C4 IV

~ FOR A MOMENT, HE THOUGHT that the Albireo had been flung bodily into the air. Then he decided that the great metal pillar had merely fallen over. Finally he realized that the ship was still erect, but the ground under it had just tried to leave.

Everyone in the group had become so used to the almost perpetual ground tremors that they had ceased to notice them; but this one demanded attention. Rowson, using language which suggested that his career might not have been completely free of adventure after all, flashed through the communication level on his way down to the power section. Schlossberg and Babineau followed, the medic pausing to ask Zaino if he were all right. The radioman merely nodded affirmatively; his attention was already back at his job. Burkett was speaking a good deal faster than before.

“Never mind if the sample isn’t lashed tight yet—if it falls off there’ll be plenty more. There isn’t time! Arnie, get in touch with Dr. Mardikian and Dr. Marini. Tell them that this volcano is explosive, that all estimates of what the flow may do are off until we can make more measures, and in any case the whole situation is unpredictable. Everyone should get back as soon as possible. Remember, we decided that those big craters Eileen checked were not meteor pits. I don’t know whether this thing will let go in the next hour, the next year, or at all. Maybe what’s happening now will act as a safety valve—but let’s get out. Ren, that flow is speeding up and getting higher, and the ash rain is getting a lot worse. Can you see to drive?”

She fell silent. Zaino, in spite of her orders, left his set long enough to leap to the nearest port for a look at the volcano.

He never regretted it.

Across the riven plain, whose cracks were now nearly hidden under the new ash, the black cone towered above the nearer elevations. It was visibly taller than it had been only a few hours before. The fountain from its top was thicker, now jetting straight up as though wind no longer meant a thing to the fiercely driven column of gas and dust. The darkness was not so complete; patches of red and yellow incandescence showed briefly in the pillar, and glowing sparks rather than black cinders rained back on the steep slopes. Far above, a ring of smoke rolled and spread about the column, forming an ever-broadening blanket of opaque cloud above a landscape which had never before been shaded from the sun. Streamers of lightning leaped between cloud and pillar, pillar and mountain, even cloud and ground. Any thunder there might have been was drowned in the howl of the escaping gas, a roar which seemed to combine every possible note from the shrillest possible whistle to a bass felt by the chest rather than heard by the ears. Rowson’s language had become inaudible almost before he had disappeared down the hatch.

For long moments the radioman watched the spreading cloud, and wondered whether the Albireo could escape being struck by the flickering, ceaseless lightning. Far above the widening ring of cloud the smoke fountain drove, spreading slowly in the thinning atmosphere and beyond it. Zaino had had enough space experience to tell at a glance whether a smoke or dust cloud was in air or not. This wasn’t, at least at the upper extremity....

And then, quite calmly, he turned back to his desk, aimed the antenna straight up, and called Eileen Harmon. She answered promptly.

The stratigrapher listened without interruption to his report and the order to return. She conferred briefly with her companion, replied “We’ll be back in twelve hours,” and signed off. And that was that.

Zaino settled back with a sign, and wondered whether it would be tactful to remind Rowson of his offer of a year’s pay.

All four vehicles were now homeward bound; all one had to worry about was whether any of them would make it. Hargedon and Burkett were fighting their way through an ever-increasing ash rain a scant two miles away—ash which not only cut visibility but threatened to block the way with drifts too deep to negotiate. The wind, now blowing fiercely toward the volcano, blasted the gritty stuff against their front window as though it would erode through; and the lava flow, moving far faster than the gentle ooze they had never quite measured, surged—and glowed—grimly behind.

A hundred miles or more to the east, the tractors containing Mardikian, Marini and their drivers headed southwest along the alternate route their maps had suggested; but Mardikian, some three hours in the lead, reported that he could see four other smoke columns in that general direction.

Mercury seemed to be entering a new phase. The maps might well be out of date.

Harmon and Trackman were having no trouble at the moment, but they would have to pass the great chasm. This had been shooting out daughter cracks when Zaino and Hargedon passed it hours before. No one could say what it might be like now, and no one was going out to make sure.

“We can see you!” Burkett’s voice came through suddenly. “Half a mile to go, and we’re way ahead of the flow.”

“But it’s coming?” Rowson asked tensely. He had returned from the power level at Zaino’s phoned report of success.

“It’s coming.”

“How fast? When will it get here? Do you know whether the ship can stand contact with it?”

“I don’t know the speed exactly. There may be two hours, maybe five or six. The ship can’t take it. Even the temperature measures I got were above the softening point of the alloys, and it’s hotter and much deeper now. Anyway, if the others aren’t back before the flow reaches the ship they won’t get through. The tractor wheels would char away, and I doubt that the bodies would float. You certainly can’t wade through the stuff in a spacesuit, either.”

“And you think there can’t be more than five or six hours before the flow arrives?”

“I’d say that was a very optimistic guess. I’ll stop and get a better speed estimate if you want, but won’t swear to it.”

Rowson thought for a moment.

“No,” he said finally, “don’t bother. Get back here as soon as you can. We need the tractor and human muscles more than we need even expert guesses.” He turned to the operator.

“Zaino, tell all the tractors there’ll be no answer from the ship for a while, because no one will be aboard. Then suit up and come outside.” He was gone.

