Lahar

Such a highly destructive mud-flow (termed a lahar) eventually stops as a pile of debris of all shapes and sizes, as mixed up as a glacial moraine; the two deposits have often been confused.

Pyroclastic flows are often difficult to distinguish in outcrops from a similar type of fragmental debris flow known as lahars. Both are characteristically unstratified and unsorted. A deposit containing blocks of varied compositions with rounded shapes is more likely to have been formed by a lahar than by a glowing avalanche.

A regime of persistent lahar activity results when eruptive activity continually supplies unconsolidated volcanic material for remobilization.