Epiclastic pumice deposits are superimposed on the paleosoil covering the Upper Yali pumice layers in the SW sector of the island; these are deposited over shallow sea and subject to the movements of the wind (rounded clasts, cross-beded strata, dunes, marine organism shells). Maximum thickness reaches 8 meters.

In places, these deposits are covered by paleosoil rich in ancient pottery fragments and obsidian chunks, remnants of the Neolithic and subsequently of the classic age human activity, when the islet was inhabited.

Three epiclastic pumice layers are observed in the topmost part of SW Yali; these are overlaid on the paleosoil that contain traces of Neolithic inhabitation.

These pumice layers are no different petrochemically than the underlying pumice layers. However, their local presence makes the occurrence of volcanic events in Yali during the Neolithic age probable.

Unfortunately, no materials have been found so far that could permit dating of the genesis of these layers, nor positions where these formations are found in situ. Hence, the question regarding some very recent volcanic activity in Yali remains unanswered.