Landform Assemblages Research Articles

Rapid geomorphological and sedimentological changes at a modern Alpine ice margin: lessons from the Gepatsch Glacier, Tirol, Austria

The Gepatsch Glacier in Tirol (Austria) is a rapidly retreating valley glacier whose host valley and forefield reveal subglacial, proglacial, and reworked sediment–landform assemblages. Structures include roches moutonées develop on gneiss, compound bedrock-sediment bedforms (crag and tail structures), flutes, and small diamicton ridges. The glacial sediments and landforms are undergoing incision and terrace development by meltwater streams. Glacial geomorphological and surface geological maps, in concert with elevation models of difference between July 2019 and July 2020 highlight considerable changes to the forefield over a 12-month time period. Till exposed within the last 20 years has undergone substantial mass wasting and re-deposition as subaerial mass flows, or reworked into stream deposits. The lee sides of many roches moutonées completely lack subglacial sediment, and instead contain a sand and gravel deposit interpreted to result from glaciofluvial deposition. Thus, insights into the rates of erosion and deposition in a complex, proglacial setting, allow some of these processes to be quantified for the first time. Repeated monitoring of glacier forefields is expected to yield a better understanding of the preservation potential of proglacial sedimentary facies, and hence their preservation potential in Earth's sedimentary record. Supplementary material: A comparison of 3D model parameters for 2019 and 2020 data is available at https://doi.org/10.6084/m9.figshare.c.5664299

The morphology of altiplanation in interior Alaska

ABSTRACT Altiplanation (cryoplanation) terraces are conspicuous and widespread elements of upland landscapes in Alaska’s interior. They occur in staircase-like series, primarily along divides in ridge-crest positions, and as summit platforms. Flanks (side slopes) consist of a steep upper section composed of coarse clastic debris and amorphous solifluction forms, grading through a break in slope (the ‘solischrund’) to a gentler lower section (cryopediment) dominated by well-defined solifluction lobes and low-order hillslope hydrological networks. An individual terrace unit consists of a steep scarp (riser) and a subjacent gently inclined tread (platform). A sequential group or series of adjacent terrace units, descending from a summit platform along ridge crests, are referred to collectively as an altiplanorium. Altiplanation terraces are a prominent feature of the altitudinal zonal arrangement of landscape phenomena in interior Alaska, and are confined to the upland periglacial zone between 915 and 1675 m.a.s.l. They are positioned below the contemporary snowline. Three study areas are given detailed verbal, cartographic, and photographic description. These areas (Mount Fairplay, High Valley/Denali Mountain, and Goodpaster Uplands) could serve as type localities for altiplanation landform assemblages. An appendix identifies the locations of many other areas in the Alaskan interior containing well-developed altiplanation landforms, and demonstrates the widespread geographic distribution of these landforms.

Proglacial landform assemblage in a rapidly retreating cirque glacier due to temperature increase since 1970, Fuegian Andes, Argentina

The general trend of glacial retreat since the Little Ice Age has shown an acceleration during the last decades in Southern Argentine and Chilean Patagonia. The Fuegian Andes climatic records report an irregular mean annual temperature increase since 1970, with acceleration from 2015, and the Chato Glacier, as other regional cirque glaciers, has undergone a rapid ice front retreat. A detailed mapping of the proglacial area of the Chato Glacier allowed the identification of a landform assemblage related to the glacier retreat during the last decades. In this paper morphological and sedimentological features of this peculiar landform assemblage, generated in an intense glacial ablation environment, are described and the causes of their origin are discussed. Among the most remarkable landforms annual moraines, hummocky moraines, esker-like landforms, flutes, kettle ponds, dirt cones, glacifluvial deposits, pronival ramparts and collapsed moraines are found. The multitemporal analysis of the Chato Glacier retreat allowed us to interpret that most of these landforms were generated when the landscape became ice-free after 2005. The Chato Glacier cirque floor gentle slope, the thin-ice thickness and the occurrence of a rocky threshold near the glacier front would have promoted the rapid glacier thinning and the disconnection of dead ice. This context, together with the sediments and meltwater availability, would have favored the development of this landform assemblage which is ephemeral due to its high susceptibility to erosion.

