| Show tChe he Depths of th the earth State of the Matter Forming the Earths Central Cubic Foot and What Would Happen Were Vere it Brought to the Surface Heat Far More Intense Than Any That Man Can Produce Copyright 1900 By N S Shaler Physical science has han undoubtedly at attained tamed tallied more than half its total devel development development development within the nineteenth century though it is true that the scientific I gains of the century do not include such splendid achievements as tat the Newton theory of gravitation the Co Ce account of the solar system or 01 the primary concepts of the atomic hypothesis The Thc rate of advance in scientific knowledge has been more uni uniform uniform uniform form also in the last Jast hundred years Ye rs then than in the earlier centuries The die dIs dIscoveries j in each field have served as asI I n ver t er before b tore to help belp on inquiries in ID ad adjacent adjacent adjacent jacent fields with the result that the explorers have hae moved forward in touch with one another Nearly every branch of ot science has thas helped and been helped by the others other To this interaction of learning a marked feature of our age we may amy in large measure attribute the surpassing advance it has won To it we clearly owe th singularly rapid gain which has bas been made mede in all that relates to the explanation of the earth Geological science is not a a distinct branch of learning as is chemistry or astronomy It is a body of varied knowledge drawn from the stores of or all aU aUthe the others othern and so 90 combined as to ren ten render render tender der an account ac of or what has gone ne on in inand inand inand and upon this sphere The conditions under which the group of sciences termed geology has hItS devel developed developed developed have set certain important limits limite to its successes A hundred years yeaM ago the pioneers had just fairly begun to interpret the tangle of rocks which make up the crust of the earth I and to speculate as aa to the meaning of off die f evidence concerning the condition of o its ita interior From the point of view of scientific inquiry these speculations had but little beyond the po position position position to which they the had bad been brought by electricity a century before The Thereal Thereal Thereal real advance In the science was attained in the main by close study of the structure structure structure ture and attitude of the rocks together with the organic remains which those laid down own in water so often contain In this way Va the division of the past history of the earth into ages epochs or periods a task begun in earlier E times has been carried so far that we wew jj w have a fairly clear Idea as to the thew waty vay w y in which the record is divided Into nto chapters chapter and sections and a gen general general general I eral though still very incomplete of or the order of events evento on I those parts of the crust which have lifted above the lure level of the sea This nis s ore of facts enables us its fairly to I t so O much of or the history of the earth arth as 36 Is written in stratified rocks have at no time in their history burled buried t to a greater depth then than twenty to tf thirty miles below the Deepest Depths Hard to Stady While the th fa f E fe revealed led in the newer newet n 1 rectos those Which commonly ie in a little changed form near the are easy to be interpreted I there are ale difficulties in this work which increase in rapid measure as they con oon concern concern cern beds that have hae been I deeply buried burled The reason for tor this t ls fc lb that in proper proportion tion as ae the strata are covered by oth others othera ers era subsequently laid down they are brought into a region where they are subjected to a number of ot physical and chemical actions concerning we can know nothing by direct observation tion we cannot submit this sphere to dissection The be deepest mining work penetrates only about one of the way wa to the center So far as we can ascertain the oldest and for a time deepest buried rocks have haveD not D t been more than one OD or two score miles below the epa cpa a level The first and audin in some ways the most important t point that our century has made as to the depths of this sphere consists IH Ja a determination of or the heat of ot its interior and th the origin thereof The Th evidence of a high temperature in inthe inthe Inthe the depths of the earth afforded by b I hot sprints sprIngs and volcanoes is so clear cle r that the Greeks Gresha appear to have noted its meaning and to have haye conjectured the existence of some kind of a cen central central central fire burning after the manner of oC ofa oCa ofa a furnace This view Indeed appears a p rs to have been commonly held heid by all the early geologic ge inquirers who consid considered ered sired the facts So too it has long loris been known that tha there was wac wa in some me mines a distinct increase in heat to be notes noted in any considerably con descent The I main maln gain in this inquiry has consisted I of a determination as to the rate of in increase increase crease crea and the source muree of this high tem tern temperature temperature which exists in the depths Many careful ca Ul observations distributed over