Terrace Surfaces Research Articles

Effects of surface vacancy-adatom pair formation on PFC tungsten surface morphological response

We report a simulation study of the effect of He-irradiation-induced surface vacancy-adatom pair formation on the surface morphological evolution of plasma-facing component (PFC) tungsten and examine a number of factors that impact such evolution. Our analysis is based on self-consistent dynamical simulations according to an atomistically-informed, continuum-scale surface evolution model that has been developed following a hierarchical multiscale modeling strategy and can access the spatiotemporal scales of relevance to fuzz formation. The model accounts for the flux of surface adatoms generated as a result of the surface vacancy-adatom pair formation effect upon He implantation, which contributes to the anisotropic growth of surface nanostructural features due to the different rates of adatom diffusion along and across step edges of islands on the tungsten surface. We have carried out atomic-scale computations of optimal diffusion pathways along and across island step edges on the W(110) surface and calculated Ehrlich–Schwoebel (ES) barriers in adatom diffusion along and across such step edges. This aspect of surface adatom diffusion contributes to anisotropic surface atomic fluxes, terrace and step diffusive currents, and has been incorporated into our PFC surface evolution model, which predicts the formation of preferentially aligned nanoridge stripe patterns on the PFC surface. We establish that these anisotropic diffusive currents accelerate nanotendril growth on the PFC surface and the onset of surface nanostructure pattern formation. We also explore systematically the dependence of the PFC surface morphological response on the surface temperature and He ion incident flux, characterize in detail the resulting surface topographies and growth kinetics, and compare the predicted surface morphologies with experimental observations. Our simulation predictions for the emerging surface nanostructure patterns under certain plasma exposure conditions are consistent with experimental findings in the literature.

Some geomorphological implications of recent archaeological investigations on river terraces of the River Dee, Aberdeenshire

Excavation and survey of archaeological sites have in recent years generated new data on the chronology of river terraces on the River Dee between Banchory and Peterculter in Aberdeenshire. Terrace fragments have been mapped and correlated on altitudinal grounds, for the first time. Five terrace surfaces are identified and named, refining the terminology of the British Geological Survey. Three are distinct surfaces within the Lochton Sand and Gravel Formation. The relation between them, regional deglaciation and the formation of the Late Devensian Loch of Park, north of Crathes, suggests some time separated their development. Below these, a fourth terrace, the Camphill Terrace, is dated to before the Windermere Interstadial by finds of Late Upper Palaeolithic flints. The Camphill Terrace is argued to have been the active valley floor within the Younger Dryas also. Timing of incision from the Camphill Terrace is not understood: interpretations are different at three archaeological sites. The youngest terrace fill and surface, the Maryculter Terrace, began to form c . 5000 years ago.

EFEITO DOS DEFEITOS DE SUPERFÍCIE E DO pH NA ADSORÇÃO E NA CATÁLISE DA ELETRO-OXIDAÇÃO DE CO EM SUPERFÍCIES MODELOS DE PLATINA

SURFACE DEFECTS AND pH EFFECTS ON ADSORPTION AND CATALYSIS OF CO ELECTRO-OXIDATION ON MODEL PLATINUM SURFACES. Platinum is one of the well-known catalytic materials for which the electro-oxidation of carbon monoxide better behaves as a sensitive reaction to the catalyst surface structure. For the electro-catalytic reactions that behave like this, the rate (faradaic current density) is the result of the sum of the activity of the different active sites working with very different efficiencies or abilities. In this scenario, different atomic arrangements on the catalyst surface are expected to play different roles in surface-catalyzed reactions. In this article, the functionalities that surface defects (steps) can play in the adsorption and electrocatalytic oxidation of CO on model platinum surfaces are reviewed. Surface defects are indirectly related to the up catalysis as well as to the inhibition of reaction pathways of CO electro-oxidation under very particular conditions; these surface entities are also indirectly related to restrictions for the mobility of adsorbed CO on the (111) terraced surfaces. We analyze the selective activation and deactivation of surface sites by the pH effect, and typical catalytic properties of extended surfaces and shaped-controlled nanoparticles have been discussed thoroughly. We present a model of most active sites involved in the pathways of CO2 formation from the electro-oxidation of adsorbed CO.