The role of glacial dynamics in the development of ice divides and the Horseshoe Intersection Zone of the northeastern Labrador Sector of the Laurentide Ice Sheet

The Labrador Sector of the Laurentide Ice Sheet is characterized by a complex network of ice divides and an extensive landform record outlining two broad and opposing ice flows that are separated by a narrow Horseshoe Intersection Zone (HIZ). This geomorphic system gave rise to contrasting reconstructions, which reflect uncertainties on the temporal evolution of ice divides, the nature and age of the main landform systems and the overall pattern of ice retreat during the last deglaciation. Here, we address these issues through systematic mapping of glacial landforms and ice-flow indicators in a large area of northeastern Quebec and Labrador. The application of cosmogenic (10Be and 26Al) dating to esker-fed glaciomarine deltas and different rock surfaces brings new constraints on the chronological framework and insights on the subglacial thermal regime. Our results outline four main landform assemblages, two of which relating to a major system of opposite ice flows that delineate the position of the eastern Ancestral Labrador ice divide. Our reconstruction shows that the HIZ occurs several tens of km to the west of this divide and that these two features are genetically distinct. The HIZ relates to the late-glacial development of ice streams showing a massive convergent ice flow into Ungava Bay. The upstream extent of this ice flow system shows a strong coupling with the outline of Ungava Bay drainage divide, suggesting that the configuration of the HIZ could be the expression of a topographic control on the late-glacial ice sheet dynamics. Landforms also indicate a significant shift in the deglaciation mode, which evolved from an overall warm-based to an areally-confined cold-based ice retreat near the center of the former ice mass – a change in dynamics that also played a role in the configuration of the HIZ. Overall, areas indicative of cold-based ice conditions are limited to highly elevated terrains, thus ruling out models arguing for an extensive cold-based ice cover over Ungava Bay throughout the last deglaciation.

Glacial geomorphology of the Ahuriri River valley, central Southern Alps, New Zealand

ABSTRACT Detailed geomorphological mapping of ice-related and post-glacial landforms is widely used to explain past glacial fluctuations and dynamics. Here we present the first detailed glacial geomorphological description of the landform assemblages produced by the former Ahuriri Glacier, Southern Alps, New Zealand (44° 15′ S, 169° 36′ E). The Southern Alps of New Zealand experienced multiple episodes of glaciation during the Late Quaternary with large mountain glaciers in many valleys, but very little is known about the Ahuriri River valley, one of the main tributaries of the Waitaki River. We selected a region extending approximately 45 km downstream from the headwaters of the Ahuriri River covering an area of about 532 km2. Our goal was to create a detailed 1:38,000 scale glacial geomorphological map of this area and provide a geomorphological context to support future geochronological work. Glacial geomorphological mapping was performed by combining several field investigations and remote sensing surveys. We provided high-resolution spatial information for all the glacial-related landforms shown on the map (see main Map). The distribution of post-glacial landforms in the middle and lower section of the main valley outline at least three advances or stillstand phases of past glaciers and suggesting the maximum length (∼41 km) of the former glacier during the Last Glacial Maximum. Most of the tributary valleys were also probably covered by ice at this time. Other prominent but smaller size moraine landforms, mostly in the tributary river valleys, also suggest relatively small, post-glacial advance phases of former glaciers.

Landform evolution of Oudemans crater and its bounding plateau plains on Mars: Geomorphological constraints on the Tharsis ice-cap hypothesis

