Fire, earth, air and water

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A long exposure photograph shows lava spilling down from the crater of Mount Sinabung volcano on March 14. — File photo

HOW well do we really know the treasures of our nearest neighbour Indonesia? As a former guru besar of an international school in Sarawak, it was my great pleasure to advise my Indonesian students on their entry to universities worldwide. Subsequently many have kept in contact with me and especially one from Balikpapan. He was the very person who first alerted me to the magnificent national parks in Indonesia.

Three years ago, my son and my daughter-in-law ventured beyond Surabaya, East Java, on a pony trek across a volcanic ash desert to climb Gunung Bromo at 2,329 metres. Years before he had climbed Fujiyama in Japan, but he reckons that the spectacular volcanic scenery in the Bromo-Tenggar-Semeru National Park is second to none in the world.

Indonesia, with all of its islands, is located on what geologists refer to as the Pacific Ring of Fire. More precisely, all of these islands are sited on the Sunda Arc. Here the edges of the Eurasian and Indo-Australasian tectonic plates collide. In their convergence, over millions of years, the folded mountains of the Barisan Ranges in Sumatra and Java and the Penrissen Range on the Sarawak-Kalimantan border have thus been uplifted from former sea deposits.

At this plate margin, where the more dense Indo-Australian oceanic plate dives under the less dense Eurasian continental plate, heat is produced, in the subduction zone, by the friction of the plates grinding against each other. This heat, in turn, melts the surrounding rock creating magma, which rises through the mountain ranges to the surface bursting out in emissions of volcanic ash and lava outpourings.

Volcanic eruptions are not unusual in Indonesia, with its 130 or so active volcanoes. In recent years, and especially since Aug 29, 2010, much publicity has been given to the volcanic eruptions of Gunung Sinabung (2,460 metres high) on Sumatra. This volcano had lain dormant for 410 years.

Just beyond the southern boundary of Gunung Leuser National Park and northwest of the crater-lake Toba, it lies almost due west of Kuala Lumpur across the Straits of Malacca. Lake Toba is the largest crater-lake in the world. It erupted 73,500 years ago and ejected millions of tonnes of volcanic ash into the atmosphere to block out the sun’s rays resulting in a rapid cooling of temperature in the northern hemisphere.

This may have led to the last Ice Age. Certainly it was the greatest volcanic eruption over the last million years. When most of the magma had been emitted from the cauldron chamber, the vent area of the volcano collapsed into the void beneath to create a caldera – Lake Toba.

Mount Sinabung spews hot lava and volcanic ash on Oct 14, 2014. — File photo

Technically, Sinabung is classified as a strato-volcano composed of alternating layers of ash and lava creating a typical volcanic cone shape with smooth concave sides running up to a central peak, not dissimilar from Fujiyama.

At times in its geological history there have been explosive events with millions of tonnes of tiny fragments of molten lava blasted high into the atmosphere before raining down to create deep layers of ash. Such explosive eruptions have been rapidly followed by outpourings of red hot liquid lava, creating another layer overlying the ash deposits.

The lava layers on Gunung Sinabung are composed of two types of volcanic material, andesite and dacite – the former named after the Andean volcanoes in South America and the latter after an ancient Roman province of Dacia, now comprising Romania and Moldavia. Andesite has 52 to 63 per cent silica (SiO2) content and dacite is composed of 63 to 69 per cent silica.

Sinabung, in 2010, ejected volcanic ash to a height of 1.7km above its summit and lava flowed from its vent forcing the evacuation of thousands of people. Such eruptions continued until January 2014. In December 2013, the ash plumes rose to 7km, forcing Medan airport to close. Already, this year, ash plumes to a height of 3.7km have been recorded with the fallout of ash in a south easterly direction. With these eruptions, sadly, human lives have been lost: those of villagers, spectators and geologists, many of whom were asphyxiated by the dust clouds.

Ancient Greek philosophers often discussed the four elements of life: fire, air, earth and water. These four elements can be applied to Gunung Sinabung’s recent eruptions and to our own lives. You may well ask, “Where does water come into volcanic eruptions?”

Volcanic activity ejects vast quantities of hot air containing water vapour into the atmosphere as well as volcanic dust to very great heights. The minute particles of ash cool and water vapour droplets are attracted to these condensation nuclei, creating clouds of considerable vertical heights. The water droplets collide with each other via convection currents in the rising hot air above a volcano’s vent and, in doing so, build up static electricity at the top of the clouds.

This area of the cloud is positively charged but the base of the cloud mass collects negative charges. The jump between positively and negatively charged ions creates sparks. Such electrical discharges produce lightning to create more than a million volts of electricity. If only we had the technical knowledge to tap and store such energy and transmit it for everyday usage.

One of the world’s largest volcanic eruptions, that of Krakatoa – east of Java – in 1883 emitted so much heat and water vapour that lightning in the shape of pine trees emblazoned the skies there whilst thunder more than just rolled and the rain poured down. That was truly a period of night-time firework displays.

The volcanic ash carried around the world by high altitude winds affected climates worldwide for many years in the late 19th century. The havoc caused by torrential rain falling on volcanic dust creates massive mud or ash flows, as witnessed when Vesuvius erupted in AD 79 in Italy. There, the Roman settlements of Pompeii and Herculaneum were literally buried in ash and mud. Much the same can be said of many villages on the lower slopes of Gunung Sinabung.

The old adage, that lightning never strikes twice in the same place, can be thrown out of the window by the residents of the villages of Tiga Paneur and Payung beneath the recent eruptions from one of Sinabung’s four summits. Those villagers have experienced nightly the greatest fireworks display on earth in lightning illuminating the whole sky.

Yet, every cloud has a silver lining, especially for farmers. It is proven that lightning is a natural soil fertiliser showering down on our soils 100 million tonnes of nitrogen each year. This, together with the eventual weathering of ash and lava flows, may explain the very intensive farming and high levels of production in most of Java and why the vineyards on the slopes of Vesuvius caught my eye.

Whilst volcanic eruptions cause terrible local havoc and disasters and inconvenience to travellers, their sheer beauty as landforms are sights to see. I have climbed extinct volcanic peaks in the UK and visited Mount Kenya, Kilimanjaro (East Africa) and Fujiyama in Japan but my greatest thrills have taken me to the crater of Vesuvius (Italy) and, later in life, to look down onto a crater lake on the island of Mayotte in the Indian Ocean. Volcanic ash has, however, overtaken me.

Five years ago on a flight from Kuala Lumpur to London the now infamous Icelandic volcano, Eyjafjallajokull, ejected so much ash into the atmosphere that my aeroplane was diverted for a two-hour stay at Charles de Gaulle Airport in Paris until the ash had been blown away over London.

At that time, I cursed volcanic eruptions but, as a geographer and geologist, I am totally fascinated as to where and when these releases of underground energy arrive at the surface of Planet Earth, for each volcanic outburst signals tectonic plate movements. I have yet to visit Stromboli north of the island of Sicily, in the Mediterranean Sea, the Icelandic volcanic landscapes and even, much nearer to Sarawak and Sabah, our neighbouring Indonesian active volcanoes.

A long exposure photograph taken before dawn on Oct 14, 2014 shows sparks of lightning, scorching lava flow and giant ash clouds released from the crater during the eruption of Mount Sinabung volcano. — File photo