Upham, Warren

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Journal of the Minnesota Academy of Science Volume 4 Number 3 Article 11 1910 Englacial and Superglacial Drift in Minnesota, the Dakotas, and Manitoba Warren Upham Follow this and additional works at: https://digitalcommons.morris.umn.edu/jmas  Part of the Glaciology Commons Recommended Citation Upham, W. (1910). Englacial and Superglacial Drift in Minnesota, the Dakotas, and Manitoba. Journal of the Minnesota Academy of Science, Vol. 4 No.3, 428-429. Retrieved from https://digitalcommons.morris.umn.edu/jmas/vol4/iss3/11 This Article is brought to you for free and open access by the Journals at University of Minnesota Morris Digital Well. It has been accepted for inclusion in Journal of the Minnesota Academy of Science by an authorized editor of University of Minnesota Morris Digital Well. For more information, please contact skulann@morris.umn.edu. ENGLACIAL AND SUPERGLACIAL DRIFT lA MINNESOTA, THE DAKOTAS, AND MANITOBA. By Warren Upham, D. Sc., St. Paul, Minn. [Abstract of a paper read before the Minnesota Academy ot Sciences, December 7, 1909.] Modified drift, consisting of stratified gravel and sand, with local deposits of clay, overlles the bed-rocks and the Ull, and generally forms the surface, on an extensive area stretching from St. Paul and Mln-ceapolls northwestward to the lakes at the sources of the Mlsstsstppl, and onward to the Rainy river, the southwest side of the Lake of the Woods, and to the vicinity of the city of Winnipeg.· The contour of the greater part of these deposits, through their extent of 400 miles, is flat or moderately undulating, and their surface varies In height from a few feet to 50 feet or rarely more above the adjoining lakes and streams. In central Minnesota these tracts of gravel and sand have nn elevation that increases from south to north, being 825 to 950 feet above sea level near the Twin Cities, rising gr..adually to 1,200 feet tn the distance of about 100 miles northwest to Brainerd, and ranging from 1,350 to 1,500 feet between the Leaf hills and Itasca lake. Thence their surface s inks to 1,150 to 1,075 teet in the vicinity of Rainy river and the Lake of the Woods, and is between 760 and 875 feet in the district close northeast of W innipeg, where a part of these deposits forms a remarkable €sker, named Bird's Hill. On each side this broad belt is bordered by areas of nearly the ~:;ame general elevation, which have mostly a surface of till ; and It it~ to be remarked that the heights of the t racts of modified drlft and till are alike determined by that o( the underlying rocks, on which these superficial deposits are spread in a sheet of slight depth in comparison with the gradual change in thei r elevation. The drift sheet on this belt, Including both the sand and gravel and the till, probably varies tn Its average thickness from 60 to 150 feet, whUe Its central portion rises •oo to 600 teet above its south and north ends. The dfstribuUon of the modified drift thus found upon large tracts along a wide belt from St. Paul to Winnipeg, while it is more scan tily developed on a still wider region of Minnesota, South and · North Dakota, and Manitoba, southwest of thl:o belt . and ltkewl.se Is !!canty or wanthlg on its northeast side in northern Minnesota and about Rainy lake and the northeast and north por tions of the Lake ot the Woods, seems to be attributable to converging slopes of the sur-face of the lee-sheet and the consequent convergence of its currents, which brough t an unusual amount of englaclal drift Into the ice along this belt, nnd by wbtch also the streams produ~ed tn Its melting were caused to ftow thither from extensive tracts of the Ice on the east and west. The glacial striae of these adjoining areas show that on the east the course of the motion and the descent of the surface ot the tee-sheet were trom northeast to southwest, but that on the west the D1g1t1z a by Coogle E11glatial a11d S uf't'rglociol Drif t glacial cu r rents moved and the lee surfnce sloped toward the south-Pas t. My studies of the prominent. kame called the Oevlrs Heart hill,• on the so nth s ide of Devll's lake in North Da kola, and of Blrd's H ill,t nea r Winnipeg, convince me that much drift wac& carried upwa rd into • t.he Ice-sheet of this region, to heights of 1,000 to 1,600 feet or more above t.he g round. The distan.::e f rom Bird's Hill to the boundary of the glacial drltt Is about 700 miles to the sou th and 300 mtles to the south-Wt>st. 1t rna:)>· be estimated, from altitudes of the d rift on the White rr.oun tlllns, the Catskills, and ihe Adirondacks, that the tee-sheet slml· la rly r is ing oYer ~tanltoba atialned a maximum t.hicknei!S of at least one mile, or more probably one and a half mnes, about 8,000 feet. The gTadlents of its surface were similar to the s lowly ascending slopes by which the Ice-sheets of Greenland and the Antarct.lc conli· nen t r ise to altitudes of about two miles above the sea. In the lower quarter or sl.xth part of the Ice coverlng .Manitoba, that is, to a height of probably J ,500 feet, much drlrt had been carried by its variable and par tly rising curr ents. Ne.ar the border of the Ice-sheet. during its time of accumulation, little drift could thus be carried lnto It, and t herefore in the melting and recession oC that outer part t he englactal and ftnally super-glacial drift was generally Inconspicuous; but at any considerable <U.s· tance Inside the glaciated area as a score of miles or, more. the ftnal melting set free much fonnerly englaclal t lll and modified drtfL The processes or drift transportation and depos ition here empha· sized were well stated by Prot. N. H . Winchell In 1873.• b:r Prot. C. H. Hitchcock In 1878,t and by me In 1876 and 1878 and In numerous later papers and reports.t At tbe presen t day these processes are exemplified by the :Malaspina glacier or piedmont lc~sheet in Alaska, which du ring t he last century has been much reduced in area and thickness ; but th e Greenland and Antarctic tee-sheets, . which are now constant or Increas ing by snowfall, have no superglaclal drift . ,. The Glacial L uk e .Agalll!U , U. S. G£-ol. Survey, Monograph XXV, 1895. pp. 156. 157. t Tbld .. pp. 183-188: nl!<O n pn per p r cs f'ntcd to t he Geologlc~l l::oclety of Amt>rku. December , 1909. vol. XXI, pp. ~Oi- 4 :1:!. • 111e Drift Deposits o f the Northwest. Popular Sc:<>nce Mon thly, v ol. H I, p !). !!02-210. 38£-:!97 (esp.eclally page 29t. rela t ing to eupergla.clal drift). t Gt>olog)' ot New Hampshlr~. vol . ITI. pp. !!82. 283, 309, 326, 333-8. t P roc. A . A . A . S . • vol. XX\?, for 1876, p . 2JS; vol. XXVII, for 1878, pp. 299-310. Geol of N . H .• v ol Il l. ISiS, pp. 9, 10, 175-G. 286-309. Geol. ot )t tnnt>sotn. FfrinJ ,R fl port, vol. I , l SU. pp. 440, 603- 4 ; voh U. 1888, pp. :!52, 254·6. 409-41 7. Am. Gt>ulog!::t, \'ti l. X , 18!12, pp. S39-362: v ol. XII, 1893, pp. 36-U; vol. XIV, 189.- . pp. 69-83 : vol. XV I, 1896, pp. 100-113: vol. XIX, 1897, pp. 411-417 ; vol. XX. 1897, p p. 383-7: vol. XXUl, 1899, pp. 369-314 ; vol. XXV, 1 900, pp, 27 3-299. Dtgtttz a by Coogle 

Englacial and Superglacial Drift in Minnesota, the Dakotas, and Manitoba

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Englacial and Superglacial Drift in Minnesota, the Dakotas, and Manitoba

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