Keywords: The Quarterly journal of the Geological Society of London (12895285164).jpg 1864 <br> HIND GLACIAL DRIFT <br> 129 <br> § 6 Parallelism of Escarpments in America <br> In 1860 I described the remarkable paral- <br> lelism which exists between great escarpments <br> in America north of the 40th parallel of latitude <br> 1st The Niagara escarpment <br> 2nd The Riding Duck and Porcupine Hill <br> escarpment west of Lake Winnipeg <br> 3rd The escarpment of the Grand Coteau <br> de Missouri <br> These are all roughly parallel to one another <br> and are many hundred miles in length The <br> lowest the Niagara varies from 600 feet to <br> 1300 feet above the sea ; the second west of <br> Lake Winnipeg from 1600 feet to 2000 ; the <br> third the Grand Coteau de Missouri from 2000 <br> to 3000 feet and more above the ocean see <br> fig 3 They have all easterly north-easterly <br> or northerly aspects in relatively different parts <br> of their lengths f and appear to have a com- <br> mon origin If it can be shown conclusively <br> as Mr Whitney believes that the driftless <br> area in Wisconsin has never been overflowed <br> these escarpments as well as those of their <br> great outliers in the far West can only be <br> due to the same agent which excavated the <br> basins of the great American lakes <br> The symmetrical escarpments of the Grand <br> Coteau de Missouri the Riding Mountain and <br> its prolongations and portions of the Niagara <br> escarpments are probably the result to a large <br> extent of the action of glacial rivers under- <br> mining and washing away the soft strata of <br> the sedimentary rocks and excavating in ad- <br> vance of the glacial mass itself; and they re- <br> present different and closely succeeding gla- <br> cial periods the Missouri escarpment being <br> older than that of the Riding Mountain with <br> however a distinct geological interval between <br> them The close proximity of the isothermal <br> curves in these latitudes to the general direc- <br> tion of the escarpments of the Grand Coteau <br> and Riding Mountain is a very interesting <br> and important feature in connexion with the <br> cause which produced them <br> See my ' Narrative of the Canadian Exploring <br> Expeditions of 1857 and 1858 ' vol ii p 266 for a <br> notice of these escarpments <br> t The western exception at Cypres Hills has been <br> already noticed Here the flanks of the Rocky Moun- <br> tains are approached <br> VOL XX PART I <br> T H <br> £ <br> J <br> – oo - <br> 2 36089370 111261 51125 Page 129 Text v 20 http //www biodiversitylibrary org/page/36089370 1864 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 20 1864 Geology Periodicals Smithsonian Libraries bhl page 36089370 dc identifier http //biodiversitylibrary org/page/36089370 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-03 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12895285164 2015-08-26 16 58 02 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1864 Photos uploaded from Flickr by Fæ using a script |