The solid flying debris from a volcano is called tephra.

Here's a breakdown of different types of tephra:

* Ash: Fine particles, less than 2mm in diameter.

* Lapilli: Pebble-sized fragments, 2-64mm in diameter.

* Blocks and bombs: Large, angular (blocks) or rounded (bombs) fragments, greater than 64mm in diameter.

So, the answer is tephra.