The First Ice Age on Earth

A clear autumn night on the northern shore of Lake Huron, on smooth grey rock streaked with pink, with small pines growing from the cracks. The rocks underfoot are more than two billion years old, and they hold the story of the first time the Earth grew cold. So we drift back, past the dinosaurs and far beyond them, to a bare world with no plants, a softer Sun, and air no one could breathe.

Along the way, thin green-brown mats of microbes breathing out the first oxygen, a fine rain of rust settling on a deep sea floor, a warm blanket of methane slowly thinning, glaciers moving like honey on a cold morning, icebergs letting their stones fall one by one into still mud, lakes keeping a diary of pale summers and dark winters, and the geologist Arthur Coleman kneeling by a road cut in 1907, reading an ice age in a single pebble. Then the gentle question nobody has settled: did the ice reach almost to the equator, and was the whole world briefly white?

The ending, given away now: the volcanoes slowly warm the world again, the air grows sweet, and we drift forward to the lakeshore, breathing air those microbes made. Far down in the stone, a pebble rests among its quiet stripes, as it has for two billion years.

The first minute

Let the day come to an end now. You have done what there was to do. Whatever is left can wait until morning. It will keep. For now, there is only the bed, and the dark, and the long, slow hours ahead. Let your shoulders settle. Let your jaw go soft. Let your hands lie still, and heavy, and warm. Let your breathing slow down. Slow, and even, and in no hurry at all. Tonight we are going to the shore of a great lake in Canada. And from there, we are going further back than almost any story goes.…

Why this one works at night

Everything in it moves at the speed of ice. Snow that does not quite melt, a glacier that creeps a few steps a day, a stone sinking through cold water, a stripe of mud laid down once a year. There are no animals, no people for most of it, nothing to watch for, only light, water and stone going about their slow business. The scale is so large that it stops being a number and becomes a feeling, like a hill seen through mist. And the one open question, a white world or a world with ice at its edges, is offered as two pictures to hold side by side, not a puzzle to solve.

“…Thin stripes of mud, laid down one after another, with stones resting among them—”

The kind of sentence people fall asleep during