Feeds:
Posts
Comments

Posts Tagged ‘moons’

Volcanoes A Beginners Guide by Rosaly LopesVolcanoes: A Beginner’s Guide, Rosaly Lopes (Oneworld 2010)

My first introduction to volcanoes was fictional: Willard Price’s Volcano Adventure (1956), which stands out in his Adventure series because it centres on something inanimate, not on animals like lions or gorillas or elephants. This book by the NASA scientist Rosaly Lopes is factual but equally enjoyable. And some of it would fit well into Volcano Adventure anyway:

[V]olcanoes come with different sizes, shapes and temperaments. It is fascinating to study what causes these differences and understand that, while generalizations are possible, each volcano has its distinct quirks, just like people. We could also compare volcanoes to cats: with few exceptions, they spend most of their lives asleep. (ch. 1, “What are volcanoes?”, pg. 1)

When a volcano wakes, look out. They’ve slain cities, devastated eco-systems and shaped landscapes. They’re also shaped cultures. Like a thunderstorm or earthquake, an erupting volcano raises a big question in the minds of human observers: What caused something so powerful and impressive? Our explanations began with myth and moved to science. And they moved a long time ago: the ancient philosopher Anaxagoras “proposed that volcanic eruptions were caused by great winds within the Earth, blowing through narrow passages” (pg. 5) and becoming hot by friction. Two-and-a-half millennia later, scientists are plotting “silica (SiO2) content” against “alkali content” as they classify “different volcanic rocks” (ch. 2, “How volcanoes erupt”, pg. 15).

But Anaxogaras’ principles are still at work: seek the explanation in mindless mechanism, not in supernatural mind. Classification is another essential part of science. In vulcanology, the scientific study of volcanoes, magmas are classified and so are eruptions, from subdued to spectacular: Icelandic and Hawaiian are on the subdued side, Peléean, Plinian and Ultraplinian on the spectacular, with Strombolian and Vulcanian in between. Some eruptions are easy to understand and investigate. Some are difficult. Volcanoes can be as simple or complicated as their names. Compare Laki, on Iceland, with Eyjafjallajökull, also on Iceland.

Laki is an example of an eco-slayer:

Although the eruption did not kill anyone directly, its consequences were disastrous for farmland, animals and humans alike: clouds of hydrofluoric acid and sulphur dioxide compounds caused the deaths of over half of Iceland’s livestock and, ultimately, the deaths – mostly from starvation – of about 9,000 people, a third of the population. The climatic effects of the eruption were felt elsewhere in Europe; the winter of 1783-4 as noted as being particularly cold. (ch. 3, “Hawaiian and Icelandic eruptions: fire fountains and lava lakes”, pg. 31)

Lopes goes on to look at city-slayers like Mount Pelée and Vesuvius, but they can be less harmful to the environment. A spectacular eruption can be over quickly and release relatively little gas and ash into the atmosphere. And death-dealing is only half the story: volcanoes also give life, because they enrich the soil. They enrich experience too, not just with eruptions but with other phenomena associated with vulcanism: geysers, thermal springs, mudpools and so on.

And that’s just the planet Earth. Lopes also discusses the rest of the solar system, from Mercury, Venus and Mars to the moons of gas giants like Jupiter and Saturn. The rocky planets have volcanoes more or less like those on earth, but the moons of the gas giants offer an apparent paradox: cryovolcanoes, or “cold volcanoes”, which erupt ice and water, not superheated lava. On Neptune’s moon Triton, whose surface is an “extremely cold” -235ºC, cryovulcanism may even involve frozen nitrogen. The hypothesis is that under certain conditions, it’s heated by sunlight, turns into a gas and “explodes” in the “near-vacuum of Triton’s environment” (ch. 11, “The exotic volcanoes of the outer solar system”, pg. 138).

Hot or cold, big or small, on the earth or off it, volcanoes are fascinating things and this is an excellent introduction to what they do and why they do it.

Advertisements

Read Full Post »