In this study we address the question of whether the Tharsis rise that occupies ~25 % of the surface area of Mars was once covered by an ice cap, and the sudden ice-cap melting was responsible for the catastrophic development of the Late Hesperian (3.5-3.6 Ga) circum-Tharsis giant (>1000s km in length) outflow channels. To achieve this goal, we conducted geomorphologic mapping across the Oudemans crater basin (~125 km in diameter) at elevations of ~2.7 km to ~5.0 km and its bounding plateau plains at elevations of ~5.3 km to ~6.7 km in the central Tharsis rise. Our work shows that the Oudemans-impact-induced landforms were superposed by a suite of younger landform assemblages, which consist of horn-like peaks, arête-like ridges, cirque-like depressions, hanging-valley-like features, trim-line-like escarpments, lobate ridges, striated, pitted and hummocky terrains, and features resembling drumlins, crag-and-tails and roches moutonnées. A plateau-plain striated terrain on a hummocky surface exhibits streamlined linear ridges that are 400-2000 m wide and up to ~17 km long. The average length-width ratio (~9), shape, surface texture, and associated washboard landform pattern of the linear morphological features in the striated terrain on Mars are comparable to mega-scale glacial lineations (MSGLs) on Earth. Using well-understood Earth analogues as a guide, we interpret the post-Oudemans-impact landform assemblages to have formed during regional ice-sheet-style glaciation. We further suggest the striated terrain on the plateau plains to have been generated by a fast-moving ice stream in a regional ice sheet that filled 4-km deep Oudemans crater and covered the crater-bounding plateau plains in the central Tharsis rise. The volume of the glacier ice stored in the Oudemans crater basin alone is estimated on the order of ~200,000 km3. The shape of the inferred glacier-induced landforms and their cross-cutting relationships require early northward-flowing northward-advancing glaciation, followed by southward-flowing northward-retreating glaciation. The size-frequency distribution of the craters superposed on top of the interpreted glaciated landforms in the mapped area yields a glaciation age of ca. 3.5 Ga, coeval with the estimated age of the interpreted glacial landforms along the 2000-km long Valles Marineris trough zone east of the study area. The inferred glaciation age is also coeval with the development of the circum-Tharsis outflow channels. Although our work supports the Tharsis ice-cap hypothesis, the full extent of the ice cap within and possibly beyond the Tharsis rise remains unconstrained.

Interaction of multiple ice streams on the Malin Shelf during deglaciation of the last British–Irish Ice Sheet

ABSTRACTThe Malin Shelf, off north‐west Ireland, was an important zone of confluence for marine‐based ice streams of the former British–Irish Ice Sheet (BIIS). Legacy geophysical datasets are used to construct models of the seismic character, relative age and distribution of shelf sediments and landforms. Buried and surface landform assemblages provide evidence that during deglaciation of the Late Devensian BIIS, the region was occupied not by a single Hebrides Ice Stream as previously proposed, but by four discrete ice streams, here referred to as the Sea of the Hebrides (SHIS), Inner Hebrides, North Channel and Tory Island ice streams. Our observations of stratigraphic relationships between the deposits of these ice streams indicate physical interactions between them during shelf deglaciation. We interpret an initial dominant cross‐shelf flow along the SHIS impeding cross‐shelf ice flow from other ice sheet sectors. Following withdrawal of the SHIS grounding line from the shelf edge to mid‐shelf bathymetric highs during deglaciation, a reconfiguration of ice sheet flow paths allowed the expansion of smaller cross‐shelf ice streams draining central Scotland and north‐western Ireland. This internal dynamic behaviour provides a possible physical analogue for time‐transgressive flow patterns reported for outlets draining the West Antarctic Ice Sheet.

Evidence of ice streaming and ice tongue shutdown in western Latvia: revealed from the mapping of crevasse-squeeze ridges

Glacial geomorphological mapping of western Latvia using a 1-m-resolution digital elevation model generated from airborne LiDAR data has revealed two sets of mega-scale glacial lineations (MSGLs), one of which is superimposed by crevasse-squeeze ridges (CSRs). CSRs occur as a dense ridge network with a dominant orientation of ridges perpendicular to the ice flow direction. The landform assemblage is interpreted as evidence for two separate phases of fast ice flow with different ice flow directions during the overall deglaciation of the Fennoscandian Ice Sheet (FIS). The first fast ice flow phase occurred from the northwest by the Usma Ice Lobe that extended in the Eastern Kursa Upland. The second fast ice flow occurred from the north by the Venta Ice Tongue in a narrow flow corridor limited mainly to the Kursa Lowland. Active ice streaming caused ice crevassing perpendicular to the ice flow direction and formation of CSRs by squeezing of subglacial till into basal crevasses. A good preservation of the CSRs and general lack of recessional moraines suggest widespread stagnation and ice mass melting after the shutdown of the Venta Ice Tongue followed by the formation of the Venta-Usma ice-dammed lake and glaciolacustrine deposition in the lowest areas of lowland. Our data provide the first evidence of CSRs in the south-eastern terrestrial sector of the FIS suggesting the dynamic ice streaming or surging behaviour of the ice lobes and tongues in this region during deglaciation.