Культурные тренды и их особенности в материалах стратифицированных комплексов нижнего течения р. Селенги (Итанцинская впадина, юго-восточное Прибайкалье)

The proposed publication presents materials of multilayered geoarchaeological sites of the Southeastern Baikal Region, which have their own specifics of formation. Cultural horizons are included in deposits of subaerial genesis, which mainly form the surfaces of river terraces on the right bank of the main water artery of the region, the Selenga River in its lower reaches. Preliminary cultural and chronological definitions, based on the results of a typological analysis of archaeological collections, demonstrate the dynamics of the development of cultural phenomena from the Final Pleistocene to the Holocene. The main trend, characteristic of almost all the studied sites, demonstrates the “delay” of cultural innovations noted in the archaeological cultures of the eastern coast of Lake Baikal and Western Transbaikalia. As a result of a study of a series of sites in the Itantsa depression (lower reaches of the Selenga River) in the early 2000s, we revealed the stability of the morphological and technical and technological appearance of stone tools in the Final Paleolithic, Mesolithic, and Neolithic. We also noted the uniformity of the typology of the tool set made of stone and bone, and the stability of the exploitation of a single raw material base (raw materials are of the same type in terms of isotropic characteristics). These characteristics indicate a strong tradition of stone processing for more than 10 thousand years. The situation changes about 3–4 thousand years ago (the beginning of the Paleometal era), which is expressed in the expansion of the raw material base of stone raw materials, although stone processing technologies remain in the same technical traditions. Traditions of ceramic production are represented by fragments of vessels with imprints of woven net and cord, found both in the Neolithic assemblages and in the materials of the cultural horizons of the Early Bronze Age. The obtained materials can serve as initial data for the reconstruction of the development of cultural phenomena against the background of changes in the paleoclimatic situation in the Baikal region as a whole. It should also be concluded that human stay in the southeastern Baikal region is associated with climatic fluctuations towards relatively warm conditions, while the humidity indicator did not play a big role.

한반도 서해안 고창 하전리 일대 제4기 후기 해안단구의 발달

This study investigates the distribution and developmental characteristics of the late Quaternary marine terraces in Hajeon-ri, Gochang-gun in the western coast of the Korean Peninsula. The altitudes of the first and second terraces are 8~13m and 17~23m, respectively, from a regional high sea-level. As a result of OSL(Optically Stimulated Luminescence) and IRSL(Infra-red stimulated Luminescence) dating, the depositional ages of the second marine terrace are estimated as 189.53±5.19ka BP, indicating that the second terrace was formed during the penultimate interglacial period (MIS 7). The silt deposits overlying the first and second terrace surfaces are likely to have originated from paleo-tidal flat sediments based on their depositional facies and the results of geochemical analysis.

Нижнепалеолитическая стоянка-мастерская Кусимово-8 (Южное Зауралье)

