coal

59:5.1The ap­pear­ance of fish dur­ing the pre­ced­ing pe­riod marks the apex of ma­rine-life evo­lu­tion. From this point on­ward the evo­lu­tion of land life be­comes in­creas­ingly im­por­tant. And this pe­riod opens with the stage al­most ide­ally set for the ap­pear­ance of the first land an­i­mals.

59:5.2220,000,000 years ago many of the con­ti­nen­tal land ar­eas, in­clud­ing most of North Amer­ica, were above wa­ter. The land was over­run by lux­u­ri­ous veg­e­ta­tion; this was in­deed the age of ferns. Car­bon diox­ide was still pres­ent in the at­mo­sphere but in less­en­ing de­gree.

59:5.3Shortly there­after the cen­tral por­tion of North Amer­ica was in­un­dated, cre­at­ing two great in­land seas. Both the At­lantic and Pa­cific coastal high­lands were sit­u­ated just be­yond the pres­ent shore lines. These two seas pres­ently united, com­min­gling their dif­fer­ent forms of life, and the union of these ma­rine fauna marked the be­gin­ning of the rapid and world-wide de­cline in ma­rine life and the open­ing of the sub­se­quent land-life pe­riod.

59:5.4210,000,000 years ago the warm-wa­ter arc­tic seas cov­ered most of North Amer­ica and Eu­rope. The south po­lar wa­ters in­un­dated South Amer­ica and Aus­tralia, while both Africa and Asia were highly el­e­vated.

59:5.5When the seas were at their height, a new evo­lu­tion­ary de­vel­op­ment sud­denly oc­curred. Abruptly, the first of the land an­i­mals ap­peared. There were nu­mer­ous species of these an­i­mals that were able to live on land or in wa­ter. These air-breath­ing am­phib­ians de­vel­oped from the arthro­pods, whose swim blad­ders had evolved into lungs.

59:5.6From the briny wa­ters of the seas there crawled out upon the land snails, scor­pi­ons, and frogs. To­day frogs still lay their eggs in wa­ter, and their young first ex­ist as lit­tle fishes, tad­poles. This pe­riod could well be known as the age of frogs.

59:5.7Very soon there­after the in­sects first ap­peared and, to­gether with spi­ders, scor­pi­ons, cock­roaches, crick­ets, and lo­custs, soon over­spread the con­ti­nents of the world. Dragon flies mea­sured thirty inches across. One thou­sand species of cock­roaches de­vel­oped, and some grew to be four inches long.

59:5.8Two groups of echin­o­derms be­came es­pe­cially well de­vel­oped, and they are in re­al­ity the guide fos­sils of this epoch. The large shell-feed­ing sharks were also highly evolved, and for more than five mil­lion years they dom­i­nated the oceans. The cli­mate was still mild and equable; the ma­rine life was lit­tle changed. Fresh-wa­ter fish were de­vel­op­ing and the trilo­bites were near­ing ex­tinc­tion. Corals were scarce, and much of the lime­stone was be­ing made by the crinoids. The finer build­ing lime­stones were laid down dur­ing this epoch.

59:5.9The wa­ters of many of the in­land seas were so heav­ily charged with lime and other min­er­als as greatly to in­ter­fere with the prog­ress and de­vel­op­ment of many ma­rine species. Even­tu­ally the seas cleared up as the re­sult of an ex­ten­sive stone de­posit, in some places con­tain­ing zinc and lead.

59:5.10The de­posits of this early Car­bonif­er­ous age are from 500 to 2,000 feet thick, con­sist­ing of sand­stone, shale, and lime­stone. The old­est strata yield the fos­sils of both land and ma­rine an­i­mals and plants, along with much gravel and basin sed­i­ments. Lit­tle work­able coal is found in these older strata. These de­po­si­tions through­out Eu­rope are very sim­i­lar to those laid down over North Amer­ica.

59:5.11To­ward the close of this epoch the land of North Amer­ica be­gan to rise. There was a short in­ter­rup­tion, and the sea re­turned to cover about half of its pre­vi­ous beds. This was a short in­un­da­tion, and most of the land was soon well above wa­ter. South Amer­ica was still con­nected with Eu­rope by way of Africa.

59:5.12This epoch wit­nessed the be­gin­ning of the Vos­ges, Black For­est, and Ural moun­tains. Stumps of other and older moun­tains are to be found all over Great Britain and Eu­rope.

59:5.13200,000,000 years ago the re­ally ac­tive stages of the Car­bonif­er­ous pe­riod be­gan. For twenty mil­lion years prior to this time the ear­lier coal de­posits were be­ing laid down, but now the more ex­ten­sive coal-for­ma­tion ac­tiv­i­ties were in pro­cess. The length of the ac­tual coal-de­po­si­tion epoch was a lit­tle over twenty-five mil­lion years.

59:5.14The land was pe­ri­od­i­cally go­ing up and down due to the shift­ing sea level oc­ca­sioned by ac­tiv­i­ties on the ocean bot­toms. This crustal un­easi­ness—the set­tling and ris­ing of the land—in con­nec­tion with the pro­lific veg­e­ta­tion of the coastal swamps, con­tributed to the pro­duc­tion of ex­ten­sive coal de­posits, which have caused this pe­riod to be known as the Car­bonif­er­ous. And the cli­mate was still mild the world over.

59:5.15The coal lay­ers al­ter­nate with shale, stone, and con­glom­er­ate. These coal beds over cen­tral and east­ern United States vary in thick­ness from forty to fifty feet. But many of these de­posits were washed away dur­ing sub­se­quent land el­e­va­tions. In some parts of North Amer­ica and Eu­rope the coal-bear­ing strata are 18,000 feet in thick­ness.

