This rock is called the Campanian Ignimbrite. Its origin was a
catastrophe that happened 35,000 years ago: a gigantic volcanic
explosion threw out at least 100 cubic kilometres of pumice and ash. The
evidence still covers an area of more than 30,000 square kilometres
around the Bay of Naples, extending from Roccamonfina in the north to
Salerno in the south. The violence of this eruption would make the event
that buried Pompeii seem like a small afterthought. An explosion of
steam and gluey lava blew out a great hole in the earth at the edge of
the Tyrrhenian Seanot so much a bite out of Italy's profile as a huge
punch. A vast cloud of incandescent material buoyed up with gas flowed
like a fiery tidal wave across the limestone terrain. Lumps of volcanic
rock were carried along willy-nilly in the mayhem: destruction of
vegetation was complete. When the cloud settled, in many places it was
hot enough to fuse solid: the wispy remains of volcanic fragments
testify to this welding.* There were almost certainly Palaeolithic human
witnesses to this destruction, who must have thought the gods had gone
berserk. The legacy of the earth's ferocity is this apparently mundane
rock that looks like cake. The angular fragments of rock within can now
be seen for what they arepieces of a destroyed volcano. It is ironic
that this destruction has now been reversed into constructing buildings
that are safe as houses. Naturally, nothing is safe in this uncertain
world. Looking down from the limestone hills you can imagine the hot,
devastating clouds settling over where limoncello is now brewed and
pizzas are spun, dumping down on the low ground as a thick, lethal
blanket. These kinds of rocks were deposited from pyroclastic surges.
Another eruption about 23,000 years later was marginally less
devastating and did not spread so widelyit produced a different deposit
known as the Tufo Galliano Napoletano, the Neapolitan yellow tuff.
Rather than the colour of cake, it is the colour of Dijon mustard. Once
you can recognize it, you spot blocks of it in many walls and buildings
around Naples itselfit is almost reminiscent of the London stock
bricks that make the Georgian parts of the English capital so appealing.
It is there in the walls of Roman remains. Most experts believe that the
volcanoes that remain to this day in the Campi Flegrei are aligned
around the edge of the massive hole, or caldera, left behind as the
legacy of this second huge eruption. The Bay of Naples itself hides most
of it. It may yet blow again.
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