Geoscience Reference
In-Depth Information
Chapter 6
Volcanoes
The relentless motions of tectonic plates, the uplift and the erosion of mountain ranges, and
the evolution of living organisms are processes which can only be fully appreciated across
the deep time of geology. But some of the processes at work in our planet can manifest all
too suddenly, changing the landscape and destroying lives on a very human timescale: vol-
canoes. Superimpose a map of active volcanoes on a world map showing the boundaries of
the tectonic plates and their association is obvious. The ring of fire around the Pacific, for
example, is clearly associated with the plate boundaries. But where is the molten rock that
feeds them coming from? Why are volcanoes different from each other, with some produ-
cing gentle eruptions and regular trickles of molten lava, whilst others erupt in devastating
explosions? And why are some volcanoes, such as those of Hawaii, in the middle of the Pa-
cific, far from any obvious plate boundary?
History is littered with eyewitness accounts of volcanic eruptions and with explanations,
some of them mythological, some fanciful, and some surprisingly accurate. Among the bet-
ter accounts is that of Pliny the Younger, describing the eruption of Vesuvius in 79
AD
which
