Destruction of St. Pierre, Martinique, by ash-cloud surges, May 8 and 20, 1902

St. Pierre, Martinique, was destroyed by ash-cloud surges on May 8 and 20, 1902, that developed from the tops of block and ash flows derived from Mount Pelée. The dome was small during these eruptions, and eyewitness accounts indicate that the eruptive sequence started with vertical eruption columns followed by pyroclastic flows. The flows were topographically controlled and moved down the valley of the Rivière Blanche. Their associated ash clouds expanded to several times the width of the associated flows, and it was these expanding ash clouds that overwhelmed St. Pierre on May 8 and 20. It is our conclusion that the early nuees ardentes of the 1902 eruption of Mount Pelée were formed by column collapse into the crater and not, as commonly stated, by dome collapse or directed blast. The resultant mass poured through a cleft in the southwest side of Pelée, thereby heading the flows in that direction. It was only the later nuees ardentes that appear to have been directly affected by the presence of a dome.