Introduction. Comprehensive and efficient investigations of the earliest peopling of the Southern Urals became possible after the discovery of Mysovaya site in Abzelilovsky District of Bashkortostan (Russia). The Paleolithic materials from this site were considered mixed — Acheulean/Mousterian — or Mousterian proper. In recent years, the Lower and Middle Paleolithic site of Kusimovo-8 has been discovered nearby. This is a scattered workshop site on pebble flint outcrops within the terrace surface of the Bannoe-Sabakty paleolake. Goals. The study attempts an insight into the earliest peopling of the Southern Urals, describes and analyzes the Lower Paleolithic collection. Results. The finds were identified on the basis of technical and typological characteristics and preservation parameters. The collection comprises a total of 121 items, most of the objects made of flint pebbles and only two bifaces made of diabase. Nucleuses with patinated surfaces (19 items) are diverse enough: mainly flat cores of parallel and sub-parallel shearing are available to be quantitatively followed by radial, fan-shaped, and orthogonal cores. The tools are represented by oval and almond-shaped hand axes, cleavers, piked tools, a chopper, biface blanks, and various side-scrapers. The stratigraphy of test pits shows the presence of two cultural horizons: flint chips were found under the Middle Paleolithic cultural layer (grayish-brown loam with dolomite gravel) — 0.5 m lower in yellowish-brown loam. Paleoecological analyses of the pits attest to that yellowish-brown loam deposits can be dated to the Middle Pleistocene. Similar conditions were identified for Lower Paleolithic finds discovered at Mysovaya site. Similarity of both the sites makes it possible to conclude as to comparable ages of these collections and that they may cluster together within one Karyshkino-type industry which unites a majority of Lower Paleolithic sites across the Southern Transurals, all of them to form a specific variant of the Tayacian.

Нижнепалеолитическая стоянка-мастерская Кусимово-8 (Южное Зауралье)

Introduction. Comprehensive and efficient investigations of the earliest peopling of the Southern Urals became possible after the discovery of Mysovaya site in Abzelilovsky District of Bashkortostan (Russia). The Paleolithic materials from this site were considered mixed — Acheulean/Mousterian — or Mousterian proper. In recent years, the Lower and Middle Paleolithic site of Kusimovo-8 has been discovered nearby. This is a scattered workshop site on pebble flint outcrops within the terrace surface of the Bannoe-Sabakty paleolake. Goals. The study attempts an insight into the earliest peopling of the Southern Urals, describes and analyzes the Lower Paleolithic collection. Results. The finds were identified on the basis of technical and typological characteristics and preservation parameters. The collection comprises a total of 121 items, most of the objects made of flint pebbles and only two bifaces made of diabase. Nucleuses with patinated surfaces (19 items) are diverse enough: mainly flat cores of parallel and sub-parallel shearing are available to be quantitatively followed by radial, fan-shaped, and orthogonal cores. The tools are represented by oval and almond-shaped hand axes, cleavers, piked tools, a chopper, biface blanks, and various side-scrapers. The stratigraphy of test pits shows the presence of two cultural horizons: flint chips were found under the Middle Paleolithic cultural layer (grayish-brown loam with dolomite gravel) — 0.5 m lower in yellowish-brown loam. Paleoecological analyses of the pits attest to that yellowish-brown loam deposits can be dated to the Middle Pleistocene. Similar conditions were identified for Lower Paleolithic finds discovered at Mysovaya site. Similarity of both the sites makes it possible to conclude as to comparable ages of these collections and that they may cluster together within one Karyshkino-type industry which unites a majority of Lower Paleolithic sites across the Southern Transurals, all of them to form a specific variant of the Tayacian.

Constraining the age of Quaternary megafloods in the Altai Mountains (Russia) using luminescence

Some of the largest catastrophic outbursts of periglacial lakes known in the geological history of the Earth have been identified in the Altai Mountains. Traces of these events are recorded in the form of large terraces, predominantly composed of gravel material with numerous horizons of large boulders and blocks. Determining the age of these large-scale events is difficult due to the lack of suitable material (e.g. organics, well-bleached sand) and the specific genesis of these sediments. The results of cosmogenic radionuclide dating suggest a post-LGM age both for the source of the flood water and for different elements of the catafluvial terraces in the Chuya and Katun river valleys. Nevertheless, the age(s) of catastrophic breakthrough remains controversial. On the basis of a few IRSL ages, and geological and other evidence, some view the event as occurring around MIS 5. In this study, we investigate loess-like loams overlying the catafluvial sediments on the surface of the highest level terrace, ∼200 m above present river level. A total of 24 samples for luminescence dating were obtained, for which the OSL, IR 50 , and pIRIR 50,290 signals were measured to control the degree of signal zeroing and the dating reliability. The age of the loess in all three pits was from 0.5 ka at the top to 23 ka at the base of the loess strata. From a sand layer in the top of the catafluvial deposits, two ages of ∼85–90 ka were obtained from feldspar pIRIR 50,290 . These results provide a minimum pre-LGM age for the geomorphological surface of a major catafluvial terrace in the Altai Mountains.