Surface velocity fields of active rock glaciers and ice‐debris complexes in the Central Andes of Argentina

AbstractRock glaciers and transitional ice‐debris complexes predominate the Central Andean landform assemblage, yet regional studies on their state of activity and their kinematics remain sparse. Here we utilize the national glacier inventory of Argentina to quantify surface velocity fields of 244 rock glaciers and 51 ice‐debris complexes, located in the Cordón del Plata range, Argentina. Applying a feature‐tracking approach to repeated RapidEye satellite imagery acquired between 2010 and 2017/18, we find mean displacement rates between 0.37 and 2.61 m year−1 for 149 landforms, while for the remaining 146 features, surface movement remains below our level of detection. We compare our satellite‐derived velocity fields with ground‐truth data from two local field sites and find closely matching results in magnitude and spatial distribution. With average displacement of one‐third of the active rock glaciers and ice‐debris complexes exceeding 1 m year−1, the region hosts an exceptional number of fast‐flowing periglacial landforms, compared to other mountain belts. Using a random forest model, we test the predictive power of 25 morphometric and topoclimatic candidate predictors for modelling the state of activity of rock glaciers and ice‐debris complexes on two different scales. For entire landforms and individual landform segments, constructed along displacement centrelines, we can predict the state of activity with overall accuracies of 70.08% (mean AUROC = 0.785) and 74.86% (mean AUROC = 0.753), respectively. While topoclimatic parameters such as solar radiation and elevation are most important for entire landforms, geometric parameters become more important at the scale of landform segments. Despite tentative correlations between local slope and surface kinematics, our results point to factors integrating slope and distance to the source to govern local deformation. We conclude that feature tracking in optical imagery is feasible for regional studies in remote regions and provides valuable insight into the current state of the Andean cryosphere. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Glacial dynamics and deglaciation history of Hambergbukta reconstructed from submarine landforms and sediment cores, SE Spitsbergen, Svalbard

The submarine landforms and shallow sediment record are presented from Hambergbukta, southeastern Spitsbergen using swath‐bathymetric, subbottom acoustic, and sediment core data. The mapped landforms include large terminal and end‐moraines with associated debrisflow aprons on their distal flanks, drumlinized till surface, glacial lineations, medial and retreat moraines, crevasse squeeze ridge networks, eskers, as well as iceberg‐produced terraces and plough‐marks. Analysis of the landforms and landform assemblages in combination with the sediment core data and aerial imagery studies reveal a complex and dynamic glacial history of Hambergbukta. We present a detailed history of Hambergbreen glacier indicating two previously unknown surges as well as new details on the nature of the subsequent ice‐margin retreat. The results from two gravity cores combined with the shallow acoustic stratigraphy and high‐resolution bathymetry suggest that the c. AD 1900 surge was less extensive than previously thought and the retreat was most likely rapid after the c. AD 1900 and 1957 surges of the Hambergbreen. Mixed benthic foraminifera collected from the outer fjord basin date to 2456 cal. a BP, suggesting older sediments were re‐worked by the c. AD 1900 surge. This highlights the importance of exercising caution when using foraminifers for dating surge events in fjord basins enclosed by prominent end‐moraines.