59:5.16The pres­ence of roots of trees as they grew in the clay un­der­ly­ing the pres­ent coal beds demon­strates that coal was formed ex­actly where it is now found. Coal is the wa­ter-pre­served and pres­sure-mod­i­fied re­mains of the rank veg­e­ta­tion grow­ing in the bogs and on the swamp shores of this far­away age. Coal lay­ers of­ten hold both gas and oil. Peat beds, the re­mains of past veg­etable growth, would be con­verted into a type of coal if sub­jected to proper pres­sure and heat. An­thracite has been sub­jected to more pres­sure and heat than other coal.

59:5.17In North Amer­ica the lay­ers of coal in the var­i­ous beds, which in­di­cate the num­ber of times the land fell and rose, vary from ten in Illi­nois, twenty in Penn­syl­va­nia, thirty-five in Al­abama, to sev­enty-five in Canada. Both fresh- and salt-wa­ter fos­sils are found in the coal beds.

59:5.18Through­out this epoch the moun­tains of North and South Amer­ica were ac­tive, both the An­des and the south­ern an­ces­tral Rocky Moun­tains ris­ing. The great At­lantic and Pa­cific high coastal re­gions be­gan to sink, even­tu­ally be­com­ing so eroded and sub­merged that the coast lines of both oceans with­drew to ap­prox­i­mately their pres­ent po­si­tions. The de­posits of this in­un­da­tion av­er­age about one thou­sand feet in thick­ness.

59:5.19190,000,000 years ago wit­nessed a west­ward ex­ten­sion of the North Amer­i­can Car­bonif­er­ous sea over the pres­ent Rocky Moun­tain re­gion, with an out­let to the Pa­cific Ocean through north­ern Cal­i­for­nia. Coal con­tin­ued to be laid down through­out the Amer­i­cas and Eu­rope, layer upon layer, as the coast­lands rose and fell dur­ing these ages of seashore os­cil­la­tions.

59:5.20180,000,000 years ago brought the close of the Car­bonif­er­ous pe­riod, dur­ing which coal had been formed all over the world—in Eu­rope, In­dia, China, North Africa, and the Amer­i­cas. At the close of the coal-for­ma­tion pe­riod North Amer­ica east of the Mis­sis­sippi val­ley rose, and most of this sec­tion has ever since re­mained above the sea. This land-el­e­va­tion pe­riod marks the be­gin­ning of the mod­ern moun­tains of North Amer­ica, both in the Ap­palachian re­gions and in the west. Vol­ca­noes were ac­tive in Alaska and Cal­i­for­nia and in the moun­tain-form­ing re­gions of Eu­rope and Asia. East­ern Amer­ica and west­ern Eu­rope were con­nected by the con­ti­nent of Green­land.

59:5.21Land el­e­va­tion be­gan to mod­ify the ma­rine cli­mate of the pre­ced­ing ages and to sub­sti­tute there­for the be­gin­nings of the less mild and more vari­able con­ti­nen­tal cli­mate.

59:5.22The plants of these times were spore bear­ing, and the wind was able to spread them far and wide. The trunks of the Car­bonif­er­ous trees were com­monly seven feet in di­am­e­ter and of­ten one hun­dred and twenty-five feet high. The mod­ern ferns are truly relics of these by­gone ages.

59:5.23In gen­eral, these were the epochs of de­vel­op­ment for fresh-wa­ter or­gan­isms; lit­tle change oc­curred in the pre­vi­ous ma­rine life. But the im­por­tant char­ac­ter­is­tic of this pe­riod was the sud­den ap­pear­ance of the frogs and their many cousins. The life fea­tures of the coal age were ferns and frogs.

• between glacial layers

59:6.6Grad­u­ally the in­land lakes and seas were dry­ing up all over the world. Iso­lated moun­tain and re­gional glaciers be­gan to ap­pear, es­pe­cially over the South­ern Hemi­sphere, and in many re­gions the glacial de­posit of these lo­cal ice for­ma­tions may be found even among some of the up­per and later coal de­posits. Two new cli­matic fac­tors ap­peared—glacia­tion and arid­ity. Many of the earth’s higher re­gions had be­come arid and bar­ren.

60:2.7The flora of this age was much like that of the pre­ced­ing. Ferns per­sisted, while conifers and pines be­came more and more like the pres­ent-day va­ri­eties. Some coal was still be­ing formed along the north­ern Med­i­ter­ra­nean shores.

60:3.9The de­posits of chalk and green­sand marl give name to this pe­riod. The sed­i­men­ta­tions of these times are var­ie­gated, con­sist­ing of chalk, shale, sand­stone, and small amounts of lime­stone, to­gether with in­fe­rior coal or lig­nite, and in many re­gions they con­tain oil. These lay­ers vary in thick­ness from 200 feet in some places to 10,000 feet in west­ern North Amer­ica and nu­mer­ous Eu­ro­pean lo­cal­i­ties. Along the east­ern bor­ders of the Rocky Moun­tains these de­posits may be ob­served in the up­tilted foothills.

61:2.335,000,000 years ago marks the be­gin­ning of the age of pla­cen­tal-mam­malian world dom­i­na­tion. The south­ern land bridge was ex­ten­sive, re­con­nect­ing the then enor­mous Antarc­tic con­ti­nent with South Amer­ica, South Africa, and Aus­tralia. In spite of the mass­ing of land in high lat­i­tudes, the world cli­mate re­mained rel­a­tively mild be­cause of the enor­mous in­crease in the size of the tropic seas, nor was the land el­e­vated suf­fi­ciently to pro­duce glaciers. Ex­ten­sive lava flows oc­curred in Green­land and Ice­land, some coal be­ing de­posited be­tween these lay­ers.