the grand canyon of arizona-第23章

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ey。　It　may　therefore　be　accepted　as　a　fairly　accurate　and　authoritative　presentation　of　the　geological　conditions　existent　at　the　Canyon；　with　their　explanations；　as　accepted　by　the　leading　scientists　of　to…day。


The　beginning　of　land。　In　the　long　ago　centuries；　when　the　world　was　〃without　form　and　void；〃　waters　covered　the　face　of　the　earth；　and　darkness　brooded　over　the　waters。　As　the　earth's　crust　began　to　shrink　under　the　water；　in　the　process　of　cooling；　the　first　masses　to　crumple　up；　to　wrinkle；　were　the　first　to　arise　above　the　surface　of　the　vast；　primeval；　shoreless　ocean。　They　appeared　as　tiny　islands；　pinnacles；　or　ridges　thrust　up；　exactly　as　we　see　them　sometimes　on　the　coast；hidden　at　high　tide；　appearing　again　at　low　tide。

The　Laurentian　Hills。　Nature　had　plenty　of　time　before　her；　so　she　did　not　hurry　her　work；　and　it　took　long　centuries　before　there　was　any　large　amount　of　land　thrust　up　out　of　the　bosom　of　the　sea。　The　scientists　are　able　to　tell　us；　with　some　definiteness；　which　came　forth　first。　They　say　that　on　the　continent　of　America　the　earliest　born　land　was　a　mass　of　granitic　rock　in　Canada；the　Laurentian　Hills。　The　next　to　peer　above　the　surface　and　feel　the　warmth　of　the　sun　were　peaks　and　ridges　that　made　islands　of　themselves；　in　what　are　now　known　as　the　Rocky　Mountains　and　the　Appalachians。　Now；　at　last；　the　great　waves　of　the　sea　and　the　resistless　storms　had　something　to　play　with；　and　they　pounced　down　upon　the　land　as　with　tooth　and　claw。　They　rubbed　and　pounded；　raged　and　smashed　for　a　thousand　years；　and　then　another　thousand；　and　still　another；　while　Mother　Earth　uneasily　thrust　forth　her　rocky　children　out　of　the　ocean　into　the　light　of　day。　Surprised　at　such　treatment　by　the　storms　and　seas；　the　newly　born　earth　masses　began　to　crumble　and　〃weather。〃　The　detached　fragments　slipped　back；　or　were　washed　back；　into　the　deeper　or　shallower　parts　of　the　ocean；　and　were　there　tossed　back　and　forth；　pounded　and　ground　into　sand　and　silt；　into　pebbles　and　boulders；　while　more　land　was　slowly　being　thrust　out　for　the　angry　sea　to　work　upon。　Layer　by　layer；　the　ground…up　masses　were　deposited　in　the　inner　ocean　bed；　parts　of　which　were　now　practically　shut　off　from　the　vast　ocean　beyond。　How　many　centuries　of　centuries　this　process　continued　geologists　do　not　tell　us。　Time　is　so　vast；　so　long；　that　they　cannot　divide　those　early　days　into　weeks；　months　and　years；　as　we　now　do。

The　Continent　is　born。　After　many　millions　of　tons　had　been　thus　ground　up　and　tossed　about　and　mingled　with　the　waters　of　the　seas；　the　earth；　in　a　fit　of　fiery　anger；　turned　and　baked　them；　with　intense　heat；　out　of　all　semblance　to　their　former　appearance。　These　baked　masses；　in　the　course　of　time；　were　thrust　up　out　of　the　seas；　mashed　and　macerated　once　more；　again　deposited　as　sand；　silt；　pebbles　and　boulders；　and　again　burned。　These　processes　followed　each　other；　how　many　times　we　do　not　know；　the　earth　all　the　while　keeping　up　her　steady　uplift　of　the　children　of　her　bosom　out　of　the　great　sea。　Higher　and　higher　came　the　land。　Further　and　further　receded　the　sea；　until；　in　due　course；　the　sun　shone　upon　a　vast　area　of　land　that　was　the　rude　skeleton　of　what　is　now　the　continent　of　North　America。

It　would　have　taken　a　keen　eye；　however；　to　have　imagined　from　that　which　we　see　to…day　what　was　there。　The　Gulf　of　California　reached　far　up；　even　into　Nevada；　and　covered　what　are　now　the　Mohave　and　Colorado　Deserts；　there　was　no　California　Coast　Range；　the　Gulf　of　Mexico　was　vastly　larger　than　it　is　to…day；　covering　all　Florida；　and　reaching　up　the　Mississippi　Valley　half…way　to　the　Great　Lakes。

The　First　Strata。　It　was　just　preceding　the　last　uplift　of　this　epoch　that　the　era　of　deposition　of　rock　debris　was　so　prolonged　that　twelve　thousand　feet　of　strata　were　washed　into　the　bed　of　the　sea；　in　the　region　now　known　as　the　Grand　Canyon　Country。　It　was　at　the　time　when　life　was　beginning　to　dawn；　for　in　the　remnants　of　the　strata　are　found　fossils　of　the　earliest　known　life。　These　strata；　therefore；　are　of　immense　interest　to　the　geologist；　as　they　are　the　first　known　rocks　containing　life　to　emerge　from　the　primeval　sea。　Within　the　last　few　years；　they　have　been　called　the　Algonkian　Series；　and　later　I　shall　speak　of　them　more　freely。

