But Hans is shaking his head, a smile on his face. He gestures for the brandy flask again. “The point is, the lava shield of Olympus Mons is a single unit of rock—layered, admittedly, but essentially one big cap of basalt, placed on a slightly soft surface. Now by far the greatest part of the weight of this cap is near the center—the volcano’s peak, you know, still so far above us. So—the cap is a unit, a single piece of rock—and basalt has a certain flexibility to it, as all rock does. So the cap itself is somewhat flexible. Now the center of it sinks the farthest, being heaviest—and the outside edge of the shield, being part of a single flexible cap, bends upward.”
“Up twenty thousand feet?” Arthur demands. “You’re kidding!”
Hans shrugs. “You must remember that the volcano stands twenty-five kilometers above the surrounding plains. The volume of the volcano is one hundred times the volume of Earth’s largest volcano, Mauna Loa, and for three billion years at least it has been pressing down on this spot.”
“But it doesn’t make sense that the scarp would be so symmetrical if that was what happened,” Frances objected.
“On the contrary. In fact that is the really telling aspect of it. The outer edge of the lava shield is lifted up, okay? Higher and higher, until the flexibility of the basalt is exceeded. In other words, the shield is just so flexible and no more. At the point where the stress becomes too much, the rock sheers off, and the inner side of the break continues to rise, while what is beyond the break point subsides. So, the plains down below us are still part of the lava shield of Olympus Mons, but they are beyond the break point. And as the lava was everywhere approximately the same thickness, it gave way everywhere at about the same distance from the peak, giving us the roughly circular escarpment that we now climb!”
Hans waves a hand with an architect’s pride. Frances sniffs. Arthur says, “It’s hard to believe.” He taps the floor. “So the other half of this cave is underneath the talus wash down there?”
“Exactly.” Hans beams. “Though the other half was never a cave. This was probably a small, roughly circular layer of tuff, trapped in much harder basaltic lava. But when the shield broke and the escarpment was formed, the tuff deposit was cut in half, exposing its side to erosion. And a few eons later we have our cozy cave.”
“Hard to believe,” Arthur says again.
Roger sips from the flask and silently agrees with Arthur. It’s remarkable how difficult it is to transfer the areologist’s theories, in which mountains act like plastic or toothpaste, to the vast hard basalt reality underneath and above them. “It’s the amount of time necessary for these transformations that’s difficult to imagine,” he says aloud. “It must take . . .” He waves a hand.
“Billions of years,” Hans says. “We cannot properly imagine that amount of time. But we can see the sure signs of its passing.”
And in three centuries we can destroy those signs, Roger says silently. Or most of them. And make a park instead.
Above the cave the cliff face lies back a bit, and the smoothness of the Jasper Band is replaced by a jumbled, complicated slope of ice gullies, buttresses, and shallow horizontal slits that mimic their cave below. These steps, as they call them, are to be avoided like crevasses on level ground, as the overhanging roof of each is a serious obstacle. The ice gullies provide the best routes up, and it becomes a matter of navigating up what appears to be a vertical delta, like the tracing of a lightning bolt burned into the face and then frozen. Every morning as the sun hits the face there is an hour or so of severe ice and rockfall, and in the afternoons in the hour after the sun leaves the face there is another period of rockfall. There are some close calls and one morning Hannah is hit by a chunk of ice in the chest, bruising her badly. “The trick is to stay in the moat between the ice in the gully and the rock wall,” Marie says to Roger as they retreat down a dead-end couloir.
“Or to be where you want to be by the time the sun comes up,” Dougal adds. And on his advice to Eileen, they begin rising long before dawn to make the exposed parts of the climb. In the frigid dark a wristwatch alarm beeps. Roger twists in his bag, trying to turn it off; but it is his tent mate’s. With a groan he sits up, reaches over and switches on his stove. Soon the metal rings in the top of the cubical stove are glowing a friendly warm orange, heating the tent’s air and giving a little bit of light to see by. Eileen and Stephan are sitting in their bags, beating sleep away. Their hair is tousled, their faces lined, puffy, tired. It is 3:00 A.M. Eileen puts a pot of ice on the stove, dimming their light. She turns on a lamp to its lowest illumination, which is still enough to make Stephan groan. Roger digs in a food pouch for tea and dried milk. Breakfast is wonderfully warming, but suddenly he has to visit the cave’s convenient yet cold latrine. Boots on—the worst part of dressing. Like sticking one’s feet into ice blocks. Then out of the warm tent into the intense cold of the cave’s air. Through the dark to the latrine. The other tents glow dimly—time for another dawn assault on the upper slopes.
By the time Archimedes, the first dawn mirror, appears, they have been on the slopes above the cave for nearly an hour, climbing by the light of their helmet lamps. The mirror dawn is better; there is enough light to see well, and yet the rock and ice have not yet been warmed enough to start falls. Roger climbs the ice gullies using crampons; he enjoys using them, kicking into the plastic ice with the front points of the crampons, and adhering to the slopes as if glued to them. Below him Arthur keeps singing a song in tribute to his crampons: “Spiderman, Spiderman, Spiderman, Spidermannnnn.” But once above the fixed ropes, there is no extra breath for singing; the lead climbing is extremely difficult. Roger finds himself spread-eagled on one pitch, right foot spiked into the icefall, left foot digging into a niche the size of his toenail; left hand holding the shaft of the ice axe, which is firmly planted in the icefall above, and right hand laboriously turning the handle of an ice screw, which will serve as piton in this little couloir: And for a moment he realizes he is ten meters above the nearest belay, hanging there by three tiny points. And gasping for breath.
At the top of that pitch there is a small outcropping to rest on, and when Eileen pulls herself up the fixed rope she finds Roger and Arthur laid out over the rock in the morning sunlight like fish set out to dry. She surveys them as she catches her wind, gasping herself. “Time for oxygen,” she declares. In the midday radio call she tells the next teams up to bring oxygen bottles along with the tents and other equipment for the next camp.
With three camps established above the cave, which serves as a sort of base camp to return to from time to time, they are making fair progress. Each night only a few of them are in any given camp. They are forced to use oxygen for almost all of the climbing, and most of them sleep with a mask on, the regulator turned to its lowest setting. The work of setting up the high camps, which they try to do without oxygen, becomes exhausting and cold. When the camps are set and the day’s climbing is done, they spend the shadowed afternoons wheezing around the camps, drinking hot fluids and stamping their feet to keep them warm, waiting for the sunset radio call and the next day’s orders. At this point it’s a pleasure to leave the thinking to Eileen.
One afternoon climbing above the highest camp with Eileen, Roger stands facing out as he belays Eileen’s lead up a difficult pitch. Thunderheads like long-stemmed mushrooms march in lines blown to the northeast. Only the tops of the clouds are higher than they. It is late afternoon and the cliff face is a shadow. The cottony trunks of the thunderheads are dark, shadowed gray—then the thunderheads themselves bulge white and gleaming into the sunny sky above, actually casting some light back onto the cliff. Roger pulls the belay rope taut, looks up at Eileen. She is staring up her line of attack, which has become a crack in two walls meeting at ninety degrees. Her oxygen mask covers her mouth and nose. Roger tugs once—she looks down—he points out at the immense array of clouds. She nods, pulls her mask to one side. “Like ships!” she calls down. “Ships of the line!”