Changes in Altitude and Climate, during the Quaternary Era. 



Mississippi Basin and 

 nobthwakd. 



Terracing of river valleys. 

 Northward rise of area of 

 Lake Agassiz nearly com- 

 plete before the ice was melt- 

 ed on the country crossed 

 by Nelson River ; but rise 

 about Hudson Bay is still 

 going on ; 7,000 to 8,000 years 

 since ice-melting uncovered 

 Niagara and falls of St. An- 

 thony. 



COEDILLERAN REGION, 



Abundant deposition of en- 

 glacial drift. Stone imple- 

 ments in river gravels of 

 Ohio, Ind., and Minn. Lau- 

 rentian lakes held at higher 

 levels, and Lake Agassiz 

 formed in Red River basin, by 

 barrier of retreating ice, with 

 outlets over lowest points of 

 their present southern water- 

 shed. Marine submergence 

 300 to 500 feet on southwest 

 sido of Hudson Bay. 



Including a stage of con- 

 siderable uplift, with return 

 of humid conditions, Alpine 

 glaciation (third Glacial 

 epoch), and the second great 

 rise of Lakes Bonneville' and 

 Lahontan. Very recent sub- 

 sidence and change to pres- 

 ent aridity. 



Europe and Asia. 



Erosion and terracing of 

 stratified drift in river valleys. 

 Land passage of European 

 flora to Greenland; succeed- 

 ed by subsidence there, ad- 

 mitting warm currents to 

 Arctic Sea. Minor climatic 

 changes, including a warmer 

 stage than now. Upper and 

 outer portions of Indo-Gan- 

 getic alluvial plain; extensive 

 deposits of Hwang Ho, and 

 destructive changes of its 

 course. 



Ice-sheet here less exten- 

 sive than in the first Glacial 

 epoch, and not generally bor- 

 dered as then by lakes in val- 

 leys which now drain south- 

 ward. 



Terminal moraines at ex- 

 treme limit of the ice-ad- 

 vance, and at ten or more 

 stages of halt or readvance 

 in its retreat. 



Depression probably al- 

 most to the present level. 

 Restoration of arid climate ; 

 nearly or quite complete 

 evaporation of Lakes Bonne- 

 ville and Lahontan. Forma- 

 tion of the "adobe" con- 

 tinuing through the second 

 Glacial, Champlain, and Re- 

 cent epochs. 



Probable uplift 3,000 feet, 

 shown by submerged valleys 

 near Cape Mendocino. Sec- 

 ond ice-sheet on British Co- 

 lumbia and Vancouver Island ; 

 local glaciation of Rocky 

 Mountains, Cascade range, 

 and Sierra Nevada, south~to 

 latitude 37°. First great rise 

 of Lakes Bonneville and La- 

 hontan. 



Final departure of the ice- 

 sheets ; glacial rivers form- 

 ing eskers and kames. Loess 

 deposited while the reeion of 

 the Alps was depressed lower 

 than now. Upper (englacial) 

 till, and asar, of Sweden. 

 Marine submergence 500 to 

 600 feet in Scotland, Scandi- 

 navia, and Spitzbergen. 



Depression nearly to pres-j 

 ent level southward; morej 

 northward, but followed there, 

 by differential uplift of 800 or! 

 1,000 feet. Great erosion of 

 loess and other modified drift, 

 and of " Orange Sand." Val- 

 leys of this epoch, partly 

 filled with later till, are 

 marked by chains of lakes in 

 southern Minnesota. 



Pliocene elevation of con- 

 tinent brought to culmination 

 at beginning of Quaternary 

 era ; this whole basin proba- 

 bly then uplifted 3.000 feet ; 

 excessive snowfall and rain ; 

 deposition of the "Orange 

 Sand." Ice-gheet south to 

 Cincinnati and St. Louis, at 

 length depressing the earth's 

 crust beneath it ; slackened 

 river floods and shallow lakes, 

 forming the loess. 



Continental depression. Ar- 

 id climate. Long-continued 

 denudation of the mountains: 

 resulting very thick subaerial 

 deposits of the "adobe." 



Intermittent volcanic ac- 

 tion in various parts of this 

 region, throughout the Qua- 

 ternary era to very recent 

 times, and liable to break 

 forth arain. 



Second elevation and gen- 

 eral glaciation of northwest- 

 ern Europe; the ice-sheets of 

 Great Britain probably more 

 extensive than in first Glacial 

 epoch. Oscillations of ice- 

 front ; British Lower and 

 Upper bowlder - clays, the 

 Chalky, Purple, and Hessle 

 bowlder-clays. Terminal mo- 

 raines in Germany. 



Latest rise (3.000 feet) of 

 ithe Colorado Canon district. 

 I Sierra Nevada and other 

 jGreat Basin mountain-ranges 

 [formed by immense uplifts, 

 twith faulting. California riv- 

 er-courses changed ; human 

 bones and implements in the 

 old river gravels, lava-cov- 

 lered. Ice-sheet on British Co- 

 lumbia; local glaciers south- 

 ward. 



i 



Recession, orprobablyeom- 

 plete departure, of the ice- 

 sheets. 



Land connection between 

 Europe and Africa, permit- 

 ting southern animals to ex- 

 tend far northward. 



Erosion of the Somme Val- 

 ley below its oldest imple- 

 ment-bearing gravels. 



Uplift and glaciation of 

 northwestern Europe: maxi- 

 mum elevation. 2.500 feet or 

 more (depth of the Skager 

 Rack) ; France and Britain 

 united with the FarOe Isl- 

 ands, Iceland, and Green- 

 land. Uplifts of the Hima- 

 layas and other mountain- 

 ranges attendant on both 

 Glacial epochs. 



