Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams

Conceptual ice stream land systems derived from geomorphological and sedimentological observations provide constraints on ice–meltwater–till–bedrock interactions on palaeo-ice stream beds. Within these land systems, the spatial distribution and formation processes of ribbed bedforms remain unclear. We explore the conditions under which these bedforms may develop and their spatial organization with (i) an experimental model that reproduces the dynamics of ice streams and subglacial land systems and (ii) an analysis of the distribution of ribbed bedforms on selected examples of palaeo-ice stream beds of the Laurentide Ice Sheet. We find that a specific kind of ribbed bedform can develop subglacially through soft-bed deformation, where the ice flow undergoes lateral or longitudinal velocity gradients and the ice–bed interface is unlubricated; oblique ribbed bedforms develop beneath lateral shear margins, whereas transverse ribbed bedforms develop below frontal lobes. We infer that (i) ribbed bedforms strike orthogonally to the compressing axis of the horizontal strain ellipse of the ice surface and (ii) their development reveals distinctive types of subglacial drainage patterns: linked cavities below lateral shear margins and efficient meltwater channels below frontal lobes. These ribbed bedforms may act as convenient geomorphic markers to reconstruct lateral and frontal margins, constrain ice flow dynamics, and infer meltwater drainage characteristics of palaeo-ice streams.

Ribbed bedforms, markers of palaeo-ice stream margins, basal meltwater drainage and ice flow dynamic

<p>Over the three last decades, great efforts have been undertaken by the glaciological community to characterize the behaviour of ice streams and better constrain the dynamics of ice sheets. Studies of modern ice stream beds reveal crucial information on ice-meltwater-till-bedrock interactions, but are restricted to punctual observations limiting the understanding of ice stream dynamics as a whole. Consequently, theoretical ice stream landsystems derived from geomorphological and sedimentological observations were developed to provide wider constraints on those interactions on palaeo-ice stream beds. Within these landsystems, the spatial distribution and formation processes of subglacial periodic bedforms transverse to the ice flow direction – ribbed bedforms – remain unclear. The purpose of this study is (i) to explore the conditions under which these ribbed bedforms develop and (ii) to constrain their spatial organisation along ice stream beds.  </p><p>We performed physical experiments with silicon putty (to simulate the ice), water (to simulate the meltwater) and sand (to simulate a soft sedimentary bed) to model the dynamics of ice streams and produce analog subglacial landsystems. We compare the results of these experiments with the distribution of ribbed bedforms on selected examples of palaeo-ice stream beds of the Laurentide Ice Sheet. Based on this comparison, we can draw several conclusions regarding the significance of ribbed bedforms in ice stream contexts:</p><ul><li>Ribbed bedforms tend to form where the ice flow undergoes high velocity gradients and the ice-bed interface is unlubricated. Where the ribs initiate, we hypothesize that high driving stresses generate high basal shear stresses, accommodated through bed deformation of the active uppermost part of the bed.</li> <li>Ribbed bedforms can develop subglacially from a flat sediment surface beneath shear margins (i.e., lateral ribbed bedforms) and stagnant lobes (i.e., submarginal ribbed bedforms) of ice streams, while they do not develop beneath surging lobes.</li> <li>The orientation of ribbed bedforms reflects the local stress state along the ice-bed interface, with transverse bedforms formed by compression beneath ice lobes and oblique bedforms formed by transgression below lateral shear margins.</li> <li>The development of ribbed bedforms where the ice-bed interface is unlubricated reveals distinctive types of discontinuous basal drainage systems below shear and lobe margins: linked-cavities and efficient meltwater channels respectively.</li> </ul><p>Ribbed bedforms could thus constitute convenient geomorphic markers for the reconstruction of palaeo-ice stream margins, palaeo-ice flow dynamics and palaeo-meltwater drainage characteristics.</p>

Ribbed bedforms in palaeo-ice streams reveal shear margin positions, lobe shutdown and the interaction of meltwater drainage and ice velocity patterns

Conceptual ice stream landsystems derived from geomorphological and sedimentological observations provide constraints on ice-meltwater-till-bedrock interactions on palaeo-ice stream beds. Within these landsystems, the spatial distribution and formation processes of ribbed bedforms remain unclear. We explore the conditions under which these bedforms develop and their spatial organisation with (i) an experimental model that reproduces the dynamics of ice streams and subglacial landsystems and (ii) an analysis of the distribution of ribbed bedforms on selected examples of paleo-ice stream beds of the Laurentide Ice Sheet. We find that a specific kind of ribbed bedforms can develop subglacially from a flat bed beneath shear margins (i.e., lateral ribbed bedforms) and lobes (i.e., submarginal ribbed bedforms) of ice streams. These bedforms initiate where the ice flow undergoes high velocity gradients and the ice-bed interface is unlubricated. We suggest that (i) their orientation reflects the local stress state along the ice-bed interface and (ii) their development reveals distinctive types of subglacial drainage patterns below these two kinds of margins: linked-cavities and efficient meltwater channels respectively. These ribbed bedforms are thus convenient geomorphic markers to reconstruct palaeo-ice stream margins and constrain palaeo-ice flow dynamics and palaeo-meltwater drainage characteristics.