Late Quaternary sedimentary record of estuarine incised-valley filling and interfluve flooding: The Manfredonia paleovalley system (southern Italy)

Multiple paleovalley systems of late Quaternary age have been widely explored in previous research from the Gulf of Manfredonia on the basis of seismic data, but only limited information is available on their proximal (onshore) segments. Through an integration of sedimentary, paleoecological (mollusks, benthic foraminifers, ostracods), and geochemical analyses from three 30-50 m-long onshore cores and a sequence-stratigraphic framework chronologically constrained by 25 radiocarbon data, we document the stratigraphic architecture of three contiguous paleovalley systems (Candelaro, Cervaro and Carapelle rivers) and their sedimentary response to Late Pleistocene valley excavation, Holocene filling and basinwide interfluve flooding. Above a prominent sequence boundary formed during the Late Pleistocene relative sea-level fall, fluvial-channel gravels and sands (lowstand systems tract) are overlain by a deepening-upward, valley-fill succession of inner-estuarine (freshwater) to outer-estuarine (brackish) muds (lower transgressive systems tract – TST). The individual valley fills are overlain by laterally extensive bay deposits (upper TST) and by a progradational succession of prodelta/delta front and offshore/shoreface deposits that reflect normal regression under highstand conditions (HST). The transition from fluvial to inner-estuary (fluvial-dominated) and outer-estuary (wave-influenced) deposits records the progressive shift in sediment provenance from Southern Apennine source rocks to a mixed composition that reflects increasing alongshore sediment contribution from northern sources via the SE-directed Western Adriatic Current. The stratigraphic surface that demarcates the transition from estuarine to bay depositional systems (lower/upper TST boundary) represents the physical prolongation of interfluvial terrace surfaces, as valley margins were flooded during the Early Holocene transgression. This surface, typically recognizable on seismic profiles at the boundary between low-amplitude and overlying high-amplitude reflectors, has no obvious lithologic signature in core. However, it can be readily identified on the basis of paleoecologic features (sharp increase in species diversity and in the proportion of marine taxa) that reveal the abrupt transition from laterally confined to unconfined settings.

Atomistic Insight into the Epitaxial Growth Mechanism of Single-Crystal Two-Dimensional Transition-Metal Dichalcogenides on Au(111) Substrate.

A mechanistic understanding of interactions between atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDs) and their growth substrates is important for achieving the unidirectional alignment of nuclei and seamless stitching of 2D TMD domains and thus 2D wafers. In this work, we conduct a cross-sectional scanning transmission electron microscopy (STEM) study to investigate the atomic-scale nucleation and early stage growth behaviors of chemical vapor deposited monolayer (ML-) MoS2 and molecular beam epitaxy ML-MoSe2 on a Au(111) substrate. Statistical analysis reveals the majority of as-grown domains, i.e., ∼88% for MoS2 and 90% for MoSe2, nucleate on surface terraces, with the rest (i.e., ∼12% for MoS2 and 10% for MoSe2) on surface steps. Moreover, within the latter case, step-associated nucleation, ∼64% of them are terminated with a Mo-zigzag edge in connection with the Au surface steps, with the rest (∼36%) being S-zigzag edges. In conjunction with ab initio density functional theory calculations, the results confirm that van der Waals epitaxy, rather than the surface step guided epitaxy, plays deterministic roles for the realization of unidirectional ML-MoS2 (MoSe2) domains on a Au(111) substrate. In contrast, surface steps, particularly their step height, are mainly responsible for the integrity and thickness of MoS2/MoSe2 films. In detail, it is found that the lateral growth of monolayer thick MoS2/MoSe2 domains only proceeds across mono-Au-atom high surface steps (∼2.4 Å), but fail for higher ones (bi-Au atom step and higher) during the growth. Our cross-sectional STEM study also confirms the existence of considerable compressive residual strain that reaches ∼3.0% for ML-MoS2/MoSe2 domains on Au(111). The present study aims to understand the growth mechanism of 2D TMD wafers.