Glacial geomorphology of the High Gredos Massif: Gredos and Pinar valleys (Iberian Central System, Spain)

ABSTRACT We present a detailed geomorphological map of the landform assemblages originated by the two major paleoglaciers of the Sierra de Gredos mountain range in the Spanish Iberian Central System. Based on previous works, our map focused on the features formed by Gredos and Pinar paleoglaciers during the last glaciation and subsequent glacial events. Based on a remote sensing analysis and exhaustive field surveys, we identified with great accuracy the local distribution of glacial, periglacial, mass movement, structural, fluvial, and lacustrine features. We recognized three main glacial geomorphological formations representing: (i) the maximum glacial extension reached (peripheral deposits); (ii) the culmination of glacial conditions (principal moraines) and (iii) the local glacial withdrawal (internal deposits). Our map offers a renewed spatial framework on which to conduct higher-resolution glacial chronologies, especially of Late Glacial and Holocene glacial activity, providing key information for performing future paleoclimatic reconstructions of the northern hemisphere mid-latitudes.

Sinuous ridges in Chukhung crater, Tempe Terra, Mars: Implications for fluvial, glacial, and glaciofluvial activity

We present a geomorphic map of Chukhung crater (38.47°N, 72.42°W) in central Tempe Terra, Mars. Chukhung crater formed ~3.6–2.1 Ga, between the early Hesperian and early Amazonian periods of Mars' geologic history. It hosts dendritic networks of crater wall valleys, broad crater floor valleys, mid- to late-Amazonian-aged debris-covered glaciers, moraine-like deposits, and a radial assemblage of sinuous ridge landforms. We explore the origins of landforms in Chukhung crater, focusing in particular upon the sinuous ridges. In northern Chukhung crater, sinuous ridges extend downslope from fluvial valley systems on the northern crater wall. We interpret the northern sinuous ridges as inverted paleochannels: ridges formed by exhumation of resistant and/or indurated fluvial channel fill deposits. The origins of sinuous ridges on the southern floor of Chukhung crater are more ambiguous. They emerge from beneath moraine-like ridges which bound extant debris-covered glaciers extending from the southern wall of the crater. The southern sinuous ridges have numerous morphological and contextual similarities to eskers: ridges of glaciofluvial sediment deposited in meltwater conduits within or beneath wet-based glaciers. The close proximity of the northern and southern sinuous ridges, however, calls into question an interpretation which ascribes a different origin to each set. The similarity in the overarching process between esker and inverted channel formation (i.e., exposure by the removal of a bounding medium, be that ice or sediments/rock) results in convergence of form between eskers and inverted paleochannels. We discuss the esker-like characteristics of the southern sinuous ridges in detail, and argue that one of two ridge populations in southern Chukhung crater is best explained by the esker hypothesis while the other could be explained under either the esker or the inverted paleochannel hypothesis. Regardless of the specific formation mechanism for the southern sinuous ridges, we find that Chukhung crater has undergone significant modification by liquid water since its formation. The northern sinuous ridges and associated crater-wall valleys provide evidence for subaerial drainage of precipitation and/or snowmelt. This suggests that Chukhung crater, and possibly the surrounding region, experienced unusually warm and wet episodes between the early Hesperian and mid Amazonian. If some or all of the southern sinuous ridges are eskers, they could provide evidence for an additional influence of glacial meltwater in Chukhung crater during the mid-to-late Amazonian. If wet-based glaciation did occur in Chukhung crater, the location of the crater between major branches of the Tempe Fossae tectonic rift system would add to the growing body of evidence that elevated geothermal heat flux was an important driver of localized occurrences of recent wet-based glaciation on Mars.

Early paleozoic tropical paleokarst geomorphology predating terrestrial plant growth in the tahe oilfield, Northwest China

