
IN THE EARLY YEARS OF THE twentieth century, an enormous bowl-shaped hole in the high plains of northern Arizona was investigated by a mining engineer and his associates. The hole was almost three quarters of a mile wide-a little over one kilometer9-and it penetrated thick layers...

IN THE EARLY YEARS OF THE twentieth century, an enormous bowl-shaped hole in the high plains of northern Arizona was investigated by a mining engineer and his associates. The hole was almost three quarters of a mile wide-a little over one kilometer -and it penetrated thick layers...