When you burn down a lump of coal the unburnable parts are called “clinkers”. FOr the most part “clinkers” are large chunks, but there’s no rule that says you can’t also include volcanic ash in the category ~ particularly when the same volcano is tossing rocks the size of Volkswagens.
Wow. . .please let me know when a Volkswagon-sized chunk reaches 20,000’. . .that would be something to see, for sure, and probably more dangerous than an Oklahoma hailstorm.