliberate and therefore very clever find for this volcanic phenomenon? Or is the etymology of an ignimbrite misinterpreted and actually it was originally thought to be ignis+nimbus. There is even a fourth possibility that the words imber and nimbus are so closely related in Latin that basically these are two slight variations of the same word.
It would be nice if someone more familiar with Latin or the etymology of geological terms could clarify this issue.
Ignimbrite is a rock type – a deposit of a pyroclastic flow.
Welded ignimbrite with pumice fiamme from Gran Canaria. Width of sample 9 cm.