Evolution of fluvial landscapes since the late Pleistocene at the Wangchenggang site of the Ying River Basin, Central China: Implications for the development and change of prehistoric settlements

AbstractReconstructing the evolution of fluvial landscapes is vital to our understanding of how and why early settlements used or abandoned locations in dynamic alluvial settings, especially places such as China's Central Plains where alluvial landforms have dominated since at least the late Pleistocene era. The Wangchenggang (WCG) site on the upper reaches of the Ying River is considered to be the legendary capital of the Great Yu who, according to historical documents, heroically tamed the big floods and founded the first dynasty of Xia. However, evolution of the alluvial landscape of the Holocene Ying River and its influence on the long‐term settlement change at the WCG site remains unclear. We present a detailed reconstruction of long‐term landscape evolution and settlement change at the site, based on the results of our geoarchaeological investigation, and published paleoclimate and archaeobotanical data. The results show that the region experienced an episode of extensive alluvial accretion in the late Pleistocene. From the end of the late Pleistocene to the early Holocene, the Ying River began to incise the alluvial plain, leading to the formation of the oldest terrace (T3). The middle and late Holocene in the Ying River valleys saw two episodes of alluvial aggradation between 7.7–5.4 ka B.P. (before present) and 4.5–3.8 ka B.P., respectively. Each of these events was followed by an alluvial incision, resulting in the formation of new alluvial terraces. During the historical periods, the youngest terrace T1 was formed. These cyclic changes in the regional fluvial landscape profoundly impacted the location and expansion of prehistoric settlements. During the Peiligang period (9.0–7.0 ka B.P.), the early stages of alluvial aggregation resulted in wide and shallow channels along the rivers. Early humans who relied on gathering and hunting for food chose to establish small settlements along such riverine environments. As alluvial aggradation continued in the Yangshao period (7.0–5.0 ka B.P.), they moved to a higher place, away from the rivers in the southwest, and flourished on high alluvial grounds. When a secondary terrace formed after the Longshan period (5.0–4.0 ka B.P.), people moved eastward again to build an early city on the T2 terraces and T3 terraces of the Ying River. When the water levels rose toward the terrace surfaces, they began to build moats and practiced mixed millet–rice farming. During the Eastern Zhou Dynasty (770–4256 B.C.), when the river started to down cut on a large scale, humans responded by building settlements on the lower and flat plains in the east.

A Comprehensive 4E Study on the Performance of Bifacial Solar Module Installed on Different Ground Surface Colors: An Experimental Study on a Specific Site

Abstract Solar energy will be the most sought-after source for generating electricity shortly because of its availability in abundance and pollution-free nature. Bifacial photovoltaic (PV) technology increases the power output through the albedo effect. However, the major drawback of PV-based power is that the efficiency is very low at less than 25%. The study focuses on the impact of surface color to explore the possibilities of enhancing the efficiency of solar modules considering the different terrace surfaces available in the residential region. The proposed work is one such attempt where the study is mainly focused on the impact of the surface properties on the extraction of electricity from the solar module without adopting the active techniques. A detailed study on different colors like black, green, and white is carried out. The study observed that the white surface improves the albedo effect toward the rear surface of the module, thereby improving the energy production factor (EPF) and higher life cycle conversion efficiency (LCE). It is observed that there is a 4.8% increase in the average efficiency when using white as ground cover as compared to normal reference ground. The comparative study is also carried out for various lifetime periods (T) like 10, 15, and 20 years. Calculated the exergetic cost by considering operating periods like 15, 20, 25, and 30 years with 2%, 5%, and 10% interest rates, and it is observed that after 30 years of operation at a 2% interest rate, energetic cost reached its highest value.

