In the first few seconds thousands of billions of tons of solid, molten, and vaporized rock were hurled into the sky.

On the coastal plain of the North American inland sea, the duckbill herds gathered around the pools of standing water. They hooted mournfully as they clustered and nudged each other. Predators, from chicken-sized raptors upwards, watched stray duckbill young with cold calculation. In one place a crowd of ankylosaurs had gathered, their dusty armor glistening, like a Roman legion in formation.

An orange glow could be seen deep in the south, like a second dawn. Then a thin, brilliant bar of light arrowed into the sky, straight as a geometrical demonstration — straighter, in fact, than a laser beam, for the beam of incandescent rock suffered no refraction as it pushed out through the hole in the Earth’s superheated air. All of this unfolded in silence, unnoticed.

The crocodile-faced suchomimus stalked the edge of the ocean, her long claws extended. Just as she did every day, she was looking for fish. The death of her mate days before was a dull ache, slowly fading. But life went on; her diffuse grief gave her no respite from hunger.

Elsewhere a group of stegoceras was foraging, scattered. These pachycephalosaurs were about as tall as humans. The males had huge caps of bone on their skulls, there to protect their small brains during their earth-shuddering mating competitions, when they would crash their heads together like mountain sheep. Even now two great males were battling, ramming their reinforced heads together, the bony clatter of their collisions echoing across the plains. This species had sacrificed much evolutionary potential to these contests. The need to maintain such a vast protective cap of bone had limited the development of the pachycephalosaur brain for millions of years. Locked in biochemical logic, these males cared nothing for shifting lights in the sky, or the double shadows that slid across the ground.

On this beach it was just another day in the Cretaceous. Business as usual.

But something was coming from the south.

By now the crater was a glowing bowl of shining, boiling impact melt, wide enough to have engulfed the Los Angeles area from Santa Barbara to Long Beach. And its depth was four times the height of Everest, its lip farther above its floor than the tracks of supersonic planes above Earth’s surface. It was a crater ninety kilometers across and thirty deep formed in minutes. But this tremendous structure was transient. Already great arching faults had opened up, and immense landslides, tens of kilometers wide, began to collapse the steep walls.

And the seabed was flexing. The Earth’s deeper rocks had been pushed down into the mantle by the comet’s hammer blow. Now they rebounded, rising up through twenty kilometers, breaking through the melt pool to the surface. The basement rock itself, almost liquefied, quickly spread out into a vast circular structure, a mountain range forty kilometers across, erected in seconds. Meanwhile water strove to fill the pit that had been dug into the ocean floor. And already ejecta debris was falling back onto the crater’s shifting floor, a rain of burning rock. Temperatures reached thousands of degrees — enough to make the air itself burn, nitrogen combining with oxygen to form poisons that would linger for years to come. It was a chaotic battle of fire, steam, and falling rock.

From the impact site, superheated air fled at interplanetary speeds. A great circular wind gushed out from the Yucatan, down into South America, and across the Gulf of Mexico. The shock wave was still moving at supersonic speeds ten minutes later, when it reached the coast of Texas.

To the south of the beach, the thin pillar of light had fanned outward. It became more diffuse, and changed color, becoming a deeper orange white. Tiny flecks of orange could be seen flying up around its base. And now a band of darkness spread over the southern horizon. Still, all this unfolded in silence. What was coming was still moving much more rapidly than sound. The dinosaur herds were oblivious; still the young Pachycephalosaurs battled, locked into their Darwinian dance.

But the birds and the pterosaurs knew the sky. A group of pterosaurs had been working the ocean, skimming low over the surface seeking to scoop up fish in their hydrodynamically elegant beaks. Now they turned and headed inland, flapping to gain speed. A flock of small, gull-like birds followed, rising up on gray-white wings that seemed to pulse in the glowing rock light.

Of the thousands of dinosaurs, only the suchomimus reacted to the light show. She turned to the south, and her slit pupils narrowed at what she saw. Some instinct made her splash away from the water to run higher onto the shore. The warm sand was soft under her feet, slowing her down. But still the suchomimus ran.

Two young raptors, working playfully at the shell of a stranded sea turtle, lifted their heads with speculative interest as she passed. A corner of the suchomimus’s clever mind rippled with alarm signals. She was breaking many of her innate rules; she was making herself vulnerable. But a deeper instinct told her that the stain of darkness spreading over the horizon was more of a threat than any raptor.

She reached a bank of low dunes. A ball of fur squirmed indignantly out from beneath her feet and fled with blurring speed.

Over the coastal plain, the light began to fade.

At last the dinosaurs were disturbed. The great herbivore herds, the duckbills and ankylosaurs, lifted their heads from their browsing and turned to face the south.

The fan of ascending rock was invisible now, hidden by a wall of darkness that spanned the horizon. But it was a moving wall whose front bubbled and writhed. Lightning flickered over the moving surface, making it shine purple white.

Even now, in these last seconds, there was little sense of strangeness. It was like an eerie twilight. Some of the dinosaurs even felt drowsy, as their nervous systems reacted to the reduced level of light.

Then, from out of the south, the shock front exploded. From silence to bedlam in a heartbeat. The front smashed the animal herds. Duckbills were hurled into the air, huge adults writhing, their lowing lost in the sudden fury. The competition among the hard-skulled stegoceras was concluded without resolution, never to be resumed. Some of the great ankylosaurs stood their ground, turning into the wind, hunkering down like armored bunkers. But the very ground was torn up around them, the vegetation ripped out and scattered; even the lakes explosively emptied of their water. The shallow dune exploded over the suchomimus, instantly burying her in gritty darkness.

But as quickly as it had come, the shock wave passed.

When she felt the ground’s shuddering cease, the suchomimus began to scrabble at the earth. She sneezed the grit out of her nostrils, her great translucent eyelids working to clear her eyes, and clambered to her feet.

She stepped forward gingerly. The new ground was rubble strewn, uncertain, difficult to walk on.

The coastal plain was unrecognizable. The dune that had sheltered her was demolished, the wind’s patient, centuries-long work erased in seconds. The plain was littered with debris: bits of pulverized rock, seabottom mud, even a few strands of seaweed and smaller sea creatures. Above her, clouds boiled, streaming north.

Still the noise continued, great crackling shocks that rained out of the sky as sound waves folded over on themselves. But the suchomimus heard none of this. She had been deafened in the first instant of the shock’s passage, her delicate eardrums crushed.

Dinosaurs lay everywhere.

Even the largest duckbills had been smashed to the ground. They lay, broken and twisted, under scattered sand and mud. A group of raptors lay together, their lithe bodies tangled up. Everywhere the old lay with the young, parents alongside their children, predators with their prey, united in death. Most disasters, like floods and fires, selectively affected the weakest, the young and the old and the ill. Or else they targeted species — an epidemic, perhaps, carried by an unwitting host across a land bridge between the continents. But this time, none had been spared, none save the very fortunate, like the suchomimus.