relation to catastrophes like the eruption of Thera.”
They were finning towards the pedestal in the centre of the chamber, their beams converging on the edge of the sacrificial platform. As the top came into view they were confronted by an image almost too fantastic to comprehend, a spectre that vanished like a genie as soon as they came close to it.
“Did you see what I saw?” Katya breathed.
“Extraordinary,” Costas murmured. “The bones must have disintegrated thousands of years ago, but in the stillness the calcium salts remained where they fell. The slightest disturbance and it disappeared like a puff of smoke.”
For a split second they had seen a recumbent bull, its giant shape reduced to an imprint of white streaks like a faded photographic negative. In the corners of the table they could make out holes where its limbs had been tied down before the sacrifice, the rope long since disappeared as the seawater rose and took the carcass in its icy embrace.
Jack picked up a dagger lying on one side of the table. The stone handle was incised with a fearsome beast, half bull, half eagle.
“There’s your answer,” he said softly. “The courtyard with the colossal statue by the shoreline was the world’s first bullfighting arena. The doomed animals were led up the processional way between the pyramids and then driven up the stairs to this slab. It would have been a spectacular site, overlooking the entire city on the plain below, the sacrifice perhaps timed to coincide with the first flash of sunlight overhead through the twin peaks of the volcano to the horns of the bull-sphinx in the courtyard far below. The whole city must have come to a standstill.”
He paused and looked at the other two solemnly through his visor. “We’ve just borne witness to the final sacrifice, the last desperate attempt by the priests to repel the rising seas before the doors to this chamber were locked shut for all time.”
They finned over the altar and headed towards a yawning black hole in the rear of the chamber. The shimmer grew more intense as they swam forward, the light from their headlamps sparkling off the walls as if they were billowing curtains of crystal and gold.
“
Just before they reached the portal, Costas veered off to the right, his beam reduced to a narrow orb as he closed in on the wall.
“It’s iron pyrites, fool’s gold.” His voice was hushed in awe. “The crystals are so large and close-set they look like gold plate until you get close up.”
“But the island’s volcanic, made of igneous rock,” Katya said.
“Mainly basalt,” Costas agreed. “Molten magma that cooled too quickly for mineral crystals to form. The basalt between the cliff and the ancient shoreline was low in silica so cooled slowly as it flowed out over the limestone substrate. Further up it formed from acidic lava rich in silica that solidified as soon as it hit the surface. In the Aquapods we saw fissures of obsidian, the black volcanic glass that forms when rhyolitic lava is quickly chilled.”
“Obsidian blades were the sharpest known until the development of high-carbon steel in the Middle Ages,” Jack said. “That dagger was obsidian.”
Costas came towards them along the back wall. “Incredible,” he mused. “Obsidian for tools, tufa for masonry, volcanic dust for mortar, salt for food preservation. Not to mention the richest farmland anywhere and a sea teeming with fish. These people had it all.”
“What about the granite in the doors?” Katya persisted.
“Also igneous,” Costas replied. “But it’s not the result of volcanic eruption. It’s an intrusive rock that forms deep in the earth’s crust as the magma slowly cools, producing crystalline structures dominated by feldspar and quartz. It’s called plutonic after the Greek god of the underworld. It was thrust upwards by plate tectonics.”
“That explains another resource,” Jack interjected. “The pressure also metamorphosed seabed limestone into marble, providing fine-grained stone for those sculptures outside. There must be outcrops lower down these slopes and on that ridge to the west.”
“We’re inside a composite volcano,” Costas continued. “A combination cinder cone and shield volcano, the lava interlayered with pyroclastic ash and rock. Think Mount Saint Helens, Vesuvius, Thera. Instead of building up behind a plug and erupting explosively the magma wells up through a folded outcrop of plutonic rock and solidifies as a basaltic shield, an event repeated every time the pressure builds up. My guess is that the deeper reaches of this rock are a seething cauldron of gas and lava that force their way through fissures to leave a honeycomb of passageways and caverns. Deep down this volcano is literally riddled with rivers of fire.”
“And the fool’s gold?” Katya asked.
“An unusually dense node of iron forced up with the granite. Slow cooling deep in the earth’s crust formed huge crystals. They’re fabulous, a unique discovery.”
They turned back for one last look at the world they were leaving. In their headlamps the water was suffused with colour, the light sparkling off the rock in a shimmer of gold.
“This chamber is a geologist’s dream,” Costas murmured reverentially. “Polish it up and you’ve got a spectacle that would dazzle any onlooker. To the priests it must have seemed a godsend. An awesome complement to the pyrotechnics of the volcano itself.”
Beyond the silhouette of the altar they could just make out the casing of the submarine at the end of the tunnel. It was a reminder of the sinister enemy that barred their way back to the world above, that their only hope of rescue for Ben and Andy lay in the pitch-blackness ahead.
Before confronting the forbidding darkness of the portal, Costas finned back to the centre of the chamber. He extracted an item from his tool belt and swam round the altar before returning, an orange tape reeling out of a spool on his backpack.
“It’s something I thought of when you were telling us of legends that hark back to conflict between the Mycenaeans and Minoans in the Bronze Age,” he explained. “When Theseus arrived at Knossos to kill the Minotaur he was given a ball of thread by Ariadne to guide him through the labyrinth. Under this rock we have no access to GPS and can only navigate by dead-reckoning with compass and depth gauge. Ariadne’s thread may be the only safety line we’ve got.”
Jack led the way out of the sacrificial chamber and through the portal, his headlamp trained on the tunnel ahead. After about ten metres the passageway narrowed and curved off to the right. He paused to let the other two draw up on either side of him, the space just wide enough to accommodate them line abreast.
They were alone in the deathly stillness of a place no human had entered since the dawn of civilization. Jack experienced a familiar surge of excitement, the burst of adrenaline briefly alleviating the debilitating effects of his wound and urging him on into the unknown.
The passageway began to snake along in alternating curves, each bend seeming to exaggerate the distance from the entrance. The experience was strangely disorientating, as if the ancient architects of this world had known the unsettling effect the absence of straight lines had on the human sense of direction.
They paused while Costas paid out the final length of tape and attached a fresh spool to his back. In the narrow confines, their lamps cast a brilliant light on the walls around them, the surface lustrous as if it had been kept polished over the millennia.
Jack finned a few metres ahead and noticed an aberration in the wall.
“I’ve got markings.”
The other two quickly swam up to join him.
“Man-made,” Costas asserted. “Chiselled into the rock. They’re just like the cartouches around those precursor hieroglyphics Hiebermeyer found on that ancient stone in the temple where Solon visited the high priest.”
Hundreds of nearly identical markings were aligned in twenty horizontal registers that extended beyond the next curve in the passageway. Each marking comprised a symbol surrounded by an oval border, the cartouche Costas had referred to. The symbols within the cartouches were rectilinear, each with a vertical stem and containing varying numbers and arrangements of horizontal bars branching off to either side.
“They look like runes,” Costas said.
“Impossible,” Katya retorted. “Runes derive from the Etruscan and Latin alphabets, from contact with the Mediterranean during the classical period. Six thousand years too late for us.”
