The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . the at the top the covering consisted of from six to tenfeet of sandj^ till with occasional bowlders five feet in diameter;below this were eighteen inches of crushed anthracite entirelyfit for the market; then came three-fourths of an inch of rottencoal mixed with angular specs of slate; then one inch of sandyclay with rolled and angula
The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . the at the top the covering consisted of from six to tenfeet of sandj^ till with occasional bowlders five feet in diameter;below this were eighteen inches of crushed anthracite entirelyfit for the market; then came three-fourths of an inch of rottencoal mixed with angular specs of slate; then one inch of sandyclay with rolled and angular quartzite and slate pebbles;then one-half inch of fine bright crushed coal; and below thisthe glaciated surface, shown in the illustration, the upperthree-fourths of an inch of which was so soft and fully rottedthat it could be scratched with the finger nail. Below thiswas an indefinite extent of solid bright marketable coal. Therecency of the glaciation appears in the fact that south of theglacial border, only one mile away, the coal is so disintegratedas to be worthless for many feet below the outcrop. At thesame time the covering in the glaciated area is so sandy andporous as to be very little protection to the surface of o -a a 3 Z BOUNDARY OF THE GLACIATED AREA, 155 Another noticeable characteristic of deposits over thisattenuated border is that the prevaiHng, highly oxidized mate-rial is mingled with a considerable amount of fresh unoxidizedmaterial brought from farther north, showing that the oxidi-zation was mainly preglacial, and that the age of the depositmust be reckoned from the accession of the fresh the effort to determine the age of these deposits from theextent of the oxidization, it also should be ever kept in mindthat the ice moved first over an area v^ hose surface had beendeeply disintegrated and oxidized during the long ages oftertiary time. It was the product of this disintegration whichwas first incorporated into the mass which was
Size: 1023px × 2443px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthoruphamwarren18501934, bookcentury1900, bookdecade1910
