Pyroclastic stratigraphy of the Soufriere Hills Volcano, Montserrat ‐ Implications for the present eruption

Abstract

The stratigraphy of the Soufriere Hills volcano is dominated by dense‐andesite block and ash flow deposits. Forty‐one radiocarbon ages permit a reconstruction of the eruptive history over the past 31,000 years. A single stratigraphic member yielding radiocarbon ages of 22,000 to 20,000 years B.P. is composed of block and ash flow deposits with semi‐vesiculated clasts concentrated in the upper third of each deposit. The present eruption is also producing block and ash flow deposits with both dense and semi‐vesiculated clasts. It marks a return to a more explosive driven type of activity as occurred 22,000 to 20,000 years ago. Deposits of this member have a broad sheet‐like form and volumes in excess of any produced so far by the present eruption.