Esker characteristics in terms of glacier physics, Katahdin esker system, Maine

Research Article| May 01, 1985 Esker characteristics in terms of glacier physics, Katahdin esker system, Maine RONALD L. SHREVE RONALD L. SHREVE 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024 Search for other works by this author on: GSW Google Scholar Author and Article Information RONALD L. SHREVE 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1985) 96 (5): 639–646. https://doi.org/10.1130/0016-7606(1985)96<639:ECITOG>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RONALD L. SHREVE; Esker characteristics in terms of glacier physics, Katahdin esker system, Maine. GSA Bulletin 1985;; 96 (5): 639–646. doi: https://doi.org/10.1130/0016-7606(1985)96<639:ECITOG>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The characteristics of large, subglacially formed eskers, such as the Katahdin system, are closely related to two special peculiarities of water-filled tunnels along the beds of ice sheets: (1) the water pressure approximates the weight of the overlying ice; and (2) in tunnels that descend and those that ascend less steeply than ∼1.7 times the ice-surface gradient, the walls melt, producing a sharply arched tunnel cross section, whereas in those that ascend more steeply, they freeze, producing a wide, low one. The first peculiarity primarily governs the paths of these eskers. It causes the tunnels to follow the paths ordinary rivers would follow were the land tipped downglacier ∼11 times the local ice-surface gradient. The paths therefore trend in the general direction of the former ice flow but tend to deviate so as to follow valleys and to cross divides at the lowest passes, as observed. Ice-surface gradients calculated from path deviations at two localities on the Katahdin esker system indicate relatively thin, sluggish ice the surface of which lay ∼200 m below the summit of Mount Katahdin, in agreement with independent geologic evidence. The second peculiarity primarily governs the form, composition, and structure of these eskers. Strong melting causes a large inflow of basal ice and entrained debris to the tunnel and produces sharp-crested eskers of poorly sorted, poorly bedded sand, gravel, and boulders with lithologies like the adjacent till, whereas weaker melting produces multiple-crested ones of similar composition. Freezing precludes inflow and produces broad-crested eskers of fairly well-sorted, well-bedded, more water-worn, coarse sand with few large clasts. Ice-surface gradients calculated from transitions from the multiple-crested type to small areas of broad-crested type on the Katahdin system agree closely with those computed from the paths at nearby localities. An anomalously low gradient calculated from a transition to an area of broad-crested type approximately twice as wide and long as the probable ice depth apparently confirms that, as expected, the basal ice was supported by water pressure over most, if not all, of the width of the esker. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.