Show 0 7 0 VOWS J MYSTERIES M OP OF NATURE by george frederick rederick r wright A rl LL D i L I 1 continent cont iner tilted up and down i 5 1 the level of the ocean cean n la ls more con a betant a n t t than b an that hat t of the land the expanse artt n s e 0 of t th the e ocean la Is three timos aa As great ae that of the lani ian and its dolth more than ten ton times as great it all the land should be bunk in the ocean it would raise the general wa ter level only about 30 feet in generalee general genera lwe we may aay say with perfect confidence that the ocean bed beds represent portion portions of the earths crust vim h have hav e been sinking from the earliest geol ideological times whilo while the continents represent those portions which with many oscillations have on the whole been rising it probably la Is cot not true aa as ta Is often stated that the areas ut of land and water have shifted places in ta past time so that continents continent were found where the main ocean beds now lie and oceans swept without interruption ter over the continental areas still there Is the best beet of at evidence that large portions ot at the existing continents were at various times bolow below the level of at the sea but while this Is true it seems equally certain that during the abst dence of these area areas below the aea sea level they existed either aa as shallow love 1 water borders of at the main continental areas arbas or as internal seas for example the great depth of sedimentary rocks which cover the mississippi basin extending from the allegheny mountains to tho the rocky mountains are shallow water deposit deposits so go shallow indeed was the water during long periods that it was little more than a swamp in which the vegetation that formed the numerous seams of coal could grow and flourish hut but the level was not constant after attar a jarge large accumulation of vegetable matter that could be turned into coal had taken place there was a slight and very gentle sinking of the whole area so that mud and sand were brought in from the neighboring higher lends to arm farm a complete covering for the coal oo 00 that when it was turned into rock I 1 Is was able to protect it and preserve it for future ages this process of at sacr slow but irregular sinking of the mis basin continued until thousands of feet of sedimentary material had been washed into it aa as the mia rt Is carrying sediment into the gulf omit pt mexico at the present time successive strata like the leaves reaves of at a book record the various downward movements of the long col coul coli I perica in other countries especially in england and china there la in the same earns record of long continued down ward movements of continental areas during the coal period it if this downward movement had bad continued always the coal would have been inaccessible beneath the depths of the sea where indeed much of it doea does still remain in nova scotia the beet beat seams of coal are mined many miles and at a depth of many marly hundred feet below the bottom of the sea in england also some of the best beat seams of at coal are followed out underneath the sea ties and it Is supposed that coat coal velas are continuous from southern england to the continent far beneath the bottom of dover trait dut but fortunately tho the downward motion of the coal area was in due time arrested and had the contrary movement begun which has brought this priceless material within easy reach of men in the mountains of at pennsylvania and china in the hills of england and in the plateaux of the central and western states 0 america other illustrations of great in levels are too i nume numerous roaz a be ment ionel in detail 1 in colorado there was a g abdual aub sub of land below sea level during the carboniferous and eraa eras until from to 16 feet of sediment bad had accumulated over the sinking area but at the end of liat aliat 0 period the area began to rise and this rise baa has continued until the present time when it stands many thousand feet above the level of the sea similar witness to such changes of level la Is borne by extensive sedimentary rocks containing abundant beb shells of late geological ago age which are found at a height of feet above the sea on the pyrenees Pyre nees ea the alps aps and the caucasus mountains and at a height of feet upon the mountains of central asia A map of tho eastern continent during the early part of the tertiary period shows a irrean mediterranean sea covering all central europe and ancl extending into asia submerging the highlands of and most of the mountains of Turk turkestan estan but that this was not net a 8 general subsidence of tho the continents is evident from the simple fact th that sediment meat these areas are covered with wilb sedi n tary strata if it mud and sand and all d gravel are deposited in water t there here must powe area not far away from h they could be derived while these general facts concerning change changes in land lerel level in ancient geological time times beyond all question are very less attention loa than they ther merit alx been given to the facts showing that corresponding change chances are are cull going on and haye bays produced striking results within re cent times and arid point to interesting lne conclusions with reference to the fu tu ur ure I 1 with the glacial i period which Is the most recent of all the geological epochs these change of 0 level terel are very evident and connect themselves thenia elvea with the early history ot at mankind at the close of the tertiary period which culminated in the glacial era the central and northern part of north america stood at a level of 0 2000 or feet above that t st 1 present occur occupies iu this ie Is proved by the existence of at innumerable channel channels now deeply burled buried by glacial debris dobris or extending out into the ocean across a the shallow submerged shelf 1 of the continent both upon the atlantic ard pacific coasts in illinois in ohio and in central new york thole burled buried channels are found down below sea level showing that the land must have been very much elevated to allow the streams which crossed these theme rocky gorges to make their way to the aea sea from these distant inland points the cities of cleveland 0 and syracuse N Y are built over euch such burled gorges the delaware the hudson and add the st lawrence rivers rive then emptied into the sea sta run ning through deep gorges or canyons which crossed A level coastal plain the fiorda of greenland and of at norway and of the pacific coast of north america bear similar testimony monr since they probably inmost cases mark the lines of ancient rivers which coursed through them to the aea sea when tha the land via nao so kuch much elevated that what are now tle bottoms of abeso channels cb annela were occupied by rushing mountain torrente torrents in short these theme fiords are drowned river valley valleys but at the close of the glacial period the land levels in all thie this northern region were much lower than thitu at the present time on the southern coast of new england sea beaches were thrown up about fifty feet beet higher than those which are formed now along the southern shore of maine the land bad had sunk so much that sea shells are found in clay deposits feet above the present sea level the champlain and st lawrence valley was so much depressed that whales sported in water over the site of middlebury col cot lege vermont vemont and seals ventured into an arm of at the sea extending far ul up into the ottawa river while at moo mou treat modern modem sea shells are found feet above present tide water upon the top of the mountain which give gives the city its name going farther north the indications are that upon the shores abores of the arctic sea post florial subsidence amounted to 1000 fiet everywhere across the continent there ie in cumulative evidence that thie thin subsidence was aa an exten live dathe da as the glaciated region and that it t increased in amount from south to north this Is a very important consideration Ide ration to be kept in mind in working out glacial and problems this differential northerly depression press fort at the close of the glacial period caused the great lakes to flow at first into the ottawa across lake over the site alt of north bay into the mattaway river and 60 into the along the line through which tho the canadian govern ment is talking of building a hip ship canal and which ie Is already utilized by the canadian pacific railroad this pass 1 in now lesa less than feet above the level of at the lakes i copyright toy by joeeph 13 bowl dowles |