 The air quality in the vicinity of the field, as recorded in the town of Arvin to the west, is among the worst in the United States.The Edison field, like the other fields in the bottomlands of the San Joaquin Valley, consists of a series of oil pools embedded in various types of traps within a thick section of Cenozoic sediments lying on top of ancient metamorphic basement rocks of Jurassic age.These basement rocks, which in the vicinity of the Edison field are primarily green schist containing calcite seams, slope from northeast to southwest with a depth of in the northeast part of the field to in the southwest, a distance of about .