Prior　to　the　deposition　of　these　Algonkian　strata；　the　Laurentian　rocks　（the　granite）　upon　which　they　rest　were　subject　to　a　long　period　of　〃planation；〃as　the　grinding　down　and　leveling　of　rock　surfaces　is　termed。　After　this　planation　was　complete；　a　subsidence　occurred；　the　whole　area　became　the　bed　of　an　inland　sea；　and　upon　the　planed…down　granite；　the　debris　that　formed　the　Algonkian　strata　was　washed。

While　they　were　being　deposited；　the　whole　region　was　the　scene　of　several　seismic　and　volcanic　disturbances；　for　great　dykes　and　〃chimneys〃　of　lava　are　found；　showing　clearly　that；　by　some　means　or　other；　the　strata　were　broken　and　shattered；　cracked　and　seamed；　and　that　through　these　cracks　the　molten　lava　oozedforced　up　from　the　interior　of　the　earth。　It　spread　out　over　the　Algonkian　rocks　in　small　sheets　or　blankets；　which　here　and　there　are　still　to　be　found　to…day。

Tilting　of　the　Algonkian　Strata。　Slowly　this　twelve　thousand　feet　of　strata　emerged　into　the　sunlight。　In　the　uplifting　processes；　the　surface　of　the　earth；　where　they　were；　became　tilted；　and　these　strata　therefore　〃dipped〃　or　〃tilted〃　away　from　the　perpendicular。　As　they　emerged；　weathering　and　erosion　began。　It　is　most　probable　that　this　process　of　degradation　began　and　continued　while　the　topmost　strata　were　at　or　near　sea　level；　so　that　it　was　a　simultaneous　process　with　the　uplift。

Erosion　of　the　Algonkian。　How　many　centuries　this　weathering　and　washing　away　process　consumed　no　one　knows。　At　the　close　of　this　epoch；　however；　the　Algonkian　strata　had　been　eroded　almost　away；　owing　to　its　tilted　condition；　so　that　in　some　places　even　the　surface　of　the　Archaean　was　exposed；　and　suffered　the　planing…down　process。　Figure　1　on　plate　facing　page　98　is　a　suggestion　as　to　the　possible　appearance　of　the　rocks　at　this　time。

Even　then；　in　those　far…away；　early　ages　of　history；　if　one　had　been　present　to　measure　these　strata；　he　would　have　discovered　the　astounding　fact　that；　although　he　had　measured　them　and　found　twelve　thousand　feet　before　they　began　to　emerge　from　the　ocean；　there　were　but　about　five　hundred　feet　of　them　left。　This　is　one　of　the　interesting　facts　in　geology；that　an　observant　reader　can　deduce　so　much　from　so　little。

The　twelve　thousand　feet　deposit。　〃But；〃　asks　the　layman；　〃I　cannot　possibly　see　how；　if　only　five　hundred　feet　of　strata　are　left；　any　one　could　ever　tell　that　there　were　once　twelve　thousand　feet。　If　eleven　thousand　five　hundred　feet　are　gone；　how　do　you　know　they　ever　existed？〃

A　very　reasonable　question　and　one　very　easily　answered。　Refer　to　the　sketch。　Let　the　bracket　on　the　right　show　the　present　width　of　the　remaining　strata；　viz：　five　hundred　feet。　Now　observe　the　tilted　condition　of　the　remnants。　To　get　the　original　height　of　the　depositions　begin　with　No。　1；　the　stratum　nearest　the　Archaean　and　measure　that。　Suppose　it　gives　us　five　hundred　feet。　No。　2　gives　two　hundred　feet；　No。　3；　five　hundred　feet；　No。　4；　one　hundred　and　seventy…five；　and　so　on　up　to　No。　14。　As　these　strata　were　deposited　horizontally；　all　we　have　to　do　is　to　mentally　replace　them　in　their　horizontal　position。　Throw　the　tilted　strata　back　again　into　their　original　condition；　and　by　this　method　of　measurement　it　is　seen　that　the　twelve　thousand　feet　can　be　made　up。　Figure　2；　facing　page　98。

Another　interesting　question　here　arises：　〃What　became　of　the　vast　quantity　of　sand　and　silt　and　pebbles　that　formed　and　were　carried　away　during　such　a　gigantic　process？　For；　think　of　it；　eleven　thousand　five　hundred　feet　of　strata；　or　rock；　two　miles　high；　almost　three　times　as　high　a　mass　as　the　present　distance　in　vertical　height　from　El　Tovar　to　the　river！　Where　has　it　all　gone？〃

Naturally　an　answer　to　these　questions　is　mere　conjecture；　as　only　from　a　study　of　the　facts　revealed　underneath　the　present　strata；　can　any　comparative　knowledge　be　gained　of　the　conditions　existent　at　that　prehis