Ice Dam Research Articles

What are glacier surges?

A total of 204 surging glaciers has been identified in western North America. These glaciers surge repeatedly and probably with uniform periods (from about 15 to greater than 100 years). Ice flow rates during the active phase may range from about 150 m/year to > 6 km/year, and horizontal displacements may range from < 1 to > 11 km. Ice reservoir and ice receiving areas can be defined for surging glaciers, and the reservoir area does not necessarily coincide with the accumulation area. Glaciers of all shapes, sizes, and longitudinal profiles can surge, and no unusual "ice dams" or bedrock constrictions are evident. Surges occur in many different climatic, tectonic, and geologic environments, but only in certain limited areas (mainly in the Alaska, eastern Wrangell, and St. Elias mountains). Three types of surging glaciers are defined: (I) large to moderate-sized glaciers with large displacements and very fast flow, (II) large to moderate glaciers with moderate displacements and flow rates, and (III) small glaciers with small displacements and moderate to fast flow rates. All three types involve an inherent instability which is self-triggered at regular intervals, but with Type I surges an additional (unknown) mechanism produces the very high flow rates.

The ice-dam, powder-flow theory of glacier surges

In this theory it is assumed that a stagnant ice block or dam develops in the lower regions of a glacier. Ice gradually builds up above the dam while the dam itself becomes thinner by ablation. Eventually the upper end of the stagnant ice block crumbles from the force of the ice above it, and much of the glacier is changed from a state of compression to one of tension. The breaking of the ice dam results in the glacier rapidly becoming broken into a mass of blocks or powdered ice. The apparent viscosity of the broken-up glacier is much less than that of bulk ice, so high velocities of flow are possible, and a phenomenon similar to a mud flow results. This theory explains why some glaciers repeatedly surge yet appear stagnant between surges. The broken-up appearance of surging glaciers and the delayed surging of tributaries are explained. Additional substantiating observations on several of these phenomena are presented.

Some Hypotheses on Surging Glaciers

Glacier surges can result when an ice dam, which is above the equilibrium length of the glacier, breaks from the forces of the excess ice that builds up behind the dam. It is shown that the high velocities of flow of surging glaciers cannot be due to the normal pseudo-plastic flow of glacier ice. Rather, the high velocities must result from a combination of sliding on the glacier bed and a fluidized block (or powder) flow resulting from melt water around the ice blocks in the interior and at the base of the ice mass. Various calculations are made to show the feasibility of the mechanisms proposed. The predictions are in line with the available observations on surging glaciers.

Glacier Dammed Lakes in Norway

Glacier dammed lakes may have their outflow over a bedrock threshold like other lakes, or they may flow on the surface or below the damming ice. In the former case the lake, over some considerable period, has a constant maximum level with marked shore lines corresponding to the threshold. But when the level is determined by the ice dam, the conditions are unstable. The level of the lake will then to a certain extent vary in step with the glacier, and never remain at a certain level for any length of time. The normal behaviour of such a lake will be a moderately fast rise of the water level, dependent upon the supply, until a certain critical level is reached, whereupon drainage is rapid. Such is also to some extent the case with the type of lake first mentioned, if the height of the pass is situated near to the critical level for drainage.

