The Experts below are selected from a list of 36345 Experts worldwide ranked by ideXlab platform
James L Wescoat - One of the best experts on this subject based on the ideXlab platform.
-
human use of Landforms on the deccan volcanic plateau formation of a geocultural region
Geomorphology, 2019Co-Authors: James L WescoatAbstract:Abstract This paper takes its inspiration from Karl W. Butzer's course on the Human Use of Landforms at the University of Chicago. It builds upon that concept through an exploration of regional settlement patterns and Landforms in the Deccan volcanic province of west-central India. The first section develops a conceptual framework for analyzing human adjustment to Landforms on regional, settlement, and site scales. The second section employs that framework to analyze four major landform-settlement configurations in the Deccan from antiquity to the end of the eighteenth century. The Satavahana kingdom (ca. 100 BCE to 200 CE) had a strong southeast to northwest alignment along the Godavari River. Their capital city of Paithan was located at a navigable sacred ford across the river (tirtha), which was linked with upstream confluences (sangams), tanks (kunds), mountain passes (ghats), and port cities on the Arabian Sea. Subsequent Hindu dynasties (ca. 850–1300 CE) shifted from fluvial Landforms to a north-south alignment along steep mesa escarpments and buttes in the central Deccan that provided defensive fortress and cave temple sites. Sultanate and Mughal forces expanded the urban footprint on nearby plateau lands at sites protected by surrounding mesas (ca. 1330–1700 CE). These cities were supported by local watershed runoff and long distance water channels. The final precolonial phase of Deccan settlement entailed a shift from the semiarid central plateaus to humid headwaters of the Western Ghats, whose buttes and scarps provided sites for scores of forts controlled by the founder of the Maratha empire Chhatrapati Shivaji in the seventeenth century. Maratha success led to development downstream at the capital city of Pune (1627–1803 CE), located at a river confluence flanked by mesas, which combined the strategies of previous periods. Over two millennia these four distinct, yet intersecting, patterns of human-landform relations have shaped an evolving geocultural region on the Deccan plateau that deserves comparison with other flood basalt regions.
Sasan Aleebrahim - One of the best experts on this subject based on the ideXlab platform.
-
landform classification from a digital elevation model and satellite imagery
Geomorphology, 2008Co-Authors: Hossein Saadat, Robert Bonnell, F Sharifi, G R Mehuys, Mohammad Namdar, Sasan AleebrahimAbstract:The Iranian Soil and Water Research Institute has been involved in mapping the soils of Iran and classifying Landforms for the last 60 years. However, the accuracy of traditional landform maps is very low (about 55%). To date, aerial photographs and topographic maps have been used for landform classification studies. The principal objective of this research is to propose a quantitative approach for landform classification based on a 10-m resolution digital elevation model (DEM) and some use of an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image. In order to extract and identify the various Landforms, slope, elevation range, and stream network pattern were used as basic identifying parameters. These are extractable from a DEM. Further, ASTER images were required to identify the general outline shape of a landform type and the presence or absence of gravel. This study encompassed a relatively large watershed of 451 183 ha with a total elevation difference of 2445 m and a variety of Landforms from flat River Alluvial Plains to steep mountains. Classification accuracy ranged from 91.8 to 99.6% with an average of 96.7% based upon extensive ground-truthing. Since similar digital and ASTER image information is available for Iran, an accurate landform map can now be produced for the whole country. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.
K A Hogan - One of the best experts on this subject based on the ideXlab platform.
-
late quaternary ice flow and sediment delivery through hinlopen trough northern svalbard margin submarine Landforms and depositional fan
Marine Geology, 2011Co-Authors: C L Batchelor, Julian A Dowdeswell, K A HoganAbstract:Abstract The morphology and distribution of submarine Landforms in Hinlopen Trough, Northern Svalbard margin, and the upper continental slope beyond, are investigated using swath-bathymetric data, together with side-scan sonar, acoustic profiler records and sediment cores. Sun-illuminated images reveal a number of landform assemblages on the sea floor of Hinlopen Trough and confirm that this depression was occupied by an ice stream during the Late Weichselian glaciation around 20 ka before present. The geomorphology of the inner-shelf is characterised by bedrock drumlins and ice-sculpted bedrock. There is a middle-shelf transition from a rock bed to an unconsolidated sedimentary bed that contains highly-attenuated drumlins and megaflutes formed within a dark grey, matrix-supported diamict, interpreted as subglacial till. Outer-shelf Landforms are mainly iceberg ploughmarks. The geomorphological imprint identified from Hinlopen Trough is similar to that of many former ice streams; the trough is dominated by elongate Landforms orientated parallel to the inferred flow direction and is lacking in transverse features indicative of inter-ice stream locations. A characteristic down-flow progression in landform elongation is also observed, suggesting an increase in ice velocity across the continental shelf. The lack of grounding-zone features imaged from swath-bathymetric data implies that deglaciation was probably rapid within the trough. A large depositional fan exists on the upper continental slope beyond the trough, characterised by debris flow deposits relating to the down-slope transport of glacigenic sediment. Order of magnitude calculations of the volume of glacigenic sediment on the continental slope indicate that the ice stream provided high rates of debris delivery of around 5–7.5 m/ka. This suggests that Hinlopen Trough ice stream represented a major route for the transfer of ice and debris to the Hinlopen Fan on the northern continental margin of Svalbard during the Late Weichselian glaciation.
