Shaken, but not stirred : the 2004 eruption of the Tristan da Cunha volcano

Overnight on 29-30 July 2004, Tristan da Cunha, a remote volcanic island in the South Atlantic Ocean, was shaken by an intense earthquake swarm. The tremors felt by many of the island’s population evoked memories of events leading up to the 1961 volcanic eruption and the subsequent evacuation of the whole island. Shortly after this, fresh pumice was found floating near the island. Concern was immediate, and the population watched the site of the 1961 eruption, known locally as “the volcano”. Administrator Mike Hently sought advice from the UK’s Foreign and Commonwealth Office - Tristan is a dependency of the UK Overseas Territory of St. Helena - requesting a scientific assessment of the situation. It was in direct response to this request that the author visited the island in September 2004. Events were reconstructed from the islanders’ accounts and, following requests from the local community, reassurance and advice were given. Both direct observations and subsequent analysis of seismic data are consistent with a small parasitic eruption having occurred on the lower (submarine) flanks of the Tristan volcano, whilst the sub-aerial portion of the volcano had not stirred. This event reiterates the responsibility of the scientific community to provide meaningful advice on potential hazards and hazard mitigation to those living with active volcanoes. It also illustrates the disproportionate vulnerability of small, remote island communities to natural hazards.