Ten minutes later, six human beings and a tractor were assembled in the flame-lit near-darkness outside the ship. The cloud had spread to the horizon, and the sun was gone. Burkett and Hargedon had arrived, but Rowson wasted no time on congratulations.

“We have work to do. It will be easy enough to keep the lava from the ship, since there seems to be a foot or more of ash on the ground and a touch of main drive would push it into a ringwall around us; but that’s not the main problem. We have to keep it from reaching the chasm anywhere south of us, since that’s the way the others will be coming. If they’re cut off, they’re dead. It will be brute work. We’ll use the tractor any way we can think of. Unfortunately it has no plow attachment, and I can’t think of anything aboard which could be turned into one. You have shovels, such as they are. The ash is light, especially here, but there’s a mile and a half of dam to be built. I don’t see how it can possibly be done ... but it’s going to be.”

“Come on, Arnie! You’re young and strong,” came the voice of the mineralogist. “You should be able to lift as much of this stuff as I can. I understand you were lucky enough to get hold of Eileen—have you asked for the bonus yet?—but your work isn’t done.”

“It wasn’t luck,” Zaino retorted. Burkett, in spite of her voice, seemed much less of a schoolmistress when encased in a spacesuit and carrying a shovel, so he was able to talk back to her. “I was simply alert enough to make use of existing conditions, which I had to observe for myself in spite of all the scientists around. I’m charging the achievement to my regular salary. I saw—”

He stopped suddenly, both with tongue and shovel. Then, “Captain!”

“What is it?”

“The only reason we’re starting this wall here is to keep well ahead of the flow so we can work as long as possible, isn’t it?”

“Yes, I suppose so. I never thought of trying anywhere else. The valley would mean a much shorter dam, but if the flow isn’t through it by now it would be before we could get there—oh! Wait a minute!”

“Yes, sir. You can put the main switch anywhere in a D. C. circuit. Where are the seismology stores we never had to use?”

Four minutes later the tractor set out from the Albireo , carrying Rowson and Zaino. Six minutes after that it stopped at the base of the ash cone which formed the north side of the valley from which the lava was coming. They parked a quarter of the way around the cone’s base from the emerging flood and started to climb on foot, both carrying burdens.

Forty-seven minutes later they returned empty-handed to the vehicle, to find that it had been engulfed by the spreading liquid.

With noticeable haste they floundered through the loose ash a few yards above the base until they had outdistanced the glowing menace, descended and started back across the plain to where they knew the ship to be, though she was invisible through the falling detritus. Once they had to detour around a crack. Once they encountered one which widened toward the chasm on their right, and they knew a detour would be impossible. Leaping it seemed impossible, too, but they did it. Thirty seconds after this, forty minutes after finding the tractor destroyed, the landscape was bathed in a magnesium-white glare as the two one-and-a-half kiloton charges planted just inside the crater rim let go.

“Should we go back and see if it worked?” asked Zaino.

“What’s the use? The only other charges we had were in the tractor. Thank goodness they were nuclear instead of H. E. If it didn’t work we’d have more trouble to get back than we’re having now.”

“If it didn’t work, is there any point in going back?”

“Stop quibbling and keep walking. Dr. Burkett, are you listening?”

“Yes, Captain.”

“We’re fresh out of tractors, but if you want to try it on foot you might start a set of flow measures on the lava. Arnie wants to know whether our landslide slid properly.”

However, the two were able to tell for themselves before getting back to the Albireo .

The flow didn’t stop all at once, of course; but with the valley feeding it blocked off by a pile of volcanic ash four hundred feet high on one side, nearly fifty on the other and more than a quarter of a mile long, its enthusiasm quickly subsided. It was thin, fluid stuff, as Burkett had noted; but as it spread it cooled, and as it cooled it thickened.

Six hours after the blast it had stopped with its nearest lobe almost a mile from the ship, less than two feet thick at the edge.

When Mardikian’s tractor arrived, Burkett was happily trying to analyze samples of the flow, and less happily speculating on how long it would be before the entire area would be blown off the planet. When Marini’s and Harmon’s vehicles arrived, almost together, the specimens had been loaded and everything stowed for acceleration. Sixty seconds after the last person was aboard, the Albireo left Mercury’s surface at two gravities.

The haste, it turned out, wasn’t really necessary. She had been in parking orbit nearly forty-five hours before the first of the giant volcanoes reached its climax, and the one beside their former site was not the first. It was the fourth.

“And that seems to be that,” said Camille Burkett rather tritely as they drifted a hundred miles above the little world’s surface. “Just a belt of white-hot calderas all around the planet. Pretty, if you like symmetry.”

“I like being able to see it from this distance,” replied Zaino, floating weightless beside her. “By the way, how much bonus should I ask for getting that idea of putting the seismic charges to use after all?”

“I wouldn’t mention it. Any one of us might have thought of that. We all knew about them.”

“Anyone might have. Let’s speculate on how long it would have been before anyone did .”

“It’s still not like the other idea, which involved your own specialty. I still don’t see what made you suppose that the gas pillar from the volcano would be heavily charged enough to reflect your radio beam. How did that idea strike you?”

Zaino thought back, and smiled a little as the picture of lightning blazing around pillar, cloud and mountain rose before his eyes.

“You’re not quite right,” he said. “I was worried about it for a while, but it didn’t actually strike me.”

It fell rather flat; Camille Burkett, Ph.D., had to have it explained to her.