Past Geomorphological Processes Research Articles

Questioning the view: Historical geography and topographical art

AbstractThis article argues that a recent resurgence of interest in topographical art has opened up a new and exciting debate about how such drawings and paintings can be used by historical geographers. This is demonstrated by a review of recent research by historical geographers, art historians, and historians, which explores how topographical art is being interrogated to examine landscape history and environmental change. Topographical views provide insights into the way in which landscapes of the past were shaped, used, and perceived. The article establishes that topographical art is increasingly used in the analysis of past geomorphological processes, which have significant implications for current landscape and heritage management. It reveals that when topographical art is correctly contextualized it can be an extremely valuable source. The artist's biography and education is of crucial importance, as well as the comparison with historical cartographies, documents, and field data. Historical geographers are particularly well placed to undertake research, which questions the artwork's accuracy and goes beyond its literal interpretation as a straightforward depiction of a place.

PARÂMETROS MORFOMÉTRICOS APLICADOS A ANÁLISE TECTONOEROSIVA EM BACIAS DE DRENAGEM / MORPHOMETRIC PARAMETERS APPLIED TO TECTONIC-EROSIVE ANALYSIS IN WATERSHEDS

O recorte espacial de bacias de drenagem é de extrema importância para a compreensão evolutiva da paisagem. E a utilização de cálculo de parâmetros morfométricos que procurem reunir evidências sobre o mecanismo evolutivo desta unidade de evolução geomorfológica vem, desde a década de 1950, sendo continuamente aplicada nestes estudos. A identificação de assimetrias de bacias e a análise de perfis de relevo transversais e longitudinais a uma bacia, bem como a observação de perfis longitudinais aos canais fluviais, subsidiam a investigação do controle tectônico na história evolutiva e o entendimento da ocorrência de processos geomorfológicos pretéritos e atuais. A avaliação da forma geométrica do perfil associada ao cálculo do Índice de Gradiente (ou Relação Declividade Extensão - RDE), vem demonstrando ser uma prática metodológica bastante útil no reconhecimento de anomalias significativas na conformação côncava de um perfil longitudinal de um canal fluvial. Para esta análise, o emprego de geotecnologias facilita e agiliza as investigações realizadas, subsidiando uma melhor espacialização das informações produzidas e, assim, auxiliando na compreensão dos mecanismos evolutivos interpretados através dos parâmetros morfométricos utilizados. Auxiliam também na compreensão das relações com informações de cunho geológico-geomorfológico, subsidiando o reconhecimento de bacias que possuem graus diferenciados de controle litológico e/ou estrutural. Deste modo, este procedimento permite reunir argumentos básicos à interpretação de possíveis (re)ajustes fluviais, caracterizando processos morfodinâmicos distintos em bacias de drenagem.

The record of postglacial environmental changes of the southern Baltic coastal zone in the sequence of fossil soils

PurposeThe studies aimed to reconstruct major phases of litho-morpho-pedogenic processes and past environmental changes in the Baltic coastal zone near Poddąbie (54°37,070′ N, 16°57,897′ E) based on physical, chemical, pollen, and fossil Cladocera analysis of the polycyclic pedocomplex.Materials and methodsThe polycyclic pedocomplex under study included seven fossil soils developed from the Early Holocene until modern times from various materials. The soils were sampled and analyzed using standard procedures in soil science to determine their physical and chemical properties. Pollen and fossil Cladocera analysis was also carried out in the examined profile. Radiocarbon dates of selected samples were also specified.Results and discussionThe studied polycyclic pedocomplex has been developed from materials of varied origin, including glaciofluvial, fluvial, aeolian, and biogenic deposits of the lake. According to the results of pollen and fossil Cladocera analysis and radiocarbon dating, this body of water has evolved from the beginning of Preboreal period to the half of Boreal. The studied soils represent various reference groups and advancement of development. They constitute relics of former geomorphological and soil-forming processes, which have taken place over the last 9500 years, including periglacial processes, wildfires, Baltic Sea shoreline changes, and aeolian activity. The last stage of the coastal relief dynamics was conditioned by the fire which took place about 1472–1637 AD. The lack of plant cover and intensive abrasion due to direct vicinity of the coastline has caused the deposition of aeolian material, which is the parent material of nutrient-poor initial soils.ConclusionsThe analysis of fossil soil development with the use of specialized research methods allowed for reconstructing the dynamics of past geomorphological processes and natural environment changes in the study area. The studied polycyclic pedocomplex constitutes a record of environmental changes taking place in the central part of the Polish Baltic coastal zone from the Early Holocene to the present day. The studied soil sequence is located within a land depression developed in place of the former water reservoir created as a result of permafrost degradation, and filled with Holocene deposits.

Geomorphological features and processes in the Sierra de Famatina, La Rioja

The Sierra de Famatina is considered the highest elevation outside the Argentine Andes Cordillera, being the General Belgrano hill, 6097 masl, the main height. This altitudinal situation favored the development of glaciers during the cold events of the cyclical Quaternary climatic fluctuations, giving shape to a territory with very complex morphologies. The aim of this contribution is to describe the current and past geomorphological processes in the vicinity of the highest sector of the Sierra de Famatina through different forms of the landscape, which put together allow the recognition of the geomorphological evolution of the region. At present, extreme weather lead to periglacial conditions above 4000 m and glacial above 6000 m, generating ice and snow patches almost without movements in flat to flat-concave sections of the watersheds, and rock glaciers, gelifluction lobes and earth hummocks in cirques, troughs and walls of valleys. Depending on the features of glacial accumulation, three cold events can be recognized, the youngest one (MIS2) with limited distribution, is restricted to the heads of troughs and cirques, from whose deposits the rock glaciers develop. The second one, observed near Puesto Tres Piedras, is represented by moraine-shaped glacier deposits above 3000 m height, and would belong to the Middle-Late Pleistocene. The oldest glacier deposits, early-middle Pleistocene, are in higher topographies. Below 3000 m, valleys are rocky and steep-sided, with permanent courses due not only to low rainfall, but mainly to the melting of the permafrost, forming important reservoirs of water.

