The 1902–1905 eruptions of Montagne Pelée, Martinique: anatomy and retrospection |
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| Authors: | Jean-Claude Tanguy |
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| Abstract: | The 1902–1905 activity of Montagne Pelée represents a moderately large eruptive cycle typical of a subduction zone volcano. It followed a three-centuries-long repose interrupted only in 1792 by two small phreatic explosions and minor (phreatomagmatic?) eruptions in 1851–1852. The volcano decidedly awakened in early 1902 with increasing fumaroles at l'Etang Sec summit crater, light earthquakes and phreatic activity from 23 April onwards. On 2–3 May the eruption became phreatomagmatic and much more active. Destructive lahars culminated on 5 May and during the night of 7–8 May, causing 23 casualties at the Guérin factory and about 400 others at Le Prêcheur. On 8 May at 08:02 local time a climactic ‘nuée ardente’ destroyed the city of Saint-Pierre, 8 km south of the crater, and killed all its 27–28,000 inhabitants but one, or possibly two. Testimonies from eyewitnesses of this event, calculations made on its effects, and careful studies of its deposits support the interpretation of a powerful lateral blast (175−140 m/s) accompanied by a fast-moving pyroclastic flow which was directed N-S, i.e. toward the town itself. The temperature of the flow decreased from that of the acid andesite magma (about 900°C) at the crater to 400–200°C as it reached Saint-Pierre. Climactic ‘pelean’ eruptions, initiated by strong explosions, were renewed on 20 May and 30 August. This latter produced 1,000 additional victims at Morne Rouge, making a total of about 29,000 victims for the entire eruptive period. Less violent eruptions, without major explosions, took place on 26 May, 6 June, 9 July and from late 1902 to July 1905, generating slow-moving pyroclastic flows (50 m/s or less), linked to relatively quiet dome growth.The catastrophe of Saint-Pierre resulted from an insufficient knowledge of volcanic hazards at the time and particularly from the total ignorance of pyroclastic flow (nuée ardente) phenomena. Future hazards in Martinique include the renewal of pelean eruptions and widespread plinian activity, such as has occurred in the past 5,000 years, together with a less probable sector collapse triggering tsunami. As major magmatic eruptions of Montagne Pelée may be separated by repose periods of more than 500 years, a long-term instrumental surveillance of the volcano is needed, and adequate concepts in urban planning should be developed and sustained in the next centuries. |
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