Jökulhlaup-related Ice Fracture and Supraglacial Water Release During the November 1996 Jökulhlaup, Skeiðarárjökull, Iceland

During the initial stages of the November 1996 jökulhlaup at Skeiðarárjökull, Iceland, floodwaters burst onto the glacier surface via a series of fractures. This supraglacial drainage led to the formation of a number of distinct ice surface depressions, one of which is investigated in detail. The morphology and structural characteristics of this feature are described, as well as the sedimentology of an associated assemblage of debris-filled fractures. This work suggests that debris-charged subglacial floodwaters travelled up to the glacier surface, where supraglacial flow occurred initially via an extensive network of fractures, orientated parallel to the glacier margin. Supraglacial discharge became progressively more focused into a series of discrete outlets, leading to the mechanical erosion of a number of depressions on the glacier surface. The associated transfer of subglacially derived floodwaters to high levels within the glacier resulted in the rapid entrainment of large volumes of sediment which may influence the patterns, processes and products of ice-marginal sedimentation in the future.     

Books,Atlases, & Maps Received

Abstract

R. Warwidk Armstrong, Editor and Project Director. ATLAS OF HAWAII. The University Press of Hawaii, Department of Geography, University of Hawaii, Honolulu, 1973. 222 pages. Paper cover, $15.00.

Bernadine Bailey. GREENLAND IN PICTURES. Visual Geography Series, Sterling Publishing Company, Inc., New York, 1973. 64 pages. Paperback, $1.25.

Yi-Fu Tuan. TOPOPHILIA: A Study of Environmental Perception, Attitudes and Values. Prentice-Hall, Inc., Englewood Cliffs, New Jersey 07632, 260 pages. Cloth cover, $8.95, paper cover, $4.95.

Merrill M. Stuart. MASTER'S THESES IN GEOGRAPHY: AMERICAN AND CANADIAN UNIVERSITIES. Geographic and Area Study Publications, Tualatin, Oregon, 1973. 275 pages, Library bound $11.00, Paper back $7.00.

R. J. Johnston. SPATIAL STRUCTURES: Introducing the study of spatial systems in human geography. St. Martin's Press, New York, 7973. The Field of Geography. 137 pages. Cloth cover, $6.95.

Charles ReVelle, Penelope ReVelle. SOURCEBOOK ON THE ENVIRONMENT: The Scientific Perspective. Houghton Mifflin Company, Boston, Mass. 02107, 1974. 332 pages. Paper back, N.P.

Raymond E. Crist, Charles M. Nissly. EAST FROM THE ANDES: Pioneer Settlements in the South American Heartland. University of Florida Press, Gainesville, Florida, 1974. 166 pages, Paper cover, $4.00.

Edited with an introduction by Louis H. Masotti and Jeffrey K. Hadden. SUBURBIA IN TRANSITION. New Viewpoints -A Division of Franklin Watts, Inc., New York, 1974. 345 pages. Paper back, $4.95.

Gordon Oosterman. THE PEOPLE: Three Indian Tribes of the Southwest. The National Union of Christian Schools, William 6. Eerdmans Publishing Company, Grand Rapids, Michigan, 1973. 117 pages. Paper, $2.45.

Spencer D. Parker. GHANA. Bellhaven House, Scarborough 707, Ontario, Canada, 1973. 96 pages. Paper, $3.95.

Chryssee MacCasler Perry Martin and Esmond Bradley Martin. QUEST FOR THE PAST: An Historical Guide to The Lamu Archipelago. Marketing and Publishing Ltd., 1973. 32 pages. Paper, N. P.     

Books,Atlases, & Maps Received

Abstract

Alan R. H. Baker, John D. Hamshere, John Langton (eds.). GEOGRAPHICAL INTERPRETATIONS OF HISTORICAL SOURCES. New York: Barnes & Noble, 1970. Preface, index, maps. 452 pages. Cloth, $13.00.

Amry Vandenbosch. SOUTH AFRICA AND THE WORLD. Lexington: The University Kentucky Press, 1970. Preface, table of contents, index. 301 pages. Cloth, $8.50.

