Landscape Evolution

Studies on denudation rates can provide insight into the influence of climate change, tectonics, and human activities on landscape evolution. Research performed in Central Italy has shown considerable spatial variability of denudation rates in the major river basins. These studies have focused mainly on the Tyrrhenian side of the Italian peninsula, where Plio-Pleistocene marine deposits filling NW–SE elongated sedimentary basins have been uplifted during the Quaternary up to several hundreds of meters above present sea level. Small sub-catchments developed on clays are affected by sharp- and/or rounded-edged badlands (i.e. calanchi and biancane), representing denudation “hot spots” in the present-day morphoclimatic framework.In this paper, we analyze the relationships between indirectly estimated denudation rates at the catchment scale and field monitoring data at the hillslope scale. We attempt to better understand and quantify all hillslope processes that contribute to seasonal variability of denudation, to help with predicting the net input from “hot spots” to the overall estimated sediment yield at the basin outlets. At the hillslope scale, we discuss, in particular, the variability of denudation rates at calanchi and biancane badlands as a function of their different morphoevolution.

The Warratta Inlier is located in northwestern New South Wales, approximately 20 km south of Tibooburra. The Inlier is bound on its northeastern side by the Warratta Fault and it has been suggested that this is an extension of the Olepoloko Fault (Stevens 1985), a major terrain boundary between the Thomson Fold Belt and the Lachlan Fold Belt of the Tasmanides. This study incorporated potential field geophysics and regolithlandform mapping to determine possible models for the landscape evolution of the area, based on ...

Geomorphic models such as the glacial buzz saw and denudational unloading and understanding the significance of active tectonics on geomorphic systems can be elucidated by quantitatively defining rates of erosion and sediment transfer in active mountain systems. To this end, we examine the topographically and morphometrically asymmetrical Ladakh Range to quantify the significance of tectonic influence on geomorphic systems. Morphometric analysis and10Be cosmogenic radionuclide dating of 13 fluvial sediment samples from active channels was undertaken in 6 catchments to define erosion rates. North facing catchments of the central Ladakh Range have erosion rates of 0.056±0.012 mm/yr and 0.074±0.011 mm/yr, while south facing catchments have rates of 0.020±0.003 mm/yr, 0.020±0.003 mm/yr, and 0.039±0.008 mm/yr. Rates of erosion in north facing catchments are approximately two times higher than rates of erosion in south facing catchments. This data confirms that the tectonic tilting of the Ladakh Range and active rock uplift (~ 1 mm/yr) on the northern side of the range has had a significant impact on the rate of erosive geomorphic processes. However, the increased erosion on the northern side of the range is not keeping pace with rock uplift on the northern side of the range. Morphometric analysis shows that the maximum and average elevations increase at nearly the same rate across the Ladakh Range with higher elevation on the northern side. This precludes the possibility of long-term denudational unloading from having a significant feedback into the tectonic tilting of the range.

The Inman River Catchment sits within a well-defined geomorphological feature on the southern part of Fleurieu Peninsula, a relict of an ancient glaciation, which eroded a large east-west trending bedrock depression across Fleurieu Peninsula known as the ‘Inman Trough’.  The Inman Catchment contains a unique geology and distinctive landforms, some of which have been recognised as being of international scientific significance.  The key land-forming processes responsible for the location and setting of the catchment were related to a glaciation of Antarctic proportions, which occurred about 300 million years ago, during Permian times, when Antarctica was welded onto southern Australia.  As the ice melted great thicknesses of sediments were deposited onto the glaciated bedrock floor.  These glacigene sediments are currently being eroded by running water, re-exposing parts of the ancient glacial landscape, and moulding the present landscape. 

A long geological history, which established the ancient bedrock floor of the peninsula, preceded the Permian glaciation.  The oldest rocks that occur on the northern boundary of the catchment are part of the 2 billion year-old core of the region.  The remaining hard rocks forming the floor and sides of the catchment were originally sediments more than 24 km thick, deposited in ocean basins during Proterozoic and Cambrian times (more than 500 million years ago).  These sediments were transformed by heat and pressure, and folded about 500 million years ago to form a huge mountain range of Himalayan magnitude, into the base of which granites were intruded.  Over the ensuing 200 million years this mountain range was so severely eroded that during the Permian ice age the oldest, deepest rocks in the mountains were exposed at the surface.