A deeply buried tropical paleokarst landscape that predates terrestrial plant growth was discovered in West District 10 of the Tahe Oilfield, located on the northern margin of the Tarim Basin in the Xinjiang Uygur Autonomous Region of northwestern China. The paleokarst unconformity surface at depths deeper than ~6000 m had been subjected to subaerial karstification under humid tropical climatic conditions during the first hiatus period in the Early Paleozoic. A high-quality, full-azimuthal 3D seismic survey was conducted in this study area (area of 10 × 10 km2) in order to visualize the buried paleokarst landscape with high-resolution seismic data. With this data and previous geological, geochemical, and paleomagnetic data, we reconstructed the large-scale paleokarst landform assemblage, compared it to a modern humid tropical/subtropical karst, and investigated the different controlling factors for the formation of the paleokarst and the modern karst. Results show that (1) the original landform assemblages of the tropical paleokarst landscape are distinct from those of the modern humid tropical/subtropical karst geomorphology; (2) the paleokarst denudation surface that formed in the Early Paleozoic was relatively smooth with shallow depressions, and the relative relief was less than that of the modern tropical/subtropical cockpit karst area; (3) during the time of epigenetic paleo-karstification, lithological, hydrogeological, and climate conditions were optimal for the formation of cockpit karst. The tropical paleokarst landscape demonstrates that extensive terrestrial plant growth plays an important role in creating large-scale karst landform assemblages of peak clusters and depressions (cockpit karst).

Interpretation, age and significance of a relict paraglacial and periglacial boulder-dominated landform assemblage in Alnesdalen, Romsdalsalpane, southern Norway

A boulder-dominated landform assemblage in an alpine setting in Norway is described, interpreted and dated using a combination of Schmidt-hammer exposure-age dating (SHD) and cosmogenic 10Be surface-exposure dating. The origin and formation of these features is determined from their morphology, topographic setting and age. Three main components of the assemblage are recognized. First a ~300 m long and ~160 m wide, tongue-shaped rock-slope failure with a SHD age of 11.49 ± 0.82–12.96 ± 0.86 ka is identified on the basis of its planform, thickness, ‘runout distance’ and association with a fractured backing scarp. This is interpreted as a relict paraglacial landform triggered by deglaciation. Second, a 400-m long unequivocal pronival (protalus) rampart with an SHD age of 6.95 ± 0.97–8.35 ± 1.21 ka is identified on the basis of its narrow ridge form aligned close to the foot of an extensive talus slope. Although formation of the rampart probably commenced with deglaciation, the younger SHD ages indicate formation at a diminishing rate through the Holocene. Third, a ~550 m by ~150 m lobate component with transverse ridges, longitudinal and transverse depressions and enclosed pits, previously identified as a rock glacier, is dated to 11.33 ± 0.83–13.33 ± 0.90 ka with the Schmidt hammer and between 13.3 ± 2.0–14.7 ± 2.0 ka with 10Be. This third component may also be a product of rock-slope failure but attribution to rock-glacier creep associated with either interstitial ice (permafrost) or buried glacier ice during the Allerød Interstadial – Younger Dryas Stadial, and to which one or more rock-slope failures contributed debris, cannot be rejected. The advantages and limitations of compiling such evidence for identifying, differentiating and classifying apparently similar boulder-dominated colluvial landforms are exemplified.

An index to assess the extent and success of river and floodplain restoration: Recognising dynamic response trajectories and applying a process‐based approach to managing river recovery

AbstractHow should the success of river and floodplain restoration be assessed? What should we be restoring? We contend that the benchmark for restoration should be the river in its “natural,” that is, quasi‐equilibrium condition prior to deliberate modification. The pre‐modification condition of the river represents a quasi‐equilibrium state in which the river accommodates and adjusts to catchment water and sediment fluxes, whether in a pristine or modified catchment. The resulting assemblage of river landforms (e.g., bars, channels, backwaters) is in balance with the prevailing flood and sediment regime. Furthermore, equilibrium channel forms can adjust to changes in, for example, flood magnitude and frequency via for example, channel expansion or contraction. A restored river system is one that once was anthropogenically restricted, but now has regained capacity to adjust its form. River restoration needs understanding of the history and trajectory of pre‐modification channels, so that the “right” river type can be restored. To assess the scope and success of restoration, we propose using a natural character index (NCI). The NCI is the ratio between a parameter which describes the form and function of a river now (observed) and the same parameter measured at a point or points in time past (expected). Exemplar parameters include sinuosity, floodplain width, active channel width, bar area (at a given flow) and riparian vegetation. Measurement of these parameters utilizes a combination of aerial photos, archive maps and LiDAR‐derived terrain models, the availability of which necessarily limits and determines what parameters can be used in NCI assessment. LiDAR is a useful tool providing an opportunity to comprehend pre‐modification river and floodplain character. We illustrate the NCI concept and its potential for use in assessing restoration effects using examples from New Zealand, Spain and Croatia. The result is an index of use as a “first cut” preliminary assessment for river practitioners.

