“Keep close together,” Costas warned. “These things may last for hours but they barely light up the floor. We don’t know what to expect.”
As they rounded a bend in the passage, the acrid odour which had irritated their nostrils since surfacing suddenly became indescribably foul. A warm draught carried with it the sickly-sweet smell of decay, as if the dead of Atlantis were still putrefying in their sepulchre far below.
“Sulphur dioxide,” Costas announced, his nose crinkling slightly. “Unpleasant, but not toxic if we don’t stick around for too long. There must be an active vent nearby.”
As they continued upwards they saw where another lava tube had broken through, gushing its contents like spilled concrete over the tunnel floor. The lava was jagged and brittle but did not restrict their passage like the previous flow. The hole where it emerged was rent with a honeycomb of cracks and fissures, the source of the unholy wind that intensified with every step of their approach.
“These two lava tubes we’ve encountered are relatively recent,” Costas said. “They must have broken through since the flood, otherwise the priests would have had them cleaned out and the tunnel repaired.”
“There must have been similar eruptions during the time of Atlantis,” Katya said shakily. “This place is far more active than geologists ever suspected. We’re inside a time bomb.”
Jack had been fighting the pain, a pulverizing sensation that had grown as the numbing effect of the cold wore off. Now every breath was a vicious stab, every step an agonizing jolt that pushed him to the brink of collapse.
“You two go on. We must contact Seaquest as soon as possible. I’ll follow when I can.”
“Not a chance.” Costas had never seen his friend concede defeat, and knew Jack would force himself on until he dropped, whatever the odds. “I’ll carry you on my back if it comes to it.”
Jack marshalled his remaining strength and slowly, agonizingly, followed the other two over the lava, picking his way carefully across the jagged formations. Progress was easier as the sloping floor became a series of shallow steps. About twenty metres beyond the lava, the passageway curved south, the dimensions gradually losing their regularity as the walls gave way to the natural shapes of a volcanic fissure. As the tunnel constricted further, they began to climb single file, with Costas in the lead.
“I can see light ahead,” he announced. “This must be it.”
The elevation increased sharply and they soon found themselves scrambling on their hands and knees. As they approached the dim aura of light the algae made each step progressively more treacherous. Costas slithered over the final shelf and turned back to give Jack a hand.
They had come out beside a conduit some three metres wide by three metres deep, the sides smoothed by millennia of erosion. At the bottom was a shallow stream that seemed to plummet down a narrow canyon, the distant roar of water audible but their view completely obscured by a sheen of mist. To the right the conduit headed into the rock face with a glimmer of light beyond.
Costas peered at his console to check his altimeter.
“We calculated the height of the volcano before the flood at three hundred and fifty metres above sea level. We’re now one hundred and thirty-five metres above present sea level, only about eighty metres below the tip of the cone.”
Having penetrated the volcano on the north side, they were now facing due west, the shape of the passageways reflecting the incline of the upper slopes. Ahead of them the dark mouth of the tunnel seemed set to plunge back into the labyrinth, yet it could only be a short stretch before they reached open air.
“Be careful,” Costas said. “One wrong step and this chute will send us straight to hell.”
They had lost track of time since embarking in the DSRV from Seaquest the previous day. The jumble of rock was a twilight world of shadows and flickering shapes. As they negotiated a short flight of steps cut into the rock, the conduit became gloomier still, and they once again had to rely on the eerie glow from the lightsticks.
The tunnel followed the drift of the basalt, each successive layer clearly visible in the stratigraphy of the walls. The flow had undermined the gas-charged lava of the cone, the ash and cinders compressed like concrete with chunks of pumice and jagged scoriae embedded in the matrix. The higher they climbed, the more porous it became, with rainwater dripping through the clumps that protruded from the ceiling. The temperature was becoming noticeably warmer.
After about twenty metres the tunnel narrowed and funnelled the water flowing against them into a violent current. Jack stumbled sideways, his body suddenly convulsed with pain. Katya waded over to help him stay upright against the torrent which was now waist high. With agonizing slowness the two of them forced their way past the constriction while Costas forged ahead and disappeared into the veil of mist. As they staggered forward, the walls suddenly opened out again and the flow diminished to little more than a trickle. They rounded a corner and saw Costas standing motionless, his dripping form silhouetted against a background of opaque illumination.
“It’s a huge skylight,” he announced excitedly. “We must be just below the caldera.”
The opening far above was wide enough for faint daylight to reveal the awesome scale of the chamber in front of them. It was a vast rotunda, at least fifty metres across by fifty metres high, the walls rising to a circular aperture which framed the sky like a giant oculus. To Jack it was astonishingly reminiscent of the Pantheon in Rome, the ancient temple to all the gods, its soaring dome representing mastery over the heavens.
Even more breathtaking was the apparition in the centre. From skylight to floor was an immense column of swirling gas exactly the width of the oculus. It seemed to project the daylight straight down like a giant beam, a glowing pillar of pale light.
After gazing in awe for a moment they realized it was rocketing upwards at immense speed, giving the illusion that they themselves were hurtling inexorably downward into the fiery depths of the volcano. All their instincts told them there should be a deafening roar yet the chamber was eerily quiet.
“It’s water vapour,” Costas finally exclaimed. “So this is what happens to the rainwater that isn’t channelled out. It must be like a blast furnace down there.”
The increasing heat they had felt during the ascent was emanating from the chimney in front of them.
They were standing on the outer edge of a wide platform that ran round the rotunda several metres above the central floor. Evenly spaced doorways, identical to the one they had just emerged from, had been cut into the rock all the way round the perimeter. Each one was topped with the now familiar symbols. Beyond the inside edge of the platform they could just make out the central dais of the chamber. Backing onto the vapour column were four stone seats, each in the shape of bull’s horns and arranged at cardinal points of the compass. The one facing them was obscured by the platform but was clearly larger than the others, the tips of the horns reaching up towards the oculus.
“It must be some sort of throne room,” Costas said, awestruck. “An audience chamber for the high priests.”
“The hall of the ancestors. The funerary chamber. And now the audience chamber,” Katya murmured. “This must be our last staging post to the holy of holies.”
They had been in a state of constant high excitement, exhilarated by the thrill of discovery since leaving the submarine. Now as they confronted the very core of the volcano their exuberance was tempered with unease, as if they knew the ultimate revelation would not be yielded without a price. Even Costas faltered, reluctant to abandon the security of the tunnel and pitch himself forward into the unknown.