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Budleigh Salterton, on the south coast of Devon, sits above the most frightening cliffs on Earth. They are not particularly high. Though you don’t want to stand beneath them, they are not especially prone to collapse. The horror takes another form. It is contained in the story they tell. For they capture the moment at which life on Earth almost came to an end.
The sediments preserved in these cliffs were laid down in the early Triassic period, just after the greatest mass extinction in the history of multicellular life that brought the Permian period to an end 252m years ago. Around 90% of species died, and fish and four-footed animals were more or less exterminated between 30 degrees north of the equator and 40 degrees south.
Most remarkably, while biological abundance (if not diversity) tends to recover from mass extinctions within a few hundred thousand years, our planet remained in this near-lifeless state for the following 5m years. In studying these cliffs, you see the precipice on which we teeter.
The lowest stratum at the western end of the beach is a bed of rounded pebbles. These are the stones washed off Triassic mountains by flash floods and deposited in great dumps by temporary rivers. Because the forests and savannahs that might have covered the mountains had died, there was nothing to hold the soil and subsoil together, so erosion is likely to have accelerated greatly.
At the top of the pebble bed is a stony desert surface. The pebbles here have been sculpted by the wind into sharp angles and varnished with shiny oxides, suggesting the surface was unchanged for a long time. Above it are towering red Triassic sand dunes. Through a quirk of erosion, these soft deposits have been sculpted into hollows that look uncannily like fanged and screaming skulls.
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James' World 2 
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