Ocean Forms - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 57

two centimetres farther away from America, and the Pacific, which is
closing around the Ring of Fire. Then there are oceans that are nearly
dead, with the Mediterranean as the prime example. An ocean that is
so constricted can die more than once (as we shall see in the next
chapter), but its inal death will come a few tens of millions of years in
the future, when a mountain range has finally taken its place. Once
that happens, it will take hundreds of millions of years for the future
Mediterranean Mountains to be worn down, so that the sea can sweep
in once more.
We can now, more or less easily, wind the story back by something
approaching a billion years, with reasonable confidence over where
the continents and oceans used to be. Over that time there have been
a couple of supercontinents on Earth, when most of the Earth's con-
tinental crustal masses had joined together—and hence when there
was more or less unbroken ocean all around. Three hundred million
years ago, there was the supercontinent Pangaea, surrounded by the
mighty Panthalassa Ocean. The crustal fragments that came together,
long ago, to make up Pangaea had, some half a billion years earlier,
been combined in yet another supercontinent that geologists called
Rodinia, surrounded by an ocean to which the term Mirovia has been
given. Names, names, names—it is a very human trait to name objects,
large and small, even when those objects are constantly changing,
changing neighbours and partners, and moving on.
It can seem to be a never-ending process. It was first glimpsed by
James Hutton, a landowner and savant in late eighteenth-century
Scotland. Hutton was a fine product of the Scottish enlightenment,
but he left Edinburgh in 1747, likely because he got a girl pregnant.
This period of Hutton's life began with an indiscretion, then, but it did
not dampen his enthusiasm for all things scientific and modern. In
the time away from Scotland he completed his medical studies, honed
his skills in agriculture, and developed a new process for welding