-
submarine Landforms and ice sheet flow in the kvitoya trough northwestern barents sea
Quaternary Science Reviews, 2010Co-Authors: K A Hogan, Colm O Cofaigh, Julian A Dowdeswell, Jeffrey Evans, Riko Noormets, Martin JakobssonAbstract:High-resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in Kvitoya Trough, northwestern Barents Sea. A new swath-bathymetric dataset identifies three types of submarine landform in the study area (streamlined Landforms, meltwater channels and cavities, iceberg scours). Subglacially produced streamlined Landforms provide a record of ice flow through Kvitoya Trough during the last glaciation. Flow directions are inferred from the orientations of streamlined Landforms (drumlins, crag-and-tail features). Ice flowed northward for at least 135 km from an ice divide at the southern end of Kvitoya Trough. A large channel-cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice-sheet base. Modest landform elongation ratios and a lack of mega-scale glacial lineations suggest that, although ice in Kvitoya Trough was melting at the bed and flowed faster than the likely thin and cold-based ice on adjacent banks, a major ice stream probably did not occupy the trough. Retreat was relatively rapid after 14–13.5 14C kyr B.P. and probably progressed via ice sheet-bed decoupling in response to rising sea level. There is little evidence for still stands during ice retreat or of ice-proximal deglacial sediments. Relict iceberg scours in present-day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat.
Julian A Dowdeswell - One of the best experts on this subject based on the ideXlab platform.
-
Submarine Glacial Landforms
Submarine Geomorphology, 2017Co-Authors: Christine Batchelor, Julian A Dowdeswell, Dag OttesenAbstract:The development of a range of geophysical imaging techniques, including multi-beam swath bathymetry and shallow-acoustic profiling, has enabled the identification and interpretation of submarine glacial Landforms on and beneath the seafloor of formerly-glaciated continental margins. The analysis of these Landforms provides information about past ice-sheet dynamic behaviour and the mechanisms by which sediment is eroded, transported and deposited by ice sheets. Submarine glacial Landforms can be categorised into subglacial, ice-marginal and glacimarine features. The majority of subglacially produced Landforms, including mega-scale glacial lineations and drumlins, are elongate features that are orientated parallel to the direction of former ice flow. In contrast, ice-marginal Landforms, including moraines and grounding-zone wedges, are orientated transverse to the former ice-flow direction. Ice-marginal Landforms reveal the positions of still-stands or minor re-advances in the grounding-zone during general ice-sheet retreat. Glacimarine landform associations include ploughmarks that are formed by the grounding of iceberg keels on the seafloor, and smooth basin-fill sediments produced by suspension settling of material derived from meltwater plumes. The typical distribution of glacial Landforms on formerly glaciated continental margins is illustrated using the case study of the Norwegian continental shelf and slope. The locations of former fast-flowing ice streams are associated with deep cross-shelf troughs that contain elongate subglacial Landforms. Major glacial-sedimentary depocentres or trough-mouth fans are typically present on the continental slope beyond trough mouths. In contrast, relatively shallow inter-ice stream banks on the continental shelf are characterised by transverse moraine ridges and widespread iceberg ploughmarks.
-
late quaternary ice flow and sediment delivery through hinlopen trough northern svalbard margin submarine Landforms and depositional fan
Marine Geology, 2011Co-Authors: C L Batchelor, Julian A Dowdeswell, K A HoganAbstract:Abstract The morphology and distribution of submarine Landforms in Hinlopen Trough, Northern Svalbard margin, and the upper continental slope beyond, are investigated using swath-bathymetric data, together with side-scan sonar, acoustic profiler records and sediment cores. Sun-illuminated images reveal a number of landform assemblages on the sea floor of Hinlopen Trough and confirm that this depression was occupied by an ice stream during the Late Weichselian glaciation around 20 ka before present. The geomorphology of the inner-shelf is characterised by bedrock drumlins and ice-sculpted bedrock. There is a middle-shelf transition from a rock bed to an unconsolidated sedimentary bed that contains highly-attenuated drumlins and megaflutes formed within a dark grey, matrix-supported diamict, interpreted as subglacial till. Outer-shelf Landforms are mainly iceberg ploughmarks. The geomorphological imprint identified from Hinlopen Trough is similar to that of many former ice streams; the trough is dominated by elongate Landforms orientated parallel to the inferred flow direction and is lacking in transverse features indicative of inter-ice stream locations. A characteristic down-flow progression in landform elongation is also observed, suggesting an increase in ice velocity across the continental shelf. The lack of grounding-zone features imaged from swath-bathymetric data implies that deglaciation was probably rapid within the trough. A large depositional fan exists on the upper continental slope beyond the trough, characterised by debris flow deposits relating to the down-slope transport of glacigenic sediment. Order of magnitude calculations of the volume of glacigenic sediment on the continental slope indicate that the ice stream provided high rates of debris delivery of around 5–7.5 m/ka. This suggests that Hinlopen Trough ice stream represented a major route for the transfer of ice and debris to the Hinlopen Fan on the northern continental margin of Svalbard during the Late Weichselian glaciation.
