EVER AGAIN - Snowball Earth - page 108

So India crashed into Asia, and the land began to rise. First the crust of Asia squeezed around the
sides of the thrusting arriviste. Then, as India wedged itself like a chisel further beneath Asia, the sur-
face crust crumpled and folded into a range of mountains more than two thousand miles long. These
were the beginnings of the Himalayas. And the land around the mountains was forced up into a vast
plateau, the “roof of the world”, whose average height is greater than the highest mountain in Amer-
ica. India is still pushing. The Himalayas grow by nearly half an inch a year, and Everest and its kin
would be even taller if their fresh young rocks weren't eroding away as they rose.
Meanwhile, partway round the world, Africa was aggressively reacquainting itself with its old
Pangaean neighbour, Europe. The first part to hit was a peninsula, sticking out from the northern part
of the African plate and bearing what is now Italy and Greece and the countries of former Yugoslavia.
This collision threw up the beginning of the Alps. Spain crammed into France, and henceforth there
were Pyrenees. And though Africa and Eurasia may seem as if they are only joined at their Arabian
hip, the Mediterranean is slowly closing. When Africa itself collides with the European continent, a
mighty new range of mountains will be born.
Arabia is now shoving into Iran. Europe and Asia have never been parted since Pangaea, and Aus-
tralia is heading northwards to join in. In a few tens of millions of years, Australia's left shoulder will
probably catch on the southernmost islands of Southeast Asia. It will twist and jerk upwards, to slam
into Borneo and the southern parts of China.
Predicting the future of continental movements is an inexact science. But supercontinents come
and go over time, and most of the world's landmasses are already crammed into this one gigantic
block. Only the Americas and Antarctica remain aloof. As the Atlantic Ocean widens, America is
moving steadily further from Europe, and the most dramatic drift within the North American contin-
ent is the one taking Los Angeles and Baja northwards. (In about 10 million years, L.A. will pass San
Francisco, and by 60 million years from now, it will be heading down a trench into the Earth's interior,
just south of Alaska.) But some researchers predict that the Americas, too, will be reunited with the
rest of the world's landmasses. According to one attempt at constructing the future, over the next few
hundred million years the Atlantic will begin to close again, bringing North and South America back
into the fold, and Antarctica will head north to join India. 5
If so, in 250 million years, the new Pangaea could form. Then it would need to survive intact for
another hundred million years or so, while a plume of hot mantle built up beneath. It would shift to the
equator in a geological eye blink, just a million years or so, to right the balance of the spinning world;
it would break up, and scatter its pieces around the equator and tropics. And then the ice would return.
Gradually the frozen polar oceans begin to reach out with tentative feelers of ice. Finding nothing
to stop them, they continue their spread. The whiteness advances like a disease that gradually covers
the planet's blue surface. The oceans turn greasy, first, with smashed ice crystals. Then the pancakes
of ice are back, and the frost flowers, and the transparent young coating of sea ice that bends with the
swell. The ice thickens, and spreads, and thickens some more. By the time it reaches the tropics, it's
unstoppable, and in just a few centuries it goes all the way. Global temperatures plummet; rain stops;
clouds no longer form. Wisps of ice ripped from the frozen ocean are spread by the wind until they
begin to build up on the world's highest mountains. Slowly, steadily, the ice forms glaciers that spill
down on to the lowlands. And then the white-out is complete.
W HAT WILL our descendants do? Perhaps they will be so unimaginably advanced that they'll be able
to prevent a Snowball. They might be routinely tapping additional energy from the sun, or stopping