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cubic kilometers of ash into the air in a great tree-like plume that towered
80 kilometers to the fringes of outer space. This immense plume blew away
to the northwest, covering much of what is now Malaysia with a smothering
layer of ash and sifting down as far away as central India to form an ash layer
that is 6 meters thick in places. It is estimated that for a decade afterward world
temperatures were as low as they were during the peak of the last ice age.
Volcanic explosions such as Mount Toba leave many traces behind, but
the ef ects of past tsunamis are more dii cult to detect. We do know that tsu-
namis happen all the time—24 of them have hit North America over the past
quarter of a millennium. And at least one tsunami has changed the course
of civilization. When the caldera of the Mediterranean island of Santorini
collapsed in about 1650 bce, it produced a wave 100 meters high that swept
away much of the thriving and highly advanced civilization of Crete, 150
kilometers to the south.
Many tsunamis of the distant past must have been even more violent,
though the further back one goes in time the more uncertain the evidence
becomes. It is generally agreed, however, that about 250,000 years ago an
immense tsunami hit the islands of Hawaii. The wave was so huge that it
deposited large rocks 250 meters above the sea level of that time.
What was the biological ef ect of these various disasters? Probably sur-
prisingly little. Small events, like the one I experienced of the island of Yap,
generally have little ef ect. The coral reefs near Yap that were damaged will
soon heal. Fresh coral growth quickly knits together the rubble from old
earthquakes and builds new living structures that reach toward the light.
Darwin's earthquake also had little ef ect on the non-human world. When
he picked himself up of the ground after the Chilean earthquake, Darwin
was struck by the fact that the forest around him seemed quite unperturbed.
Even the millions of mussels and other intertidal organisms that the Beagle 's
crew later found rotting above the high tide mark along the nearby coast
were soon replaced. There are always clouds of eager larvae swarming in that
cold, rich ocean, searching for empty places to settle down.
But what about the really big events? Surely the Toba catastrophe, for
example, must have had an ef ect on us and on other animals. Stanley
 
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