Surface reaction for efficient and stable inverted perovskite solar cells.

Perovskite solar cells (PSCs) with an inverted structure (often referred to as the p-i-n architecture) are attractive for future commercialization owing to their easily scalable fabrication, reliable operation and compatibility with a wide range of perovskite-based tandem device architectures1,2. However, the power conversion efficiency (PCE) of p-i-n PSCs falls behind that of n-i-p (or normal) structure counterparts3-6. This large performance gap could undermine efforts to adopt p-i-n architectures, despite their other advantages. Given the remarkable advances in perovskite bulk materials optimization over the past decade, interface engineering has become the most important strategy to push PSC performance to its limit7,8. Here we report a reactive surface engineering approach based on a simple post-growth treatment of 3-(aminomethyl)pyridine (3-APy) on top of a perovskite thin film. First, the 3-APy molecule selectively reacts with surface formamidinium ions, reducing perovskite surface roughness and surface potential fluctuations associated with surface steps and terraces. Second, the reaction product on the perovskite surface decreases the formation energy of charged iodine vacancies, leading to effective n-type doping with a reduced work function in the surface region. With this reactive surface engineering, the resulting p-i-n PSCs obtained a PCE of over 25 per cent, along with retaining 87 per cent of the initial PCE after over 2,400 hours of 1-sun operation at about 55 degrees Celsius in air.

Environmental reconstruction and formation processes in a large Mesolithic lithic scatter at Nethermills of Crathes, Aberdeenshire, Scotland

The rich resources of river valleys provided a focus for much Mesolithic hunter-gatherer-fisher activities across Europe. In Scotland there is one notable concentration of lithic evidence for this, at several locations along the River Dee in Aberdeenshire, but the environmental context of these sites has, to date, been poorly understood. Here we present evidence from excavation, repeated field-walking, flint typology, geomorphological mapping, sedimentology, pollen analysis, AMS 14C dating, OSL profiling and dating to understand the postglacial evolution of the terrace surface at the largest concentration of lithics along the River Dee, at Nethermills of Crathes. The aim was to understand in detail the environment and landscape dynamics of the site, to define whether occupation was on the active valley floor or on a terrace above the river, and whether fluvial processes had a role in site formation processes. We conclude that occupation was on a dry wooded surface, the active channel having incised below this, though to an unknown depth, and that although major floods have swept the terrace surface, the present distribution of lithics is probably largely the original distribution.

Reversible transformation between terrace and step sites of Pt nanoparticles on titanium under CO and O2 environments

Understanding the dynamic evolution of active sites of supported metal catalysts during catalysis is fundamentally important for improving its performance, which attracts tremendous research interests in the past decades. There are two main surficial structures for metal catalysts: terrace sites and step sites, which exhibit catalytic activity discrepancy during catalysis. Herein, by using in situ transmission electron microscopy and in situ Fourier transform infrared spectroscopy (FTIR), the transformation between surface terrace and step sites of Pt-TiO2 catalysts was studied under CO and O2 environments. We found that the {111} step sites tend to form at {111} terrace under O2 environment, while these step sites prefer to transform into terrace under CO environment at elevated temperature. Meanwhile, quantitative ratios of terrace/step sites were obtained by in situ FTIR. It was found that this transformation between terrace sites and step sites was reversible during gas treatment cycling of CO and O2. The selective adsorption of O2 and CO species at different sites, which stabilized the step/terrace sites, was found to serve as the driving force for active sites transition by density functional theory calculations. Inspired by the in situ results, an enhanced catalytic activity of Pt-TiO2 catalysts was successfully achieved through tuning surface-active sites by gas treatments.