Utilisation of E-Waste, Fly Ash in Manufacturing of Paver Blocks and Tiles

E-Waste that is increasing day by day turning into a major threat to public health and successively pollutes the setting. India ranks fifth in the world for e-waste generation; about a pair of million a lot of e-waste is generated associate rally and an unrevealed quantity of e-waste is foreign from alternative countries around the world. The aim of this project is to exchange cement with e-waste and fly ash in paver block, tiles and to chop back the worth of paver block and tiles compared thereto of convention concrete paver blocks and tiles. Use of concrete paver block and tiles square measure presently day after day turning into standard; they are used for paving of approaches, strategies and ton and collectively the pre-engineering building and pavements. Throughout this project, we've used e-waste in various proportions with quarry dirt and ash, coarse combination, compound, and metal-containing material and cement. This can be often one in every of the foremost effective ways that to avoid the buildup of e-waste which can be a non-degradable waste. This as an alternative saves the quanta of sand and clay that ought to be got eliminate from the dear stream beds. The e-waste getable in surplus quantity and thence the worth issue comes down. Collectively Coloring agents are added to the mixture to comprehend desired shades. Thence throughout this project, an endeavor is formed to review regarding the properties of the paver blocks and tiles that are ready-made pattern e-waste. The paver blocks and tiles were prepared and tested and so the results were mentioned.

Detection of toxic materials at Death Valley and Death Spring, a new ecosystem in Tashan District, Southern Iran

Death Valley and its stream form a unique landscape in the Tashan district of southern Iran. The water from the headstream of Death Spring to 100 meters downstream and the air around it are lethally dangerous and cause death. The color of the stream beds changes to five different colors. In this study, sampling of sediment and water took place in two seasons and at five stations. Historical information about the area was also collected and analyzed. The heavy metal concentrations in the water and sediment were high; in successive order from high to low, they were Fe > Al > Ag > Pb > Zn > Mn > As > Cu > Cr > Ni > Cd > Co > Sb. The toxic gas is H2S, and the treated concentration of this gas rises up to 410 ppm making the surrounding air toxic as well. The Gas emission has Geological origin. At the source of Death spring the Sulfur compounds in the water, soil, and sediment do not allow the growth of any macroscopic plants or animals. The current study aimed to identify the eco-touristic capacities and mortal danger in this valley, and to carry out environmental action plans, such as installing warning plates and notes to protect people and animals, so that all can benefit from the clean air and mineral water of 7 clean springs at the higher regions of Death Spring and enjoy the pleasant landscape of this area without being injured by the lethal gas of Death Valley. Other wonders of this area are also introduced.

Detection of toxic materials at Death Valley and Death Spring, a new ecosystem in Tashan District, Southern Iran

Death Valley and its stream form a unique landscape in the Tashan district of southern Iran. The water from the headstream of Death Spring to 100 meters downstream and the air around it are lethally dangerous and cause death. The color of the stream beds changes to five different colors. In this study, sampling of sediment and water took place in two seasons and at five stations. Historical information about the area was also collected and analyzed. The heavy metal concentrations in the water and sediment were high; in successive order from high to low, they were Fe > Al > Ag > Pb > Zn > Mn > As > Cu > Cr > Ni > Cd > Co > Sb. The toxic gas is H2S, and the treated concentration of this gas rises up to 410 ppm making the surrounding air toxic as well. The Gas emission has Geological origin. At the source of Death spring the Sulfur compounds in the water, soil, and sediment do not allow the growth of any macroscopic plants or animals. The current study aimed to identify the eco-touristic capacities and mortal danger in this valley, and to carry out environmental action plans, such as installing warning plates and notes to protect people and animals, so that all can benefit from the clean air and mineral water of 7 clean springs at the higher regions of Death Spring and enjoy the pleasant landscape of this area without being injured by the lethal gas of Death Valley. Other wonders of this area are also introduced.

Gravel and boulders mining from mountain stream beds

Mountain stream gravel is very often legally and illegally mined and gravel is removed from river beds sometimes on the very large scale which is disastrous for fluvial situation of rivers, for river ecology and river engineering works done for flood protection such as river revetments, bridges and all hydraulic structures. This situation makes a big problem for all river managers. Thus gravel mining of the mountain streams in the Polish Carpathians is the subject of many scientific studies when we observe river problems, but also it has a place in Slovakia. This paper deals with such problems additionally showing examples of such bad practices.

How dynamic are ice-stream beds?

Projections of sea-level rise contributions from West Antarctica's dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds, which may be important for subglacial traction, till continuity and landform development. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3–6 years apart, along a cumulative ∼ 60 km of profiles. Analysis of the correlation of bed picks between repeat surveys shows that 90 % of the bed displays no significant change despite the glacier increasing in speed by up to 40 % over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radar-sounded basal interface. Given the precision of our measurements, the upper limit of subglacial erosion observed here is 500 mm a−1, far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1.0 m a−1 previously reported from repeat geophysical surveys in West Antarctica.

Rare calciphilous diatoms from the genus Gomphonema (Bacillariophyta) in lotic waters of SE Poland

The aim of this work was to present a morphological description and ecological characteristics of a rare species from the Gomphonema genus, occurring in calcium-rich waters, along with its new occurrence sites. The research was carried out in flowing waters of mountain and sub-mountain streams and rivers in Poland: the Wołosaty, the Wisłoka, the San and their tributaries. The occurrence of many rare and new to Polish flora species from the genus Gomphonema was recorded: G. cuneolus E. Reichardt, G. drutelingense E. Reichardt, G. innocens E. Reichardt,G. lateripunctatum E. Reichardt & Lange-Bertalot, G. lippertii E. Reichardt & Lange-Bertalot and G. calcifugum Lange-Bertalot & E. Reichardt. These species occur mostly in alkaline or close-to-neutral waters with medium or low electrolytic conductivity (78–530 μS cm-1), low nutrient content and medium-to-high calcium ion content (12.4–76.4 mg l-1). Despite the rare occurrence in other parts of the world, the studied Gomphonema species has found favorable conditions in unpolluted and calcium-rich stream beds with flysch strata. The literature data define G. calcifugum as a non-calciphilous species, but this study shows that it can develop in a wide pH range and in calcium-rich waters.