Some thoughts from a geologist on the impact of the latest volcanic eruption on Iceland.
Iceland is entirely built of volcanic material. It is located on the Mid-Atlantic Ridge, a plate boundary that is pulling apart, allowing new crust to form. Unlike most of the ridge, Iceland is above sea level and represents a "hot spot" along the ridge where there is exceptional activity.
We have known about Iceland's volcanoes for several centuries but only in the last 50 years have we understood the underlying plate tectonic mechanism. Iceland's volcanoes have been studied in much detail and there is good historical evidence for the frequency of eruptions, etc.
Volcanic ash is composed of very fine particles produced by violent eruptions within the volcano's vent. Much of this ash is derived from basalt or andesite lava and can be very finely crystalline. Sometimes the lava can cool so quickly it does not crystallize at all but becomes a glass (the mineral and semi-precious stone called obsidian). This glass component would appear to be one cause of mechanical degradation within machinery such as jet engines.
Because the eruptions eject vast amounts of ash directly into the upper atmosphere, the ash becomes subject to wind currents. In the upper atmosphere the jet stream, which flows from west to east, carries the ash in a general eastward direction. In summer, the northern jet stream migrates further north, which may have important ramifications for the months ahead should the volcano continue to erupt.
There is no easy way to determine when the volcano will cease its current activity. It will dissipate its internal pent up energy, so we can expect a general slowing down of activity. Days, weeks or months? No-one can be really sure but the chances are that ash content should fall to a manageable level sooner rather than later.
Can mankind do anything about this situation - why aren't we able to control this problem? Plate tectonic activities - earthquakes, volcanic eruptions, tsunamis - are the most powerful forces on earth. There is nothing we can do to prevent them and there is no reason why we would think that we could stop or control them. We can't even predict them with any certainty.
The situation many people find themselves in today is difficult, to say the least. The problem is, we have been lulled into a sense of well-being and a belief that somehow we can be in control of Nature. Nowhere is this belief more pronounced than in the debate on anthropogenic global warming, a creed that is universally adopted by politicians and most of the media. It is therefore no wonder that so many lay people are taken in by the concept that we should not be hindered in our every day life by the machinations of Mother Nature.
Recently I read that scientists want to create a new geologic period. The Holocene (a.k.a. a time period considered to be "Recent") should now be relegated to geologic history as we are now in the "Anthropocene" Period, a time when Homo sapiens dominates the planet.
Only problem is, we don't dominate the planet. We barely influence a very small part of it.
Finally, I noticed that one BBC article on the volcanic ash story refers to some people who predicted rotten vegetables and flowers stuck in East Africa as "experts". I was so pleased to see that geologists are not referred to as "experts". Some of us may be experts in our particular field, but we remain, first and foremost, geologists.