all the continents show us that for all an the distance we have penetrated ed with shafts and borings the in increase Increase Increase crease is at an average rate of one degree Fahrenheit approximately for foretiCh each fifty feet of ot depth At this rate the temperature at the center would attain to about degrees Earth Not Fluid Inside But there are are Ipe various y reasons why this tills intense Intene heat neat cannot really exist How H thea then can caD we account for the er error error error It may be explained by what whet we e emay may o e or compute as taking place in any aD cooling body bod It is a perfectly warrantable supposition that the earth at a remote period was in a state of igneous fluidity that the mass was ong kept at about the same tempera temperature ture by a process of boiling When the sphere assumed its present state of ap approximate approximate approximate proximate solidity its Us further cooling would have led to the chilling of the outer port pert while the central portion I I remained at near its original heat A little will m show that under these conditions we should have a rapid increase of temperature for per pea perhaps perhaps haps hape a few score ecore miles downward while below a certain lavel level the in increase increase crease of heat would be at a steadily diminishing rate the greater part of or ort the t ei Inter being hei g at a rather r uniform hat beat When the understanding of the evi ml evidence dence d nce derived from volcanoes had ad f canoed beyond the primitive notion that th they y were vore due to soma seine kind of subterranean combustion such as takes place in IB burning coal coat beds ts adopted the view that they proved the interior to bo be in a fluid state stale tan like molten glass glau or iron IroD It did not seem possible otherwise to account for the outpouring of or lavas Javas in ha such uch quantities that they have covered to t great depths areas many thousand square re miles in extent Further proof to the same Mme me effect effectS seemed S emed to be 00 afforded by the fact tact that wherever we have access acce s to crystalline rocks such as granite which have been brought into contact with other de tie deposits posits they have haye entered enter d fissures uce in a K away Kway 4 i way that toot shows that they were origin originally originally originally ally fluid The hypothesis is of internal fluidity appeared rod at the beginning of ot this to be tolerably well ap 84 approved approved proved it was Indeed Ind ed assumed by moat most writers and was Wag made the basis of many learned treatise tr a sea Steadily how however however however ever within the last laut half y the contributions from rom other branches of science have served to bring this view into doubt First it was W noted note flOt i that any melted rock rook shrinks in general to the amount of about bout 15 IS per cent of its bulk in solidifying and aDd in consequence nce of or this tends to sink as it freezes This tendency tend y to settle down into an interior fluid would d make it for the crust of a generally fluid earth to at attain attain tain tam a greater thickness than about half halt a mile batore it would be dragged down by gravitation As we know that the earth la is solid MIld at least twenty mi mum lee downward and probably is in that I state for several times timea that depth the idea id 8 of a thin crust lying as a a layer laer on ona ona ona a liquid interior Int was shaken The next nett ne t attack on the notion of in internal internal internal fluidity came caine from the astronomers astronomers mers mets It had long ong been known knowS that the attraction of the moon on the equatorial bulging of the earth or rather the difference in this pull on the parts of or that mast mR near to and away awa r from our satellite caused caus the polar axis to be constantly changing its position The geological hearing bearin of the movement Is found in inthe the fact that if the earth were fluid except for its crust the position of the polar axis would uld not be altered by the attraction but the sphere would change ha e shape in inthe inthe inthe the manner of a tide as the waters do under a similar impulse While the problem is complicated d and Ute the results not accepted by all students it seems seem from this argument most likely that tile the earth is as rigid as the th most moat mo t solid of its rocks Geologists Views Reviewed In face of the evidence aa to the Ute dif tilt difficulties difficulties of o reconciling the great heat ht of the he interior and the ejections of 0 with the evidence ce that shows it cannot be fluid geologists of or this century have hae had b d to review many m which they from last with they have had haAl modify their conception of solids soll e fluids 90 so tar far taran ao to clear away misconceptions tWo dIJ to our ence with materials on the surface of or orthe the earth The TIle phrase phra e hard bard as a areck areek areek reek reck expresses a high order of rigid rigidity rigidity rigidity ity or resistance to strain when judged by ordinary conditions such as we are accustomed to yet et when en deeply buried burled and subjected to the vast vat straws which are due to the contraction of the mass from front the constant loss Jose of the internal heat