Wednesday, August 21

Vulcano – fiery furnace of the gods

0

La Fossa Crater at a distance in its magnificence.

OF all natural phenomena, a violent volcanic eruption is by far the most spectacular. Perhaps only a nuclear-bomb can rival this.

Each has a devastating effect on both local and more distant people. The flowing lava rivers, pyroclastic deposits, gigantic clouds of sulphur dioxide, carbon dioxide, hydro-chlorine gases and steam, all combine in a volcanic eruption to create gigantic clouds.

One can understand that such an event comes close to mankind’s concept of hell, high water and angered gods.

The ancient Romans in their myths and legends tried to explain the volcanoes of the Mediterranean Sea. They cited the forge of Vulcan — the blacksmith god – beneath the then small island of Vulcano in the Tyrrhenian Sea, just north of the Italian island of Sicily.

There, at his anvil, Vulcan fashioned Jupiter’s thunderbolts, Diana’s arrows and the shield of Achilles. The fire and smoke came from the chimney of his forge (volcanic vent) and the frequent subterranean rumbles and local earthquakes were occasioned by the hammer blows from Vulcan’s forge.

The pleasures of a hydrothermal mud bath.

Thus, the Cratere de La Fossa on Vulcano island is the prototype of all volcanoes. What’s so special about this small island?

As a geomorphologist, I have seen evidence of Plinian, Strombolian and Vesuvian types of volcanic eruptions in my travels but never the results of a Vulcanian eruption until I witnessed it at first hand in a recent stay on Vulcano.

This island has an area of 22 sq km and is one of the seven Aeolian Islands. Another of these islands, Stromboli, known as “the lighthouse of the Mediterranean”, is a slightly more active volcano than Vulcano, spewing material from its central vent high into the atmosphere. It is best viewed at night.

Like the islands of Java, Bali and Lombok, these seven Aeolian islands are sited in a volcanic arc, extending 200 km, having emerged over the last 250,000 years with even older underwater volcanoes in the vicinity.

These volcanic islands were created by the collision of the lighter Eurasian Plate and the slightly denser African plate. The latter plunges downwards along an inclined plane into the subduction zone.

This slow movement downwards generates heat through friction, thus melting the surrounding rocks into magma which then rises upwards to break through the surface of the Mediterranean’s seafloor.

Gradually the lava cools and accumulates and as more and more magma breaks out until the islands rise above sea level. The subduction zone extends to approximately 400 km beneath the Tyrrhenian seafloor.

Fortunately, my hydrofoil journey from the Sicilian port of Messina to Vulcano, although three hours long, stopped to drop off and collect passengers from the nearby volcanic islands of Panarea, Salina, and Limpari bypassing Stromboli a mere 12 km away.

To observe the differences in volcanic structures of these islands was an absolute dream come true! Like the tip of an iceberg, Vulcano’s true beauty is more than skin deep, for although it reaches a maximum height of 500 metres, it extends one kilometre below mean sea level.

Complexity of Vulcano’s  history

Visiting Vulcano was truly an eye opener for me as travel guides seldom include geological details, probably because not too many tourists would be interested in such.

Viewing volcanoes does not reveal their complex formation but fortunately, a visit to the amazing Vulcano Volcanological Centre greatly assisted me in learning about the development of the landscapes I could see with my naked eye.

On this island are five main volcanic creations. The first volcano was initially formed between 120,000 to 100,000 years BP (before the present) by a series of strata-like layers of lava flows between layers of volcanic explosive ashes.

This original volcano had a diameter at sea-level of five km and reached a height of 1,000 metres! The next volcanic feature, the Piano Caldera, was created about 100,000 years BP owing to such a violent eruption that it caused a collapse into the empty magma chamber below, leading to a huge depression.

Subsequent eruptions between 99,000 to 50,000 years BP filled up this crater. Only 24,000 to 15,000 years BP, a series of lava flows led to a further collapse which created the La Fossa Caldera. In the middle of this crater today, there is an active secondary cone, dating back to 6,000 years BP.

It was from August 1888 to May 1890 that the La Fossa cone erupted scattering volcanic bombs all over the island.

The northern tip of the island has a separate, smaller cone named Vulanello which formed initially as an independent island 2,200 years BP. It last erupted in historic times in 1550 AD, depositing large quantities of pyroclastic debris between itself and Vulcan.

These deposits form an isthmus connecting both islands with black sandy beaches. Today a main road links the new with the old!

Today’s volcanic activity

Fumaroles (gaseous emissions of carbon dioxide and other gases) and solfataras (emissions of sulphur dioxide) may be seen daily on the rim and within the La Fossa Crater.

Spectacular rock coloration may be seen there as the gases condense. This crater has experienced massive landslides on its outer walls with more yet likely to come.

An uprising of hot sulphurous fluids creates a hydrothermal system in a mud pool near to the main port. The grey mud bath, with its allegedly healing properties, becomes a tourist hotspot as hydrogen sulphide bubbles up to the surface.

Alongside this mud bath is a small cone of sulphurous evaporite deposits not unlike that surrounding the Old Faithful Geyser in The Yellowstone National Park, Wyoming, USA. Within a couple of km of the La Fossa Crater sulphurous smells may still be detected.

Vulcano’s latest and oldest inhabitants

Today, the island’s real population is relatively small but boosted by its tourist invasions until October-November. Even in mid-September, the daily temperature reached 30 oC plus in a truly Mediterranean type climate.

The weathered volcanic soils provide nutrient rich environments for agriculture and especially grape growing. Fishing for tuna, anchovy, octopus, squid, gurnard and swordfish also takes place.

Tourism is the fastest developing industry with its abundance of hotels and restaurants and consequent tourist shops selling volcanic stones of sulphur, pumice, obsidian and scoria.

Just to sit on the volcanic black sand beaches or the boulders and stones, emitted by previous eruptions, and to marvel at the sheer beauty of the landscape is enough for me!

Geckos abound, as do black ants nesting in the volcanic sands. To see a 45 centimetres slim, black snake slithering quickly across the black sand under my veranda did disturb me but I was assured that there are no venomous snakes on the island.

The geckos thrive on their mosquito kills at night and no doubt the snake on geckos. Cicadas chirp at noon and dusk.

Bougainvillaea covers walls and I have never seen such a variety of coloured hibiscuses and prickly pear cacti in all my life. The bare volcanic outcrops offer precarious holds for niche vegetation while Mediterranean pines with their huge seed cones provide shade for animals, birds and insects.

Kites soar high into the sky and the inevitable seagulls swoop down around the coasts.

Next eruption on Vulcano?

A sophisticated monitoring plan is in place to record minute by minute in real time the physical, chemical and geological characteristics of volcanic activity.

Automatic instruments detect rising magma movements within the main volcano. Changes in temperature, the composition of thermal waters and the emissions from fumaroles and solfataras are analysed in order that advanced alarms can be raised to Civil Protection agencies.

I felt safer on this volcanic island than on other islands I have visited. If only such technological advances were easily available to alert the residents of potential eruptions, enabling their early evacuation from remoter volcanic islands worldwide, many disasters could be avoided.

References: I am most grateful to The Volcanological Centre on Vulcano for its staff’s most informative help. Such a centre also operates on Stromboli. Do visit www. [email protected]