Holocene evolution and Anthropocene destruction of the Krishna Delta on the east coast of India: Delta lobe shifts, human impacts, and sea-level history

The Holocene evolution of the Krishna Delta was inferred using landform characteristics and 11 sediment cores with 59 Accelerator Mass Spectrometry 14C dates. The landform assemblages in a 5880 km2 area of the Krishna Delta indicate an upper (landward) river-built fluvial plain and a lower (seaward) marine-built beach-ridge plain. Holocene sediment unconformably overlying a Pleistocene basement consists of 11 sedimentary facies, mainly shallowing-upward and deltaic succession. Sea level indicators such as the basal mangrove peat layers above the Pleistocene basement and the foreshore sediments indicate that the sea level rose from −9 m to −3 m during 8.3–6.3 cal ky BP, and stabilised at the present level around 5 cal ky BP. The 3539 km2 area of the Krishna Delta beach-ridge plain developed in five major stages during the last 6 cal ky, with distinct lateral and seaward migration of delta lobes (depocentre shifts). Delta progradation accelerated in the last 500 years, forming an out-building lobate delta. However, predominant erosion along the sediment-starved coast during the past five decades, due to impoundment of riverine inputs at the burgeoning upstream dams, has pushed the Krishna Delta into a persistent destruction phase.

Mapping Glacier Forelands Based on UAV BVLOS Operation in Antarctica

The aim of this article is to show geomorphological mapping of remote Antarctic locations using images taken by a fixed-wing unmanned aerial vehicle (UAV) during the Beyond Visual Line of Sight (BVLOS) operations. We mapped landform assemblages developed in forelands of Ecology Glacier (EGF), Sphinx Glacier (SGF) and Baranowski Glacier (BGF) in Antarctic Specially Protected Area No. 128 (ASPA 128) on King George Island (South Shetland Islands) and inferred about glacial dynamics. The orthophoto and digital elevation model allowed for geomorphological mapping of glacial forelands, including (i) glacial depositional landforms, (ii) fluvial and fluvioglacial landforms, (iii) littoral and lacustrine landforms, (iv) bodies of water, and (v) other. The largest area is occupied by ground moraine and glacial lagoons on EGF and BGF. The most profound features of EGF are the large latero-frontal moraine ridges from Little Ice Age and the first half of the 20th century. Large areas of ground moraine, frequently fluted and marked with large recessional moraine ridges, dominate on SGF. A significant percentage of bedrock outcrops and end moraine complexes characterize BGF. The landform assemblages are typical for discontinuous fast ice flow of tidewater glaciers over a deformable bed. It is inferred that ice flow velocity decreased as a result of recession from the sea coast, resulting in a significant decrease in the length of ice cliffs and decrease in calving rate. Image acquisition during the fixed-wing UAV BVLOS operation proved to be a very robust technique in harsh polar conditions of King George Island.