rocks creep in the direr direction tion of ot least pressure like Uke wax They twist and an fold as do sheets sheet of wet paper they behave in a manner maimer that we are not accustomed to associate with solidity We may see how bOi inadequate are the common views as to the strength of materials s by b observing what taken place when an shot et strikes a thick plate of steel such sueh as asis asis asIs is used to protect the vital parts parti of a battleship The shield is made of the th most rigid substance that has been bemi contrived Its resistance is far I greater than that of or any rock Yet when struck by the projectile it yields and aDd andis aDdis andis is pushed aside as earth by the plow It may ma splash sp ash as mud when a pebble is thrown upon it The facts facto above aboe set forth as wall wait as atI other considerations which it to Is not necessary to t present have led those geologists of 01 oi our time who are con concerned concerned concerned with the difficult problems of the earths interior to look upon that realm vealin in a different way rom front their predecessors p of a hundred years ago It is now generally believed that the temperature in the depths though not DOt DOtas as gr groat grat at as a it would be if it the rate of at increase in heat which we observe ob erve in ini i mines continued downward to the con cen center conter ter is still hot in a measure not DOt ap approached approached preached in any furnace or even eVeD in inthe Inthe inthe the electric arc are That this heat does now not resolve the matter into vapor as it QuId like materials on the surface or 01 even bring it to the fluid state s e Is te ex cx explained by b the action of the pressure PIE un unto to which it is subjected Pressure that Would Woold Wo d Solidify Air We know kno that pressure tends to con ena consolidate all ail substances Even the rela reJa relatively rel trifling amount of it that we can am apply appl by our arts will air If It we could expose expo e this fluid air to the too weight of a hundred bundred miles of overlying rock we e may fairly presume that its particles would be so driven together that it would become in a manner manners s lid It is true that the bent of the depths depth would tend to keep it from at attaining attaining taming solidity but we may well be believe believe lieve liev that the load would be even more effective in bringing it into that state It seems likely in a word vOrd that the ef effect r feet of cf that internal pressure due to the weight of the overlying matter in Inducing what we term solidity is greater than the effect of the heat in bringing matter into the fluid condi condition condition tion We e may bring the points above noted note 1 into a clear view if we consider what we would find if we could critically ex examine examine examine amine the cubic foot of matter which lies Jle in the very center c of the earth It Itis ItIs ItIs is pretty certain that we should find it hotter than anything has been on the th surface for some hundred million years hotter than anything we see ex except except except it may be the surface of the sun and other fixed stars We would doubtless find that the atoms or molecules of ot the mass were driven nearer together than the like units of surface materials and that it was more rigid than glass yet under the strains such as have flexed and tangled the rocks in mountain folds this bit of the central earth would as all the deep parts evi evidently dently do under like strains If we could complete this imaginary observation by b bringing the central bit bitof bit bitof bitof of the planet to the surface keeping it during the miles of journey in unchanged conditions of heat and pres pros pressure pressure sure until it was in the th air cli ir and anti then suddenly release rel its bo bond 1 f it would ex cx explode explode after the he manner or ot d fired gun gunpowder gunpowder gunpowder powder There is the evident question as to the relation of or volcanoes to the heated interior of the earth This is still sill much Continued on pace pau 1 IL a at t o i r TH t Con ed l 1 rage page 17 I debated b s Inclining to the 1 conclusion that volcanoes are ar aJ really su superficial In Inori origin ln that they have their source in tHe tJ thi f outer ou te r hundred miles or so of the crus cru r tullE anU oo net hat as was believed at the beginning of the century In the lne the 1 central n The fact that they are a r J limited white while active to the floor of the thet oceans ans and seas and to the I lands within a few hundred miles of I Ithe the Indicates s that they th y are not of very origin The most remarkable explanation n is that tha t th they y are due to the effect arising from tram the t e lay laying laying I ing lag down of Urata lit iii water ater Such uch deposits depo ats act as as s a a blanket blank t serving I ing lag to hold bold in n the rocks the heat that is r continually seeking ae king 0 o escape into the cold outer iP space of the heavens leavens The result is that It If twenty miles mUes of beds are laid down on any auy part of the earth I and we know of ot like bar hav having ha haing barlag ing lag been formed tInt lowe layers ln e and I Ithe the crystalline cock rock on which they lie i imay may come to have tt temperature te of |