EXTENSION OF TAZEWELL GLACIAL SUBSTAGE OF WESTERN ILLINOIS INTO EASTERN IOWA

Research Article| May 01, 1954 EXTENSION OF TAZEWELL GLACIAL SUBSTAGE OF WESTERN ILLINOIS INTO EASTERN IOWA PAUL R SHAFFER PAUL R SHAFFER UNIVERSITY OF ILLINOIS, URBANA, ILLINOIS Search for other works by this author on: GSW Google Scholar Author and Article Information PAUL R SHAFFER UNIVERSITY OF ILLINOIS, URBANA, ILLINOIS Publisher: Geological Society of America Received: 06 Aug 1953 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1954, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1954) 65 (5): 443–456. https://doi.org/10.1130/0016-7606(1954)65[443:EOTGSO]2.0.CO;2 Article history Received: 06 Aug 1953 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation PAUL R SHAFFER; EXTENSION OF TAZEWELL GLACIAL SUBSTAGE OF WESTERN ILLINOIS INTO EASTERN IOWA. GSA Bulletin 1954;; 65 (5): 443–456. doi: https://doi.org/10.1130/0016-7606(1954)65[443:EOTGSO]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 Green River lobe of Tazewell (Shelbyville) ice extended west of the Mississippi River to the eastern border of the Goose Lake Channel in Clinton County, Iowa. It extended northwestward to within 1½ miles of the village of Goose Lake, across an area previously mapped as Iowan and Kansan drift. A small area of Illinoian drift is present between the Shelbyville drift and the Goose Lake Channel.The Iowan drift is separated from the western border of the Goose Lake Channel and the Shelbyville drift by a small strip of Kansan drift on the north and a small area of Illinoian drift on the south.When the Shelbyville ice reached the “big bend” of the Illinois River in Bureau County, Illinois, it blocked the eastward-flowing drainage of the old Mississippi River and formed the first stage of glacial Lake Milan which extended from the “big bend” to the rock-defended outlet near Andalusia, Illinois. Later when the Shelbyville ice had advanced westward to the west side of the present Rock River valley, glacial Lake Milan was restricted to the lower Rock River valley, and glacial Lake Cordova formed north and northwest of the ice dam. The outlet for glacial Lake Cordova was over a divide composed of Illinoian drift between Cordova, Illinois, and Le Claire, Iowa. Later when the Shelbyville ice crossed the present Mississippi River valley, glacial Lake Savanna was formed to the north. Its waters rose until they found an outlet through the Goose Lake Channel to the Wapsipinicon River, down the Wapsipinicon and through the new valley past Cordova and Le Claire. When the Shelbyville ice withdrew, the present course of the Mississippi River between Fulton, Illinois, and Keokuk, Iowa, had been established.Two sets of loess-covered terrace remnants, deposited under different controlling conditions, are present between Geneseo and Lomax, Illinois. One set between Geneseo and Andalusia, Illinois, rises to a nearly uniform height and resulted from quiet-water deposition in glacial Lake Milan. Below Muscatine, Iowa, lie remnants of deposits made up largely of fine sands and silts, whose deposition was controlled by a constriction in the valley of the Mississippi River near Keokuk. When the great volume of water from the upper Mississippi drainage was added to that already flowing past Keokuk, constriction caused higher water levels upstream with areas of relatively quiet water in marginal portions of the valley and in the ponded tributaries.The possible contemporaneity of the Shelbyville terrace on the lower Iowa with the high terrace of Lake Calvin upstream calls for a re-examination of the terraces along the Iowa River and raises the question of the possibility that the Shelbyville and the Iowan were contemporaneous. 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.

Unusual currents in Glacial Lake Missoula, Montana

The area submerged by Glacial Lake Missoula includes several intermontane basins and constricted interconnecting valleys or “narrows” that drain to a single outlet, the Clark Fork River. A sudden failure of the ice dam that blocked this valley, near the Idaho-Montana State line, caused unusually large and rapid currents through the narrows and wind gaps in the partly submerged rim of Camas Prairie basin. Evidences of such currents include commensurate, but otherwise ordinary, effects of streams confined to rocky channels and the unique giant ripple marks. At its high stage the lake is roughly estimated to have held more than 500 cubic miles of water of which nearly three-fourths was stored above a constricted part of the Clark Fork Valley called the Eddy Narrows. Calculations based on available incomplete data indicate a flow through the Eddy Narrows that reached a maximum of 9.46 cubic miles per hour. Whether the lake was completely drained at that time has not been determined, but a later set of beaches testifies that the basin held a lake soon after the rapid outflow. Apparently the final draining was gradual.

Shyok Glaciers and Indus Floods

UNDER the above title, Mr. J. M. Lacey in an article in the Engineer for October 14 gives an account of the formation of the great ice dams which form across the Upper Shyok River in Kashmir, and of the floods in the Indus valley which result from the release of the large volumes of water pent up behind the dams. The Upper Shyok has its source in the Rima Glacier in the Karakoram region, and in its downward course passes the three important glaciers, Chong Kumdan, 9 miles long, falling 3,000 ft.; the Kichik Kumdan, 7 miles long, falling 3,500 ft.; and the Aktash, 5 miles long, falling 2,000 ft. In the event of heavy accumulation of snow on the eastern range, these glaciers advance rapidly into the Shyok gorge. On occasions they flow right across the river until they strike the precipitous cliffs on the opposite side, and sometimes turn down the bed of the river for hundreds of yards. The first recorded damming of the Shy ok occurred in 1779, the water breaking through and causing a flood the following year. Since then the river has been dammed many times but experts find great difficulty in forming any conclusion regarding the periodicity of the advance and retreat of the glaciers. One observer, Major Mason, however, considers that after 1932 there will be no danger of a block for another thirty years.