World Book Science Annual. SCIENCE YEAR 1971 Chicago: Field Enterprises Educational Corporation, 1970. Preface, table of contents, index, diagrams, photographs (many in color). 442 pages. Cloth, n.p.

Wilbur Zelinsky, Leszek A. Kosinski, R. Man-sell Prothero (eds.). GEOGRAPHY AND A CROWDING WORLD. New York: Oxford University Press, 1970. Preface, introduction, epilogue, glossary, index, tables and maps, bibliographies. 601 pages. Cloth, $10.95.     

Sea‐level and ocean‐current control on carbonate‐platform growth,Maldives, Indian Ocean

Multichannel high‐resolution seismic and multibeam data were acquired from the Maldives‐isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform evolution, with a special emphasis on sea‐level changes and changes of the oceanic currents. The stacking pattern of Lower to Middle Miocene depositional sequences, with an evolution of a ramp geometry to a flat‐topped platform, reflects variations of accommodation, which here are proposed to be primarily governed by fluctuations of relative sea level. Easterly currents during this stage of bank growth controlled an asymmetric east‐directed progradation of the bank edge. During the late middle Miocene, this system was replaced by a twofold configuration of bank development. Bank growth continued synchronously with partial bank demise and associated sediment‐drift deposition. This turnover is attributed to the onset and/or intensification of the Indian monsoon and related upwelling and occurrence of currents, locally changing environmental conditions and impinging upon the carbonate system. Mega spill over lobes, shaped by reversing currents, formed as large‐scale prograding complexes, which have previously been interpreted as deposits formed during a forced regression. On a regional scale, a complex carbonate‐platform growth can occur, with a coexistence of bank‐margin progradation and aggradation, as well as partial drowning. It is further shown that a downward shift of clinoforms and offlapping geometries in carbonate platforms are not necessarily indicative for a sea‐level driven forced regression. Findings are expected to be applicable to other examples of Cenozoic platforms in the Indo‐Pacific region.     

Landscape Photography,Geographic Education,and Nation‐Building In Democratic Kampuchea, 1975–1979

On April 17, 1975, Phnom Penh, the capital of Cambodia, fell to the armed forces of the Communist Party of Kampuchea (CPK). Cambodia, however, was not primed for revolution. This is significant in that it contributed to specific postconflict policies and programs initiated by the CPK, including the promotion of geographic education and the use of propaganda photographs. In this article we examine six photographs produced during the Khmer Rouge era. Our main thesis is that when viewing these photographs, we are witnessing the photographic production of a nationalist landscape. As geographers have argued, photographs are inauthentic from the standpoint of “truthful” representations. However, the photographs produced by the CPK are authentic simulacra in their “truthful” representation of how the CPK envisioned both the revolution and subsequent administration of Democratic Kampuchea. In so doing, our research is positioned within a longer tradition of cultural‐political geography that has examined the use of landscape photographs as political instruments used in nation‐building.     

Recurring Jökulhlaups in Sälka, Northern Sweden

An ice‐dammed lake at the margin of the glacier Sälkaglaciären, in the Kebnekaise Mountains in northern Sweden, drained suddenly in July 2003 producing a flood with a measured peak discharge of 9.5±0.25 m³s^‐1. The total lake volume of 4.55×10⁵ million³ drained within two days. The hydrograph of this event is characteristic of a jökulhlaup controlled by a single basal ice tunnel that enlarges due to melting. The jökulhlaup had an exponential rise to a peak discharge, and following the peak, a very steep fall in discharge as the water supply to the drainage system ceased. A similar jökulhlaup was observed in August 1990 with an estimated release of 8.05×10⁵ m³ water. Jökulhlaups at Sälkaglaciären are recurring events and have been indirectly observed since the 1950s.     

