Swenson stared impassively at his face. Then, after a moment, she said, “That’s my field of study too. Dr. White’s my thesis advisor. Maybe I can help you.”
Decker smiled. He reached into his jacket, pulled out a piece of paper, and handed it to her. “Do you know what this is?”
Swenson studied it for a moment. “This looks like mega-tsunami data, built from a computer model.”
Decker looked confused. “Go on,” he said.
“It’s designed to predict a mega-tsunami’s height at inundation. Where did you get this? From Dr. White?”
“I know what a tsunami is,” said Decker. “A kind of tidal wave, right? But what’s a mega-tsunami?”
Swenson raised an eyebrow. “Tides are moon-made, Agent Decker,” she replied. “Tsunamis are earth-generated. Mega-tsunamis are formed when an entire mountain — or mountain range — collapses into the sea, usually due to seismic activity. Unlike regular tsunamis, which may be ten to fifteen meters tall and a few dozen meters long, mega-tsunamis can be hundreds, up to five hundred meters tall — or more — and hundreds of kilometers in length.”
Decker did the calculation in his head. That was a wave taller than the Empire State Building. It was incredible. “I had no idea,” he said.
“Most people don’t,” said Swenson. “And why should they? Mega-tsunamis are rare, occurring naturally every few thousand years. Here, let me show you.” She motioned toward him and disappeared into another room at the far end of the living room. It appeared to be a library or study. A pair of large bay windows overlooked the open sea.
Swenson slipped behind an antique walnut desk in the far corner, and started to peck away at a PC. “This is a computer-generated simulation,” she continued, not even looking up. She moved the mouse. She clicked. “It’s based on a model Dr. White’s been working on, the same as the one on your paper. Take a look.” She swung the monitor around. Decker sat down by the desk.
The screen featured a top-down view of the Atlantic. The animated image gradually descended until it focused on a chain of islands off the coast of northwest Africa. Then, the perspective shifted. It fell to earth, swung low across the waves, like a sea bird, and approached a solitary island at a startling speed.
The island grew larger and larger until it took up the entire screen, and Decker could see volcanic peaks, smoking and spewing steam, when a rent materialized along the seaward side. The entire western flank of the island tore away. The mass of rock and stone and forest and meadow and town and road began to slither toward the sea. As the crustal layer ripped apart, the landmass picked up speed. The entire island seemed to split in half, with one side sliding with a mighty crash into the ocean.
The splash gathered momentum: a spike, then, rising higher, a bell-shaped dome, slate gray, blue, and finally frothy white. It rose and rose and rose, dwarfing the remaining peaks, still standing mist-enshrouded, still still, intact, and strangely static, perched on the footstool of the island.
The camera angle of the animation gradually ascended, drawing him higher and higher into the air, in tandem with the splash. The bell-shaped mass crowned like a flower, bloomed, then mushroomed skyward, only to turn at last, and fall back on itself. The water plunged. The dome collapsed, spreading out in all directions, rippling the surface of the ocean like the upturned edges of a giant saucer, growing ever larger by the second. The perspective kept ascending, until Decker was looking at the entire Atlantic once again, from Africa to the Americas. The wave was visible even from this vantage point above the planet’s atmosphere. The eastern edge slammed up against the coast of Africa. He watched the western flank arc out across the vast expanse, like the drawing of a great bow on the surface of the sea.
“This is obviously stop-action animation,” Swenson said. “A mega-tsunami of this magnitude would take between six and seven hours — at the speed of a jet plane — to sweep across the Atlantic.” As she spoke, Decker watched the wave overcome the Caribbean, then Maine and Massachusetts in the north, as far south as Sao Luis and Rio in Brazil.
“Even this far from the hypocenter,” Swenson continued, “the wave would be as much as twenty stories high, or higher. But it wouldn’t collapse at landfall. Unlike tsunamis, mega-tsunamis don’t shoal up when they encounter shallow waters. The wave would continue across the coastal plain, up river mouths, for twenty kilometers, or more.”
Decker watched the water wipe away the east coast of the USA.
“Everything within the flood zone would be utterly destroyed,” she added. “From Cape Breton to Key West, each town and every city. More than forty million people would perish, thirteen percent of the U.S. population. And hundreds of millions would be injured, one out of every three Americans. It would cause trillions of dollars in damage. The entire U.S. economy would be disrupted for years, if not permanently crippled.”
The animation concluded and the file closed automatically. Decker stared at the folder for a moment longer. He was having a hard time digesting the scope of such a cataclysm. The mind turns off after a few hundred deaths. Forty million is simply inconceivable, unprocessable. He turned and looked at Swenson. She was sitting calmly behind Dr. White’s desk.
“It’s incredible,” he said at last. “It’s… I don’t know the word. Apocalyptic. Biblical. But how likely is it that this will ever happen?”
Swenson shook her head. “I’m afraid you don’t understand, Agent Decker. It’s not about likelihood. It’s a certainty. The only variable is time.” She tapped the keyboard once again and a map of the world appeared on the screen. “A mega-tsunami occurred quite recently in Lituya Bay. It stripped timber and soil off to a height of five hundred and twenty meters above sea level. Here.” She pointed to a spot in south Alaska. “Mega-tsunamis can be formed by a number of natural forces, not just by the collapse of mountain ranges. Underwater landslides, for example. Or a giant meteor or comet entering through the atmosphere and smashing into the sea. Like the one that caused the extinction of the dinosaurs. While such celestial collisions are extremely rare, landslides caused by seismic activity occur quite frequently — relatively speaking — both on land and under water.
“The Lisbon earthquake of 1755, for example, is said to have triggered a fifteen-meter wave that caused widespread destruction in Morocco, southern Spain, and as far away as Bimini in the Bahamas. Volcanic island collapses happen far less often. The last one occurred about four thousand years ago, on the island of Réunion in the Indian Ocean. Here,” she added, pointing to the map. “Luckily for us there are no mountain ranges in danger of slipping into the ocean any time soon. Of course, you never know. Nature works on her own timetable. Then again, the way we’re messing with the planet. With global warming and—”
“But from where,” Decker insisted, “would it be likely to originate, if such an event were to occur?”
“According to Dr. White, the next mega-tsunami will originate from here.” She pointed to a dot off the northwest coast of Africa. “There are seven volcanoes on La Palma in the Canary Islands. One still quite active — the Cumbre Vieja,” she said.
Swenson explained the science to him, how water builds up in volcanoes within vertical sheets of permeable rubble over thousands of years, like gigantic reservoirs, held back by impermeable dykes of hardened lava. “One day, due to seismic activity,” she said, “the water inside Cumbre Vieja will begin to heat, the pressure build, and the walls will come tumbling down — like dozens of Hoover Dams colliding against each other, a line of giant dominos, five hundred billion tons collapsing into the sea. The water will move away so fast that it won’t be able to flow back behind the landslide, thereby creating a large air cavity displacing far more water than the volume of the landslide itself. It will release five thousand trillion joules of kinetic energy, and create a dome of water almost one thousand meters high, and thirty to forty kilometers wide. And what goes up, of course… ”