Accuracy Assessment of Landform Classification Approaches on Different Spatial Scales for the Iranian Loess Plateau

An accurate geomorphometric description of the Iranian loess plateau landscape will further enhance our understanding of recent and past geomorphological processes in this strongly dissected landscape. Therefore, four different input datasets for four landform classification methods were used in order to derive the most accurate results in comparison to ground-truth data from a geomorphological field survey. The input datasets in 5 m and 10 m pixel resolution were derived from Pléiades stereo satellite imagery and the “Shuttle Radar Topography Mission” (SRTM), and “Advanced Spaceborne Thermal Emission and Reflection Radiometer” (ASTER GDEM) datasets with a spatial resolution of 30 m were additionally applied. The four classification approaches tested with this data include the stepwise approach after Dikau, the geomorphons, the topographical position index (TPI) and the object based approach. The results show that input datasets with higher spatial resolutions produced overall accuracies of greater than 70% for the TPI and geomorphons and greater than 60% for the other approaches. For the lower resolution datasets, only accuracies of about 40% were derived, 20–30% lower than for data derived from higher spatial resolutions. The results of the topographic position index and the geomorphons approach worked best for all selected input datasets.

Geomorphology of the Rees Valley, Otago, New Zealand

We present a 1:33,333 geomorphological map of the Rees Valley, Otago, New Zealand. The Rees River drains an area of ∼405 km2 and feeds into the head of Lake Wakatipu. This area has been affected by a range of geomorphological processes including tectonic activity, glacial erosion and deposition, mass movement, fluvial action, and base (lake) level change. Mapping was achieved by a combination of interpretation from SPOT 5 HRG satellite imagery and ground-truthing. The map presents the current distribution of landforms and sediments associated with the wide variety of contemporary and past geomorphological processes. It represents the most detailed and finest resolution geomorphological map of this region to date, and hence a number of features have been mapped and described for the first time. The map will assist on-going studies in the Rees catchment that seek to understand fluvial sediment transport and associated flood hazards, the dynamics of former glaciers, base level change associated with a drop in the level of Lake Wakatipu, and mass movement hazards.

Wind erosion and soil carbon dynamics in south-western Australia

The incidence of wind erosion and its affect on soil organic carbon content was assessed in a dryland farming system near Jerramungup, Western Australia, using remote sensing, ground observations and soil analysis. Relationships were found between the patterns of wind erosion, past geomorphic processes and an array of soil attributes. These associations can be used to identify those soils that are most susceptible to erosion and thus soil carbon loss. Despite strong evidence of relict aeolian activity associated with a previous more arid climate, the incidence of contemporary wind erosion was only partly related to past geomorphological processes. Quartzose dune sands were particularly susceptible to erosion (47% of total area eroded), whereas texture contrast soils formed on clayey, wind-formed lunettes (16%) and deeply weathered regolith were less eroded (34%). Soils formed on stripped regolith and on loamy surfaced lunettes and swales were not eroded. Wind erosion was strongly related to soil particle size distribution and surface horizon depth, only occurring on sandy surfaced soils, with 50 cm deep. The incidence of erosion markedly increased with small decreases in clay and silt contents below these thresholds. Wind erosion resulted in the loss of ∼3% of the total stock of carbon to 1 m depth or 3.6 t C ha-1 for the eroded soils. The consideration of wind erosion induced carbon loss, both from the standpoint of sustaining farmland productivity and also in producing accurate national carbon accounts, at both the project and national scales, requires resolution.

Climate change triggered sedimentation and progressive tectonic uplift in a coupled piedmont–axial system: Cuyama Valley, California, USA

AbstractChannels on the north‐facing piedmont of the Sierra Madre range in Cuyama Valley, California have alternated between three process regimes during the late Quaternary: (1) vertical incision into piedmont alluvium and older sedimentary deposits; (2) lateral erosion; and (3) sediment accumulation. The state of the piedmont system at a given time has been controlled by upstream sediment flux, regional tectonic uplift and incision of the axial Cuyama River.To better understand the timing and to attempt to interpret causes of past geomorphological processes on the Sierra Madre piedmont, we mapped the surficial geology and dated alluvial deposits using radiocarbon, cosmogenic and optical dating methods. Four primary episodes of sedimentation have occurred since ca. 100 ka, culminating in the most recent period of extensive piedmont sedimentation between 30 and 20 ka. Fill terraces in Cuyama Valley formed by piedmont sediment accumulation followed by vertical incision and lateral erosion are fairly planar and often mantle strath bedrock surfaces. Their vertical spatial arrangement is a record of progressive regional tectonic uplift and concomitant axial Cuyama River channel incision migrating up tributary piedmont channels. Subparallel longitudinal terrace profiles which have a linear age–elevation relationship indicate that multiple episodes of climatically controlled sedimentation overprints ∼1 m kyr−1 of regional uplift affecting the Cuyama River and its tributaries.Sedimentation was probably a result of increased precipitation that caused saturation landsliding in steep catchments. It is possible that increased precipitation during the Last Glacial Maximum was caused by both continental‐scale circulation pattern reorganization and increased Pacific storm frequency and intensity caused by ‘early warming’ of nearby Pacific Ocean surface waters. Older episodes of piedmont sedimentation are difficult to correlate with specific climate regimes, but may correlate with previous periods of increased precipitation. Copyright © 2007 John Wiley & Sons, Ltd.