pyroclastic（adj.）
在地质学中，“由火山作用形成”，特别是指火山爆发中快速移动、密集、超热的火山灰、气体和岩石； 到1862年，指的是由此产生的岩石； 见 pyro- “火”+ clastic，表示“破碎成碎片”。
The word "ash" is not a very good one to include all the mechanical accompaniments of a subaerial or subaqueous eruption, since ash seems to be restricted to a fine powder, the residuum of combustion. A word is wanting to express all such accompaniments, no matter what their size and condition may be, when they are accumulated in such mass as to form beds of "rock." We might call them perhaps "pyroclastic materials," but I have endeavoured in vain to think of an English word which should express this meaning, and believe, therefore, that the only plan will be to retain the word "ash," giving it an enlarged technical meaning, so as to include all the fragments accumulated during an igneous eruption, no matter what size or what shape they may be. [J. Beete Jukes, "The Student's Manual of Geology," Edinburgh, 1862]
“灰”这个词并不是一个很好的词来包括所有的亚空气或水下爆发的机械伴随物，因为灰似乎仅限于细粉末，即燃烧的残渣。需要一个词来表达所有这些伴随物，无论它们的大小和状态如何，当它们积聚成为“岩石”层时。也许我们可以称它们为“火山碎屑材料”，但我一直徒劳地想着一个能表达这个意思的英语单词，因此相信唯一的计划将是保留“灰”这个词，赋予它一个扩大的技术含义，以包括在火山爆发期间积累的所有碎片，无论它们的大小或形状如何。[J. Beete Jukes，“地质学学生手册”，爱丁堡，1862年]
该词起源时间：1862年