-
submarine Landforms and ice sheet flow in the kvitoya trough northwestern barents sea
Quaternary Science Reviews, 2010Co-Authors: K A Hogan, Colm O Cofaigh, Julian A Dowdeswell, Jeffrey Evans, Riko Noormets, Martin JakobssonAbstract:High-resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in Kvitoya Trough, northwestern Barents Sea. A new swath-bathymetric dataset identifies three types of submarine landform in the study area (streamlined Landforms, meltwater channels and cavities, iceberg scours). Subglacially produced streamlined Landforms provide a record of ice flow through Kvitoya Trough during the last glaciation. Flow directions are inferred from the orientations of streamlined Landforms (drumlins, crag-and-tail features). Ice flowed northward for at least 135 km from an ice divide at the southern end of Kvitoya Trough. A large channel-cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice-sheet base. Modest landform elongation ratios and a lack of mega-scale glacial lineations suggest that, although ice in Kvitoya Trough was melting at the bed and flowed faster than the likely thin and cold-based ice on adjacent banks, a major ice stream probably did not occupy the trough. Retreat was relatively rapid after 14–13.5 14C kyr B.P. and probably progressed via ice sheet-bed decoupling in response to rising sea level. There is little evidence for still stands during ice retreat or of ice-proximal deglacial sediments. Relict iceberg scours in present-day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat.
-
geological constraints on antarctic palaeo ice stream retreat
Earth Surface Processes and Landforms, 2008Co-Authors: Colm O Cofaigh, Julian A Dowdeswell, Jeffrey Evans, Robert D LarterAbstract:Submarine Landforms preserved in bathymetric troughs on the Antarctic continental shelf show that the style of ice stream retreat across the shelf following the last glacial maximum varied between different troughs. Three styles of retreat are inferred from the geological evidence: rapid, episodic and slow. Rapid retreat by ice stream floatation and calving is recorded by the preservation of a landform assemblage of unmodified streamlined subglacial bedforms including mega-scale glacial lineations (MSGLs) that record streaming flow along these troughs. These elongate bedforms are not overprinted by recessional glacial Landforms formed transverse to ice flow such as moraines or grounding-zone wedges, and overlying deglacial sediments are thin. A second type of landform assemblage consists of MSGLs overprinted or interrupted by transverse grounding-zone wedges. This assemblage implies episodic retreat between successive grounding-zone positions. The third type of landform assemblage is that of numerous, closely spaced, recessional moraines and intermittent grounding-zone wedges that overlie and interrupt MSGLs. This assemblage records the slow retreat of grounded ice across the shelf. Variation in the style of ice stream retreat between the different bathymetric troughs indicates that Antarctic palaeo-ice-streams did not respond uniformly to external forcing at the end of the last glacial cycle. Rather, their diachronous retreat reflects the dominance of local controls in the form of bathymetry and drainage basin size. More broadly, these data show that retreat of marine-based ice sheets in areas of reverse bed slope is not necessarily catastrophic, and they provide important constraints for numerical models that attempt to predict the dynamics of large polar ice sheets. Copyright © 2008 John Wiley & Sons, Ltd.
Hossein Saadat - One of the best experts on this subject based on the ideXlab platform.
-
landform classification from a digital elevation model and satellite imagery
Geomorphology, 2008Co-Authors: Hossein Saadat, Robert Bonnell, F Sharifi, G R Mehuys, Mohammad Namdar, Sasan AleebrahimAbstract:The Iranian Soil and Water Research Institute has been involved in mapping the soils of Iran and classifying Landforms for the last 60 years. However, the accuracy of traditional landform maps is very low (about 55%). To date, aerial photographs and topographic maps have been used for landform classification studies. The principal objective of this research is to propose a quantitative approach for landform classification based on a 10-m resolution digital elevation model (DEM) and some use of an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image. In order to extract and identify the various Landforms, slope, elevation range, and stream network pattern were used as basic identifying parameters. These are extractable from a DEM. Further, ASTER images were required to identify the general outline shape of a landform type and the presence or absence of gravel. This study encompassed a relatively large watershed of 451 183 ha with a total elevation difference of 2445 m and a variety of Landforms from flat River Alluvial Plains to steep mountains. Classification accuracy ranged from 91.8 to 99.6% with an average of 96.7% based upon extensive ground-truthing. Since similar digital and ASTER image information is available for Iran, an accurate landform map can now be produced for the whole country. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.
