Clinker: a sound freed from certain kinds of stone when you walk through it. It transforms the energy of your walking into music, then lies still as your energy shadow passes, only to clink when someone (or something) passes by again. The sound a slope makes is a good indication not only of the type of rock it is formed of (clinker) but of the stability of the slope. The more clinking a footfall makes, the more likely it is to make you fall.

Gerðuberg and Ytri-Radamelskulúr Volcano, Iceland