Late Ordovician,deep‐water gravity‐flow deposits,palaeogeography and tectonic setting,Tarim Basin,Northwest China

The Upper Ordovician in the Tarim Basin contains 5000–7000 m of siliciclastic and calciclastic deep‐water, gravity‐flow deposits. Their depositional architecture and palaeogeographical setting are documented in this investigation based on an integrated analysis of seismic, borehole and outcrop data. Six gravity‐flow depositional–palaeogeomorphological elements have been identified as follows: submarine canyon or deeply incised channels, broad and shallow erosional channels, erosional–depositional channel and levee–overbank complexes, frontal splays‐lobes and nonchannelized sheets, calciclastic lower slope fans and channel lobes or sheets, and debris‐flow complexes. Gravity‐flow deposits of the Sangtamu and Tierekeawati formations comprise a regional transgressive‐regressive megacycle, which can be further classified into six sequences bounded by unconformities and their correlative conformities. A series of incised valleys or canyons and erosional–depositional channels are identifiable along the major sequence boundaries which might have been formed as the result of global sea‐level falls. The depositional architecture of sequences varies from the upper slope to abyssal basin plain. Palaeogeographical patterns and distribution of the gravity‐flow deposits in the basin can be related to the change in tectonic setting from a passive continental margin in the Cambrian and Early to Middle Ordovician to a retroarc foreland setting in the Late Ordovician. More than 3000 m of siliciclastic submarine‐fan deposits accumulated in south‐eastern Tangguzibasi and north‐eastern Manjiaer depressions. Sedimentary units thin onto intrabasinal palaeotopographical highs of forebulge origin and thicken into backbulge depocentres. Sediments were sourced predominantly from arc terranes in the south‐east and the north‐east. Slide and mass‐transport complexes and a series of debris‐flow and turbidite deposits developed along the toes of unstable slopes on the margins of the deep‐water basins. Turbidite sandstones of channel‐fill and frontal‐splay origin and turbidite lobes comprise potential stratigraphic hydrocarbon reservoirs in the basin.     

American Migration,Settlement, and “Belonging” in Francophone Canada

More Americans now reside in Canada than at any time since the Vietnam War. Of particular note is the surprisingly large population of immigrants from the United States who now reside in Montreal—Francophone Canada's largest and most diverse city. This article documents and analyzes the migration experiences, spatial patterns, and “sense of belonging” of Americans in Montreal during the post–Vietnam era framed within the larger political and linguistic context of the city's “Two Solitudes.” Findings are based on information compiled from archival materials, census records, structured and unstructured interviews, survey questionnaires, participant observation, and fieldwork. My overarching goal is to embed the experiences and patterns of this English‐speaking group of immigrants in predominately French‐speaking Montreal during the past five decades—one of the most dramatic and divisive periods of time in Montreal and in Quebec as a whole.     

Malariological and sociological significance of ‘tanka’ and ‘beri’ in the Thar Desert, Western Rajasthan, India

Both ‘tanka’ and ‘beri’, the well-like structures made for storing drinking water fetched from distant places or superficially charged from the runoff water of the monsoon rains, are considered integral components of rural communities in the Thar Desert of Rajasthan State in north-western India.A. stephensi, the confirmed malaria vector in desert regions, breeds in these structures predominantly.     

Topography of a composite relict rock glacier, Ślęża Massif, SW Poland

A detailed geodetic survey and, additionally, a map of slope covers have been carried out for a composite relict rock glacier on the slopes of Mt ?l??a (718 m a.s.l.), Sudetic Foreland, SW Poland. The survey allows one to distinguish the mobilisation, transition and accumulation zones and to define geomorphic features diagnostic for relict rock glaciers such as lateral ridges standing above a central depression, steep margins of the landforms in the transition and accumulation zones, as well as absence of distinct head scarps above. Furthermore, it indicates that the present‐day hydrographic pattern on the surface of relict rock glaciers has been superimposed on the relief inherited from the active landforms. The topography indicates that tension prevailed rather than compression during the development of the rock glaciers. Some of the features, such as small lateral lobes, developed probably as a result of the compressive flow, however. The pattern of the slope cover shows that it developed during activity of the rock glaciers and been modified afterwards due to solifluction.