The Geomorphosite Potential of the Badlands Around Küpyar, Manisa, Turkey

The formation of rills and gullies represents an important indicator of land degradation and generates some of the highest erosion rates in the world. Nonetheless, in certain places, badland sites characterized by intense rill and gully erosion have become important natural tourist attractions. Many parts of Turkey are subjected to these types of erosion, but the possibility of using badlands as geomorphosites for tourism and education has yet to be explored. The area around Kupyar Hill, Manisa Province, hosts an interesting assemblage of landforms that have developed as a result of intensive rilling and gullying. These features have attracted the attention of local mountaineering and nature sports clubs, and this has helped to enable the area to become a tourist destination. The main objective of this study was to evaluate whether the landform assemblage hereabouts has the potential to be designated as a geomorphosite for tourism and education. Initially, it was necessary to identify all the clubs that include this region in their activity programs. Thereafter, it was possible to conduct face-to-face interviews with club managers, to obtain information about their routes, and to analyze photographs on the basis of pictorial semiotics. A questionnaire was completed by 108 individuals who visited Kupyar. The results suggest that visitors are not well informed about the processes that have led to formation of the rills and gullies, but there is a clear interest in these features and their development. The esthetic, economic, educational, scientific, and touristic value of the region was analyzed within the framework of different geomorphosite assessment methods. Those areas characterized by rilling and gullying were delimitated during detailed field research, and a geomorphosite map was produced with two routes that can be used for geotourism and geoeducation. Protecting this area as a geomorphosite appears to represent the most progressive decision that could be taken in terms of land use planning. Moreover, it could help to generate new sources of income for the local people and stem emigration from rural settlements to neighboring towns and cities.

The changing extent of marine-terminating glaciers and ice caps in northeastern Svalbard since the ‘Little Ice Age’ from marine-geophysical records

Climate warming in Svalbard since the end of the ‘Little Ice Age’ early in the 20th century has reduced glacier extent in the archipelago. Previous attempts to reconstruct ‘Little Ice Age’ glacier limits have encountered problems in specifying the area of tidewater glacier advances because it is difficult to estimate the past positions of their marine termini. Multibeam echo-sounding data are needed to map past glacier extent offshore, especially in open-marine settings where subaerial lateral moraines cannot be used due to the absence of fjord walls. We use the submarine glacial landform record to measure the recent limits of advance of over 30 marine-terminating northeastern Svalbard glaciers and ice caps. Our results demonstrate that previous work has underestimated the ice-covered area relative to today by about 40% for northeastern Svalbard (excluding southeast Austfonna) because marine-geophysical evidence in the form of submarine terminal moraines was not included. We show that the recent ice extent was 1753 km2larger than today over our full area of multibeam data coverage; about 5% of the total modern ice cover of Svalbard. It has often been assumed that moraine ridges located within a few kilometres of modern ice fronts in Svalbard represent either a ‘Little Ice Age’ maximum or relate to surge activity over the past century or so. In the marine environment of northeastern Svalbard, this timing can often be confirmed by reference to early historical maps and aerial photographs. Assemblages of submarine glacial landforms inshore of recently deposited terminal moraines suggest whether a recent advance may be a result of surging or ‘Little Ice Age’ climatic cooling relative to today. However, older terminal moraines do exist in the archipelago, as shown by radiocarbon and10Be dating of Holocene moraine ridges.

Late Quaternary paleoseismicity of the Xiadian fault in the North China Plain with implications for earthquake potential

The Xiadian fault is a crucial seismogenic structure in the North China Plain because of the 1679 A.D. Sanhe–Pinggu M8 earthquake. However, ~12 km of the coseismic surface rupture does not match the worldwide statistical relationship between magnitudes and rupture lengths. Paleoseismicity research can assist in resolving this debate. In this study, the synthesized data from geologic investigations, satellite image interpretations, geomorphic mapping, trench logging and sample dating show that the Xiadian fault undergone strong deformation in the Late Quaternary with a characteristic assemblage of landforms, including linear scarps, troughs, sag ponds, small horsts and grabens, and at least eight paleo-earthquake events can be observed. The coseismic displacements are not exactly the same but instead show a range of variation from ~1.4 ± 0.1 m to ~0.9 ± 0.1 m on average, and the median interval between the strong earthquakes was estimated at ~2820 ± 561 years, with an uncertainty value of 0.199. The quasi-periodicity behavior of the Xiadian fault is not as obvious as that of structures in the plate boundary. The surface rupture traces of the M8 earthquake, which is composed of 6 segments in an echelon pattern with a single length, vary from ~1 km to ~5 km. The asymmetric bell-shaped displacement distribution tends to approach a maximum in the central part in Pangezhuang village while gradually decreasing toward the tips in East Liuhetun and Dongxing villages; this suggests that the surface rupture of this event is may be only ~12 km long, although underlying causes require further study.