Microscopic identification of stepped SiC(0001) and the reaction site of hydrogen-rich epitaxial growth

We report first-principles total-energy electronic-structure calculations, based on density-functional theory, that unveil detailed atomic structures of hydrogen-adsorbed step edges and their energetics of the silicon carbide (SiC) (0001) surface. The obtained adsorption energy of the hydrogen atom at each step reveals the microscopic reason for the step morphology on the Si-face SiC(0001) surfaces which are commonly inclined toward the $\ensuremath{\langle}11\overline{2}0\ensuremath{\rangle}$ direction in epitaxial growth. The calculated hydrogen coverages at each step and also on the surface terrace clearly identify the favorable reaction sites for the epitaxial growth, such as chemical vapor deposition (CVD) in which hydrogen is ubiquitous. The obtained results provide a firm theoretical framework to discuss the atom-scale mechanism of the epitaxial growth of SiC.

Remotely sensed time series of rapid terrace formation: Laguna del Viedma valley (Patagonia)

The Patagonian Andes were affected by a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene. Deciphering drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern terrace formation is investigated from the Laguna del Viedma valley as a modern analogue of Late Quaternary landscape evolution in Patagonia. The aim of the research was to constrain the timing of terrace formation following lake level fall of the Laguna del Viedma over a 35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from 1985-2019 to document glacier and lake changes in the study area; 2) map landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations. In total seven terrace surfaces were distinguished, with the oldest four pre-dating the ALOS PALSAR DEM (February 2000) used. Landform evidence shows the highest, and vegetated, T1 terrace surface (+40-75 m) grades to the highest lake level and was likely the elevation of the valley floor during Holocene neoglacials. Viedma glacier recession then led to a phase of lake regressions/transgressions with an overall trend of lake level fall. The DEM shows ~20 m incision from the 1985 floodplain level (T3) to the T4 level floodplain by 2000. This constrains a minimum rate of incision of 1.33 m/yr, however, the satellite time series demonstrates rapid T3 terrace formation, with evidence for mass movements contributing to lateral terrace erosion by 1986. The implications of the data are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within many large river systems of the Patagonian Andes from 42-52⁰ S. The data herein demonstrate that base level falls from sudden lake drainage events were likely a major driver of rapid landscape change in Patagonia during deglaciation.

From sink to source: Late Quaternary landscape evolution and fluvial dynamics of the Hautapu River catchment, New Zealand

Landscapes are dynamic and respond to a range of internal and external processes that influence the balance between erosion and sedimentary preservation. Documenting past depositional and erosional events is fundamental to understanding processes of landscape formation and unpacking the interplay between stream power and sediment supply. Here, we focus on a paleo-landscape reconstruction of the Hautapu River valley in New Zealand, with the aim of investigating the influence of volcanic activity, uplift, and climate on fluvial and landscape dynamics. The study area is characterized by Pliocene marine sediments superimposed by a suite of Late Pleistocene river terraces and associated cover beds. Volcaniclastic deposits of the Mataroa Formation, derived from partial collapse of the Mt. Ruapehu stratovolcano, overlie the oldest terrace level and are used to reconstruct the paleo-landscape. Depth of incision is obtained by comparing remnant terrace surfaces to present day topography. An early channel switching event after c. 125–150 ka is correlated to increased sediment supply and resultant fluvial aggradation following emplacement of the Mataroa Formation. Remobilization of volcaniclastic material resulting in blockage and channel avulsion is considered to have redirected the flow of the Hautapu River into the Mangoiwa Stream valley, evidenced by the gentle gradient, wide and more deeply incised valley geomorphology. A more recent channel abandonment event at c. 15 ka is correlated to subsidence of the Ruapehu Graben and piracy by the Whangaehu River, effectively isolating the Hautapu catchment from Mt. Ruapehu and its active source of volcaniclastic sediment. Simultaneous abandonment of the Mangoiwa Stream valley and re-establishment of the Hautapu River into its former channel is attributed to uplift, pre-existing valley morphology and strength contrasts between the valley fill and its underlying marine succession. Accelerated erosion during cold climate phases is considered to have effectively stripped regolith from deforested highlands leading to a reset of the landscape, greatly increased sediment yields and fluvial aggradation. Subsequent landscape stabilization and ongoing regional uplift during climate amelioration is associated with a reduction in sediment supply and excess stream power, leading to incision and knickpoint retreat.

