Lahars, or mudflows of volcanic material, are very common in high rainfall areas. They form from fresh ejecta, which is still hot, mixed with water or cold ejecta which is mixed with rain water or surface water. They are very mobile, poorly bedded, with occasional layers of crossbeds and have poor sorting. They characteristically form hillocks, ranging in size from a few meters to tens of meters, with a core of boulders. They sometimes have fine basal regions and can be indistinguishable from ignimbrite deposits.
Debris flows consist of highly concentrated, high density material.
Avalanche deposits can also resemble ignimbrites. They usually form from very viscous, acidic lavas which are almost solid when ejected. They resemble ignimbrites and are best distinguished by their overall geometry. Two types of pyroclastic deposits are recognized, pyroclastic flow deposits and pyroclastic fall deposits. Pyroclastic fall deposits usually have good sorting and cover vast areas.