Evolution

And to the south, the lid of sky began to glow an eerie orange. A breeze wafted a sharp, distinctive smell to her nose. Ozone. The smell of the sea. She thought of lapping water, the glittering fish of the shallows. She must get to the sea. She had always made her living from the sea; there she would be safe. With a mournful lowing even she couldn’t hear, she began to blunder in the direction of the scent, ignoring the grisly detritus under her feet.

The sea turtle had been fortunate. When the comet hit, she was cruising the sea bottom far from the impact zone.

Her kind was among the most primitive of the great reptile dynasties. But, primitive or not, this turtle was an effective hunter. Her body was undemanding, requiring only a twentieth as much food as a dinosaur of the same weight. Heavily protected by her powerfully reinforced shell, cautious even as a hunter, the only risks she ran in her life were the annual assaults she had to make on the beaches to lay her eggs, before hurrying back to the safety of the water.

Her brain was small, her consciousness dim. She lived alone, in a world of colorless monotony. She had no bonds with her parents or siblings, no real understanding that the eggs she laid would produce a new generation. But she was ancient, wary, enduring.

Now, though, something disturbed her blue, lonely world. A monstrous current began to drag the sea toward the south.

Grimly the turtle paddled at the water, heading downward. Her instincts, honed by millions of years of tropical storms, primed her with a simple instruction: dive deep, get to the bottom, find shelter.

But this was like no current she had ever experienced. Through the increasingly muddy and turbulent water she glimpsed much larger creatures, even giant pliosaurs, being dragged backward by this mighty tide. And as she descended she was battered by debris, helpless ammonites, clams, squid, even rocks torn from the floor.

At last she found soft mud. All her four fins working, she began to work her way into the dirt, ignoring the hail of objects that clattered off her shell. Eventually she would have to surface, for air and warmth; but she could last for a long time, perhaps until this monstrous storm had passed away.

But now the sea’s glimmering meniscus descended toward her — and the sea drained away — and she found herself in sunlight, with moist mud hissing all around her. Something like shock lit up her small mind. The world had turned upside down; this made no sense.

And now the sea bottom mud, exposed, began to shake.

By the shifting, strange light, at last the suchomimus saw the sea. With a hoarse cry of relief, she hurried forward.

But the sea ran away from her, exposing glistening mud. And as fast as she pursued it, the sea ran faster.

A fish flopped at her feet. She stopped and plucked it out of the dirty mud and popped it into her mouth. In the fish’s tiny awareness was a kind of relief; this death was quick compared to the grisly suffocation it had endured on the new beach.

The sea bottom, uncovered for the first time in millions of years, was a glistening floor of life. It was littered with clams, crustaceans, squid, fish, ammonites of all sizes, all of them drowning in the air.

Further south there were giant shapes. The suchomimus saw a giant plesiosaur, stranded like the rest. Eight meters long, it lay gasping on the mud with its four huge flippers splayed and broken around it. It struggled, tons of marine carnivore flipping this way and that, huge fins waving, savage teeth snapping in rage at the fate that had stranded it.

On any other day it would have been a remarkable sight. The suchomimus turned away, bewildered.

When she looked north to the land, she could see creatures creeping out of the devastated forests, the wind-scoured marshland. Many of them were ankylosaurs and other armored creatures, protected thus far by the heavy armor that had evolved to fend off the teeth and claws of tyrannosaurs. They crawled toward the exposed seabed, seeking sanctuary, to drink, to feed.

But now the ankylosaurs opened their mouths and began to retreat once more. The suchomimus watched them, baffled. They were bellowing, but she couldn’t hear them.

She turned back to face the sea. And then she saw what had frightened them.

As air, so water.

From the impact site, powered by the immense pulse of heat, a circular shock wave now marched outward through the body of the ocean. Its destructive power was limited because the impact had not occurred in deep ocean water. Still, as it neared the coastline of North America, the wave was already some thirty meters high. And as it reached the shallower water of the Texas coast, the tsunami gathered itself, rearing ten to twenty times its initial height.