Volcano making people (like me) wish for an easy way to make more types of volcano eruptions that are also realistic. I propose these elements:

PMCE: "Pumice. Formed when lava cools rapidly under pressure. Heavy particles, but floats on water."

Grey powder. Floats on water, but is otherwise identical to STNE, which separates it from SAWD.

PYRC: "Pyroclasts. Light particles that move very easily across surfaces and scorches everything."

Dark grey powder. Moves rapidly downhill and across flat surfaces (even rough terrain), and leaves a trail of dark smoke behind it. Easy to blast in the way you want it to, but hugs the ground from then on. Difficult for it to travel uphill. Like MORT, but moves freely. Sets flammables on fire and, if possible, breaks BRCK and BMTL. (Makes for more realistic pyroclastic flows. BCOL on fire isn't quite doing it).

ASH: "Very light powder. Rises upwards, spreads, and falls."

Grey powder that actually looks like a gas. Only very slight pressure is enough to make it float for a long time. If used correctly, rises upwards in an eruption column, loses updrift, spreads out flat, becomes too heavy, and falls like a light powder, possibly with PMCE. (I know we already have CO2, this was just an idea.)

Hopefully these won't be too hard to implement or too special to have any better uses.