WHAT WILL REMAIN IN A MILLION YEARS?

By considering the longevity of human works in the future, and thereby placing our existence into the larger context of geologic time, the long-term impacts of humans can be realized. I pose this question, “If human alteration of the Earth were to immediately cease, what would remain in a million years?”

Assumptions of climate change, such as the return of glacial conditions, must be made. This will bring ice sheets, new tills, and freeze-thaw weathering conditions. Sea level lowering will establish new base levels and produce worldwide fluvial incision.

Most dams occupy active channels that will be subjected to incision and higher stream flows. Reservoir overtopping will cause frequent dam failures. High stream discharge will remove most embankments, but remnants of massive concrete dams (Boulder) or masonry dams (Roosevelt), could survive. The second major reservoir failure mechanism will be deterioration and failure of the metal or concrete outlet works.

Weathering of building materials will drastically alter man-made structures. Concrete will crack and allow rebar to oxidize, destroying most concrete. Oxidation will destroy steel structures. No concrete or steel bridges will survive. Older structures like the Roman Aqueducts, which have survived for 2,000 years, will experience stone deterioration or seismic damage. Concrete and asphalt pavements will either crumble or be overgrown.

The Pacific Plate, with a slip rate of 25mm/year along the San Andreas fault, will move north 15½ miles relative to the American Plate. Palm Springs will be where San Bernardino used to be. Over 100,000 magnitude 6.0 earthquakes will occur. There will be hundreds of larger earthquakes. Few structures will be standing in Southern California. Mammoth Mountain will erupt and deposit tuff over western Nevada, central and southern California.

So what will survive? Large open pit mines in places such as Arizona will be lakes. The Egyptian pyramids, if not buried, will be minor topographic features. Aluminum soft drink cans and pieces of glass will remain. Many of these will be preserved in sanitary landfills. The future perception of the Earth’s surface will be radically different than our view today.