Jackie - I apologise if somebody answered your q elsewhere in this thread - had a quick look but couldn't find one...

I think the word that was buzzing around your head may have been "scoria" - it's easy to see why "scree" may have popped out instead.

Scoria is a generic term for all the bits of sh** that are chucked out by a volcano - and in particular (pun intended), the smaller stuff. Pumice and volcanic "ash" are examples of scoria.

stales