After the retreat of the Permian ice sheet the catchment was subjected to prolonged weathering and erosion over many millions of years, producing a landscape of low relief that was intensely weathered to depths exceeding 70 m.  The progressive uplift of this surface of low relief and its ongoing weathering and erosion has produced the high plateau surface on the margins of the catchment such as at Spring Mount.  Throughout this early geological history Australia and Antarctica were joined together as part of the ancient super-continent Gondwana: they were the last of the continents to separate about 43 million years ago, following which there were tectonic movements and incursions of the sea.

The sea inundated parts of the southern Australian coastline several times from about 40 million years ago and tectonic activity formed the marine St Vincent and Murray Basins. Marine incursions onto Fleurieu Peninsula deposited fossiliferous limestones, remnants of which occur at high levels in the Myponga, Upper Hindmarsh Valley and Waitpinga areas.  Ongoing earth movements progressively uplifted the Mount Lofty Ranges following the rifting of Australia and Antarctica, elevating the fossiliferous limestones up to 240 m above sea level as they did so.  Throughout the tectonic uplift, rivers, streams and weathering processes continued to mould the landforms in the catchment.

Over the past 2.6 million years of the Pleistocene, global sea level fluctuated dramatically with sea level falling to about 125 m below present sea level and returning to near present sea level about 30 times.  Only the last major sea level fluctuation (125,000 years ago) is recorded in the catchment, producing river terraces and stranded shorelines in the lower reaches of the Inman River.  During the Holocene, the last 11,500 years of Earth history, alluvial sediments accumulated in channel bottoms forming floodplains and swamps.

The arrival of humans witnessed some major changes in the landscape.  Over many thousands of years Aboriginal occupants actively managed the landscape, particularly through the use of fire. This had significant impacts, with plants and animals adapting to the mosaic-burning regime, which produced open parkland environments in places.  These landscapes were very attractive to the first European settlers in the early 1840s but the practices that were implemented to establish settlements supported by agriculture, albeit initially on a comparatively small scale, severely disrupted the pre-existing landscape ‘equilibrium’. Clearing of vegetation, cessation of burning practices, single-furrow ploughing of land areas, and the introduction of livestock, rabbits and weeds triggered significant changes.  Thus, new landforms were generated as the landscapes adapted.  Some obvious expressions of change were soil nutrient depletion, various forms of erosion (slumping, gullying, stream incision, stream bank collapse) and alluviation.  Changes to hydrology and water quality in the catchment were additional consequences. 

The last few decades have witnessed progressive changes in landuse, with current land management strategies being focused on soil and land conservation, erosion repair through revegetation and watercourse controls, and the eradication of feral animals and plants.  Thus, the agricultural regime which triggered the disruption of pre-European settlement landscapes throughout the catchment has, over more than 100 years or so, progressively changed to a new agricultural landuse regime under which the dramatic earlier erosional features have been progressively stabilised and ‘healed’.

The coastal plain located between Figueira da Foz and Nazaré (western central Portugal) has a general low slope towards west, with altitudes below 200 m, and constitutes an important geomophological unit that is usually called “Littoral Platform”. At north, east and south, the platform is limited by the limestones relieves of the Serra da Boa Viagem – Verride arc, Sicó Massif and Estremenho Massif.
These relieves are characterized by high slope values and altitude > 200 m. The fluvial incision produced narrow valleys, that in the study area comprise the distal sectors of the Mondego and Lis drainage basins. Regionally six territorial units were distinguished which, given the characteristics of the natural systems and the development of human activities, determine different areas of risk: the limestone hills, sandy hills, floodplains, coastal plain, littoral and the probable neotectonic structures.
The limestone hills are particularly sensitive to geomorphological risks (landslides), the sandy hills are vulnerable not only to geomorphological risks (landslides, streams, erosion by land and water) but also to forest fires, alluvial plains are vulnerable to floods and flooding, coastal plain and its field of eolian dunes vulnerable to forest fires, the coast with high vulnerability to erosion of different types according to morphology of the coast and, finally, the probably active tectonic structures, particularly
those that are related to diapiric structures, are a source of seismic risk. The detailed geomorphological maps created were a very important tool for the localization and identification of the mineral resources outcrops and to improve the susceptibility maps also created.

