“It came in vertically, punching a whole ten kilometres wide through the atmosphere, generating temperatures so high that the air itself started to burn. When it hit the ground, rock turned to liquid and spread outwards in mountainous waves, not freezing until it had formed a crater two hundred kilometres across.
That was only the beginning of disaster; now the real tragedy began.
Nitric oxides rained from the air, turning the sea to acid. Clouds of soot from incinerated forests darkened the sky, hiding the sun for months. Worldwide, the temperature dropped precipitously, killing off most of the plants and animals that had survived the initial cataclysm. Though some species would linger on for millenia, the reign of the great reptiles was finally over.
The clock of evolution had been reset; the countdown to man had begun.”
—Arthur C. Clarke in ‘The Hammer of God’