Volcanoes
A volcanic eruption is a fierce but short-lived event. Most eruptions have a duration from one week to three years. Although we know of about 1000 land volcanoes that have had less than 10,000 eruptions in historical time, those eruptions have usually been middle-sized (55%) or small and non-explosive (25%) and more seldom large (18%) or very large (2%). What makes volcanoes important as natural hazards is the fact that even small eruptions have large effects.
Volcanoes as suppliers of building material
A small eruption has strength 1 (VEI:1) on the 8-grade volcanic eruptions scale, and releases less than 1 million m3 of solid particles, which is less than 2 million tons of rock. By human reckoning this is still a substantial amount, it is more than all the concrete used to build the bridge and tunnel link between Denmark and Sweden, for instance. A VEI:2 eruption releases ten times more solid material. Any constructor understands that volcanoes are a huge source of bulk material—this is well known in Japan and Iceland.
The world’s best thermal insulation material, pumice, is only formed during powerful volcanic eruptions. Some volcanoes—though not all as many believe—expel lava that forms basalt. The Romans used basalt to build their roads, many of which are still in excellent shape today. Other volcanoes expel rock particles of all sizes, from clay to house-size boulders. After heavy rains these particles will move as a sludge or porridge down the volcano slopes; these rivers of hot or cold rock sludge are called lahars and should not be confused with lava flows. Lahars rarely reach more than 50-100 km from the crater, though some have been known to reach 250 km. Lahars are natural suppliers of bulk material, if their location is known crushing and sorting plants can make quick work.
Sulphur production
Crater lakes form on some volcanoes. If the volcano is active the lake is not filled with water but newly produced sulphuric acid, with large amounts of small particles of pure sulphur at the bottom of the lake. When the volcano erupts the acid in the lake, sometimes 20 million tons, is emptied with devastating ecological consequences to the water systems. Twenty years ago we suggested that Indonesia should start sulphur extraction and acid plants in some of the country’s many crater lakes. At that time 20 million USD could have been saved annually from not having to import sulphur. We know of many places in low-income countries (that also import sulphur) where small chemical plants could be started. At the same time the ecological effects of future eruptions would be lessened.
Ecological impact
The most important ecological aspect of volcanoes is the volcanic gas, which also affect our climate. In one year Etna vents more than 1 million tons of sulphur dioxide (severely corroding the bridge to be built over the strait of Messina), and more than 10 million tons of carbon dioxide. During eruption the amounts are ten times greater. Environmentalists seldom mention that volcanoes vent gas not just during their active period but during millions of years. Thus the emissions cannot be calculated by taking the number of active volcanoes (1000-1500) multiplied by the average amount of carbon dioxide vented. There are tens of thousands of dormant volcanoes that will continue venting carbon dioxide until they become inactive, which takes 10-12 million years.
Energy and chemical production
Many volcanoes are located in low-income countries. They produce enormous amounts of energy but with few exceptions their geothermal energy has not been exploited. At the same time volcanoes are the world's largest chemical factories. Etna vents 100,000 tons of hydrogen sulphide each year, along with 110,000 tons of hydrochloric acid, 5000 tons of hydrogen fluoride, 27 tons of mercury, and 10 tons of cadmium. We believe we might be able to supply some project ideas for innovative industry people with environmental interests, some relating to future trade in emission rights.
Volcanic ash and air traffic
Millions of air passengers pass over explosive volcanoes every day. They need not be afraid, as pilots know what should be done if something happens. But more attention should be given to the effects of large volcanic eruptions. Using Iceland as an example, we know that there is a large eruption there two times every hundred years. In certain wind directions the next large eruption would paralyse air traffic in northern Europe. No planes will crash, but flights will have to be cancelled for several days on account of volcanic ash, which will require better planning. During the Pinatubo eruption in the Philippines ash from the volcano destroyed jet engines of more than ten aircraft. None of these planes were closer than 1000 km to the volcano, and they could land safely, but engines costing a few hundred million dollars had to be replaced. We have experience of eruptions and our TRITON database to help us establish future risks of interest to your business.