Shadow of the volcano
Out of the blue, and for no immediately obvious reason, the terrible fate of the Roman city of Pompeii once again occupies centre stage. Still 76 years short of the 2000th anniversary of the burial of the town beneath a thick shroud of ash and debris from local volcano Vesuvius, the recent bestselling novel ‘Pompeii’ by Robert Harris is about to be joined by a BBC docudrama.
‘Pompeii — The Last Day’ records the countdown to catastrophe from the perspective of a Patrician uncle and his young nephew, known to history as Roman men of letters Pliny the Elder and Pliny the Younger. Just 17 at the time, the younger Pliny entered the annals of volcanology by providing, in his letters to Tacitus, the first ever description of a volcanic eruption.
Since excavations began in earnest in 1748, progressively exposing a city and its people captured in time as if in a series of cameo photographs, there has been continuing curiosity about the appalling events that began on August 24 in 79 AD and ended a couple of days later. Without doubt this is a reflection of the astonishing and unique snapshots of individuals and family groups, preserved forever in their excruciating death throes by accumulating ash, and subsequently reconstructed in plaster for our edification and wonder.
But why the vogue to revisit the particularly violent and unpleasant ends of Pompeii’s residents now?
Vesuvius has a rather chequered eruptive history, at times rumbling away almost continuously for decades, at others standing utterly silent for centuries before blasting into life with dire consequences for those living on its flanks. The volcano is currently well into another of these rather ominous quiet periods, following years of activity ended by an eruption that contributed in 1944. Since then, the entire Bay of Naples region has been a hotbed of construction — much of it unplanned and illegal — that has increased the number of people living in the danger zone. As a result, an estimated three million people may be affected by the next eruption, with 6,00,000 or more shoehorned into the so-called la zona rossa under serious threat.
Having done little or nothing to restrict development in the danger zone over the past 60 years, the civil authorities are now beginning to worry and have spawned a scheme to persuade the residents of the 19 towns closest to the volcano, including Pompeii, to relocate. The plan is intended eventually to reduce the population of the "red zone" by 20 per cent, by offering $30,000 per family to move to a safer location.
Few people have taken the offer so far, nor are they likely to while the volcano remains silent. Much will depend upon how much warning the monitoring scientists at the Vesuvius volcano observatory can give the civil authorities. Plans assume two weeks, but this poses serious questions. Unlike earthquakes, no volcano ever erupts without warning signs. The ground swells and earth tremors increase in size and number as fresh magma fights its way towards the surface.
Hotspots around the world
There has been recent unrest at a number of volcanoes that have been quiet for decades or even centuries, which suggests that at least some of them can be expected to burst into life in the not too distant future. The following might well be worth keeping an eye on:
The numerous volcanoes located around this small island in the Caribbean’s Lesser Antilles chain have lain dormant for perhaps as many as 28,000 years. But recent shallow earthquakes have raised concern.
Located on the Philippine island of Luzon, Taal is an active volcano in a giant, lake-filled crater formed in prehistoric times. In 1965, an eruption blasted out hurricane-velocity clouds of scalding steam, ash and mud, killing more than 200 people. The volcano has been restless since 1991, with increased numbers of earthquakes and rising lake temperatures.
Over the past two million years, Yellowstone in Wyoming has hosted three gigantic eruptions, each of which formed a giant crater, or caldera. Recently, a large swelling has been detected beneath Yellowstone lake, possibly reflecting an accumulation of steam that may blast a crater through the crust. The area has been closed to tourists.
4. Mammoth Lakes
This part of northern California’s Long Valley caldera has been particularly restless since 1980, increasing worries over a future eruption. Scientists at the Long Valley observatory stress that in any single year the chances of an eruption are small, but agree that recent earthquake swarms, ground swelling and releases of carbon dioxide increase the chances of an eruption in the near future.
5. Three Sisters
Sometime after 1996, the ground surface started to swell in this volcanic region of Oregon. By 2000, uplift had reached 10 centimetres and swelling is continuing at about 2cm a year.
Scientists interpret this as evidence of magma accumulation at around 6-7 kilometres depth and warn that continuation of uplift may lead to an eruption.
6. La Palma
Despite a period of quiescence since its last eruption in 1971, concerns remain over the stability of the Cumbre Vieja volcano on La Palma in the Canary Islands.
During previous eruption in 1949, the western flank of the volcano detached itself from the rest. Catastrophic collapse during a future eruption threatens to devastate the Atlantic rim with giant tsunami.