Annie Dillard turns her unflinching eye on the dirt that slowly buries everything that has ever lived:
(from page 122 of For the Time Being)
"Sand
Earth sifts over things. If you stay still, earth buries you, ready or not. The debris on the tops of your feet or shoes thickens, windblown dirt piles around it, and pretty soon your feet are underground. Then the ground rises over your ankles and up your shins. If the segeant holds his platoon at attention long enough, he and his ranks will stand upright and buried like the Chinese emperor's army.
Micrometeorite dust can bury you, too, if you wait: A ton falls on earth every hour. Or you could pile up with locusts. At Mount Cook in Montana, at eleven thousand feet, you can see on the flank a dark layer of locusts. The locusts fell or wrecked in 1907, when a swarm flew off course and froze. People noticed the deposit only when a chunk separated from the mountain and fell into a creek, which bore it downstream.
New York City's street level rises every century. The rate at which dirt buries us varies. The Mexico City in which Cortés walked is now thirty feet underground. It would be farther underground except that Mexico City itself has started sinking. Digging a subway line, workers found a temple. Debris lifts land an average of 4.7 feet per century. King Herod the Great rebuilt the Second Temple in Jerusalem two thousand years ago; the famous Western Wall is a top layer of old retaining wall near the peak of Mount Moriah. From the present bottom of the Western Wall to bedrock is sixty feet.
Quick: why aren't you dusting? On every continent, we sweep floors and wipe tabletops not only to shine the place, but to forestall burial.
It is interesting, the debris in the air. A surprising portion of it is spider legs, and bits thereof. Spider legs are flimsy, Oxford writer David Bodanis says, beause they are hollow. They lack muscles; compressed air moves them. Consequently, they snap off easily and go blowing about. Another unexpected source of aerial detritus is tires. Eroding tires shed latex shreds at a brisk clip, say the folks who train their microscopes on air. Farm dust joins sulfuric acid droplets (from burned fossil fuels) and sand from the Sahara Desert to produce the summer haze that blurs and dims valleys and coasts.
We inhale "many hundreds of particles in each breath we take," says Bodanis. Air routinely carries intimate fragments of rug, dung, carcasses, leaves and leaf hairs, coral, coal, skin, sweat, soap, silt, pollen, algae, bacteria, spores, soot, ammonia, and spit, as well as "salt crystals from ocean white-caps, dust scraped off distant mountains, micro bits of cooled magma blown from volcanoes and charred microfragments from tropical forest fires." These sorts of things can add up.
At dusk the particles meet rising water vapor, stick together, and fall; that is when they will bury you. Soil bacteria eat what they can, and the rest of it stays put if there's no wind. After thirty years, there is a new inch of topsoil. (Many inches of new topsoil, however, have washed into the ocean.)
We live on dead people's heads. Scratching under a suburb of St. Louis, archaeologists recently found thirteen settlements, one of top of the other, some of which lasted longer than St. Louis has. Excavating the Combe Grenal cave in France, paleontologists found sixty different layers of human occupation.
The pleasantly lazy people of Bronze Age Troy cooperated with the burial process. Instead of sweeping garbage and litter from their floors, they brought in dirt to cover the mess and tramped it down. Soon they stooped in their rooms, so they heightened the doors and roofs for another round. Invaders, too, if they win, tend to build new floors on roofs they ruined. By the nineteenth century, archaeologists had to dig through twenty-four feet of earth to find the monuments of the Roman Forum."