His listeners stared at the little inflatable globe. By this time they were over Patagonia. The geologist answered their questions, pointing out features on the globe as he did. This kind of thing had happened before, he told them, and more than once. West Antarctica had been ocean, dry land, or ice sheet, many times in the millions of years since tectonic movement had deposited that continent in that position. And there appeared to be several unstable points in the long-term temperature changes — “instability triggers,” he called them, causing massive changes in a matter of years. “This climatological stuff is practically instantaneous as far as geologists are concerned. Like, there’s good evidence in the Greenland ice sheet that one time we went from glacial to interglacial in three years.” The geologist shook his head.

“And these ice sheet breakups?” Fort asked.

“Well, we think they might go typically in a couple hundred years, which is still very fast, mind you. A trigger event. But this time the volcano eruption makes it much worse. Hey look, there’s the Banana Belt.”

He pointed down, and across Drake Strait they saw a narrow icy mountainous peninsula, pointing in the same direction as the coccyx of Tierra del Fuego.

The pilot banked to the right, then more gently to the left, beginning a wide lazy turn. Below them as they stared down was the familiar image of Antarctica as seen in satellite photos, but everything was now brilliantly colored and articulated: the cobalt blue of the ocean, the daisy chain of cyclonic cloud systems spinning away to the north, the textured sheen of the sun on the water, the great gleaming mass of the ice, and the flotillas of tiny icebergs, so white in the blue.

But the familiar Q shape of the continent was now strangely mottled in the area behind the comma of the Antarctic peninsula, with gaping blue-black cracks in the white. And the Ross Sea was even more fractured, by long ocean-blue fjords, and a radial pattern of turquoise-blue cracks; and offshore from the Ross Sea, floating up toward the South Pacific, were some tabular icebergs that were like pieces of the continent itself, sailing away. The biggest one looked to be about the same size as New Zealand’s South Island, or even bigger.

After they had pointed out the biggest tabular bergs to each other, and the various features of the broken and reduced western ice sheet (the geologist indicated where he thought the volcano under the ice was, but it looked no different from the rest of the sheet), they simply sat in their seats and watched.

“That’s the Ronne ice shelf, there,” the geologist said after a while, “and the Weddell Sea. Yeah, there’s some slippage down into it too…. Up there’s where McMurdo used to be, on the far side of the Ross ice shelf. Ice was pushed across the bay and ran up over the settlement.”

The pilot started a second lap around the continent.

Fort said, “Now say again what effect this will have?”

“Well, theoretical models have world sea levels rising about six meters.”

“Six meters!”

“Well, it will take a few years for the full rise, but it’s definitely started. This catastrophic break will raise sea levels about two or three meters, in a matter of weeks. What’s left of the sheet will be afloat in a matter of months, or a few years at most, and that will add another three meters.”

“How could it raise the whole ocean that much?”

“It’s a lot of ice.”

“It can’t be that much ice!”

“Yes it can. That’s most of the fresh water in the world, right down there under us. Just be thankful the East Antarctic ice sheet is nice and stable. If it were to slide off, sea levels would rise sixty meters.”

“Six meters is plenty,” Fort said.

They finished another lap. The pilot said, “We should be getting back.”

“That’s it for every beach in the world,” Fort said, pulling his face back from the window. Then: “I guess we’d better go get our stuff.”

When the Second Martian revolution began, Nadia was in the upper canyon of Shalbatana Vallis, north of Marineris. In a sense one could say that she started it.

She had left South Fossa temporarily to oversee the Shalbatana closure, which was similar to those over Nirgal Vallis and the east Hellas valleys: a long tent roof over a temperate ecology, with a stream running down the canyon floor, in this case supplied by pumping from the Lewis aquifer, 170 kilometers to the south. Shalbatana was a long series of lazy S’s, so that the valley floor looked very picturesque, but the construction of the roof had been complicated.

Nevertheless Nadia had directed the project with only one small part of her attention, the rest being focused on the cascading developments on Earth. She was in daily communication with her group in South Fossa, and with Art and Nirgal in Burroughs, and they kept her informed of all the latest news. She was particularly interested in the activities of the World Court, which was trying to establish itself as an arbitrator in the growing conflict of the Su-barashii metanats and the Group of Eleven against Praxis, Switzerland, and the developing China-India alliance — trying to function, as Art had put it, “as a sort of world court.” That effort had looked doomed when the fundamentalist riots began and the metanats prepared to defend themselves; and Nadia had concluded unhappily that things on Earth were about to spiral down into chaos again.

But all these crises were immediately cast into insignificance when Sax called to tell her of the collapse of the West Antarctic ice sheet. She had taken his call at her desk in one of the construction trailers, and now she stared at his little face on the screen. “What do you mean, collapsed?”

“It’s lifted off the bedrock. There’s a volcano erupting. It’s being broken up by ocean currents.”

The video image he was sending cut to Punta Arena, a Chilean harbor town with its docks gone and its streets awash; then it cut again to Port Elizabeth in Azania, where the situation was much the same.

“How fast is it?” Nadia said. “Is it a tidal wave?”

“No. More like a very high tide. That will never go away.”

“So enough time to evacuate,” Nadia said, “but not enough time to build anything. And you say six meters!”

“But only over the next few … no one is sure how long. I’ve seen estimates that as much as a quarter of the Terran population will be — affected.”

“I believe it. Oh, Sax …”

A worldwide stampede to higher ground. Nadia stared at the screen, feeling stunned as the scale of the catastrophe became clearer to her. Coastal cities would be awash. Six meters! She found it very hard to imagine that any possible ice mass could be so large as to raise the sea level of all Earth’s oceans by even as much as one meter — but six! It was shocking proof, if one needed it, that the Earth was not so big after all. Or else that the West Antarctic ice sheet was huge. Well, it had covered about a third of a continent, and was, the reports said, some three kilometers thick. That was a lot of ice. Sax was saying something about the East Antarctic ice sheet, which apparently was not threatened. She shook her head to clear it of this nattering, concentrated on the news. Bangladesh would have to be entirely evacuated; that was three hundred million people, not to mention the other coastal cities of India, like Calcutta, Madras, Bombay. Then London, Copenhagen, Istanbul, Amsterdam, New York, Los Angeles, New Orleans, Miami, Rio, Buenos Aires, Sydney, Melbourne, Singapore, Hong Kong, Manila, Djakarta, Tokyo … and those were only the big ones. A lot of people lived on the coast, in a world already severely stressed by overpopulation and declining resources. And now all kinds of basic necessities were being drowned by salt water.

“Sax,” she said, “we should be helping them. Not just…” . “There is not that much we can do. And we can do that best if we’re free. First one, then the other.”