Research on Automatic Identification Method of Terraces on the Loess Plateau Based on Deep Transfer Learning

Rapid, accurate extraction of terraces from high-resolution images is of great significance for promoting the application of remote-sensing information in soil and water conservation planning and monitoring. To solve the problem of how deep learning requires a large number of labeled samples to achieve good accuracy, this article proposes an automatic identification method for terraces that can obtain high precision through small sample datasets. Firstly, a terrace identification source model adapted to multiple data sources is trained based on the WorldView-1 dataset. The model can be migrated to other types of images for terracing extraction as a pre-trained model. Secondly, to solve the small sample problem, a deep transfer learning method for accurate pixel-level extraction of high-resolution remote-sensing image terraces is proposed. Finally, to solve the problem of insufficient boundary information and splicing traces during prediction, a strategy of ignoring edges is proposed, and a prediction model is constructed to further improve the accuracy of terrace identification. In this paper, three regions outside the sample area are randomly selected, and the OA, F1 score, and MIoU averages reach 93.12%, 91.40%, and 89.90%, respectively. The experimental results show that this method, based on deep transfer learning, can accurately extract terraced field surfaces and segment terraced field boundaries.

Coastal vs volcanic processes: Procida Island as a case of complex morpho-evolutive response

The island of Procida (Gulf of Naples, Italy) is a site of considerable importance from a historical, cultural, and landscape point of view. The island is located along a volcanic active area in the mid-Tyrrhenian and owes its formation to several explosive eruptions started more than 70 ka BP. Presently, the entire perimeter of the island is bordered by cliffs, often articulated in an alternation of headlands and coves, sometimes with shallow sandy beaches at the base (pocket beaches). However, the presence of different orders of submarine terraced surfaces represents a significant clue to coastal response to former sea-level stands.This paper aims at reconstructing the main coastal changes that occurred in the area during the Holocene mainly driven by the interaction between the post-glacial sea-level rise, vertical ground movements (VGMs) of volcano-tectonic origin, and wave action. The coastal sector was investigated using a multi-techniques approach including direct and indirect methods, in order to obtain a detailed geomorphological characterization of the whole study area. In particular, data from direct coastal surveys were integrated with photo-interpretation of areal and satellite photos, morphometric analysis of high-resolution DTMs from Lidar and bathymetric data, interpretation of morpho-acoustic data, archaeological, geomorphological and geological sea-level markers. The geomorphological analysis of this multidisciplinary dataset resulted in the detection of the main morphological elements interpreted as evidence of ancient seascapes. In particular, three orders of paleo-shore platforms were mapped in the underwater sector, allowing the evaluation of as many phases of relative sea-level stand, at −23.2 m, −11.2 m, and − 4.2 m MSL dated at approximately 4.0, 2.0, and 1.0 ka BP. These coastal landforms were interpreted as the main consequence of a seacliff retreat, exacerbated by volcano-tectonic intermittent subsidence that favoured their poly-cyclic formation. However, the integration between the geomorphological and meteo-marine analysis allowed discriminating differentiated cliff backwearing responses between the western and eastern coastal sectors of the island, due to a prevailing occurrence of storms from the south-western sector. The proposed methodological approach focused on a multi-temporal geomorphological analysis applied to a multi-modal dataset, aims to comprehensive reconstruct the coastal response of a volcanic high rocky coast to the complex interaction between endogenous and exogenous forcing factors during the Holocene.