The chapter focus is on spatial aspects of erosion processes and their modeling using Geospatial Information Science principles and tools. The mathematical, statistical and physics foundations of erosion models are introduced and simplified cases, suitable for Geographic Information System (GIS) implementation are derived. Coupling of complex models with GIS is discussed and examples of GIS implementation of simple and advanced models is presented. Regression and statistical modeling approaches are also included. The concepts and methods are illustrated using several case studies at different scales, levels of detail and complexity. Visualization of the modeling results includes dynamic surfaces and innovative Tangible Geospatial Modeling System. Future directions in geospatial erosion modeling are discussed, reflecting the new developments in mapping and monitoring technologies.

Keywords: geospatial modeling, landscape evolution, regression analysis, rills, soil erosion, sediment routing

The Brecon Beacons in southern Wales is a large upland area (900 km2) close to the periphery of the former British–Irish Ice Sheet. The geomorphology of the Brecon Beacons highlands and surrounding areas was mapped using satellite imagery and a digital elevation model (DEM). A fragmentary pattern of glacial lineations is inferred to represent ice build-up in the mountains. A more

Human habitation patterns are constrained by natural resources and processes. Any regional archaeological project must therefore first determine the primary resources provided by the natural setting, including the availability of fresh water, arable land, mineral deposits, building stones, and natural harbors, and, second, investigate the geological processes that may have distorted the original archaeological record, including erosion, deposition, tectonic movement, and coastal progradation and regression. Only when the quality and quantity of these factors are known will archaeological field projects be able to establish site size, function, and duration and reconstruct and interpret the historic interrelation between human habitation and landscape evolution.

The Hangay Mountains are a high-elevation, low-relief landscape within the greater Mongolian Plateau of central Asia. New bedrock apatite (U-Th)/He single-grain ages from the Hangay span ~70 to 200 Ma, with a mean of 122.7 ± 24.0 Ma (2σ). Detrital apatite samples from the Selenga and Orkhon Rivers, north of the mountains, yield dominant (U-Th)/He age populations of ~115 to 130 Ma, as well as an older population not seen in the Hangay granitic bedrock data. These low-temperature data record regional exhumation of central Mongolia in the Mesozoic followed by limited erosion of <1-2 km since the Cretaceous, ruling out rapid exhumation of this magnitude associated with any late Cenozoic uplift. Apatite (U-Th)/He age elevation patterns suggest long-term thermal stability of the upper crust and thermal model inversions require late Mesozoic uplift, spatially variable exhumation, and/or relief evolution to produce the observed cooling ages in the Hangay. Regionally, modeling suggests reduction of topography in the Jurassic followed by relief growth that was completed by the mid-Cretaceous. These results support Mesozoic topographic evolution and relative stability of the landscape throughout the Cenozoic with very little subsequent exhumation. Alpine cirques and intact moraines are indicative of more recent, modest climate-driven erosion in the higher peaks of the western Hangay. These data reinforce the notion that in the absence of strong tectonic or climate forcing, erosion is limited and remnant landscapes can persist over tens to hundreds of millions of years in a state of disequilibrium. Plain Language Summary The Hangay Mountains in central Mongolia are a mysterious area of high topography within central Asia. The Hangay topography has typically been thought of as a more youthful feature, uplifted and created in the last 20-30 million years. The geochemical and geologic data presented here instead suggest that this is a very old mountain landscape that has persisted for nearly 100 million years. Numerical modeling performed for central Mongolia advocates for a scenario where topography was created in the Mesozoic and over the past 100 million years has undergone very minimal erosion due to a persistently arid climate and minimal plate tectonic activity.

The privileged location of Venezuela along an active interplate deformation belt, despite of being a "so-called" developing country, has led to a long paleoseismic tradition as attested by 45 trench assessments since 1968. Since then, a first 2-trench study was carried out by the American Woodward-Clyde company across the Oca fault at Sinamaica. Since 1980, all further paleoseismic studies have been performed by FUNVISIS and the Uribante-Caparo hydroelectric project (southern Mérida Andes) became their first assessment where 22 huge trenches were bulldozer-dug. Except for these Compañía Anónima de Administración y Fomento Eléctrico (CADAFE) financed trenches and two others, all other assessments were for Petróleos de Venezuela S. A. —PDVSA-. In this paper, geographic and geologic factors, as well as logistic limitations, conditioning success in paleoseismic studies by trenching, shall be discussed based on the Venezuelan experience developed over the years. The scientific contribution of this approach refer to: confirmation of Holocene fault activity, slip-per-event and average slip rate of a given fault (or segment), seismic potential (repeat of maximum credible earthquakes) of known faults, fault segmentation, fault interaction as consequence of stress loading by stick-slip on contiguous faults, time-space distribution of seismic activity along a given tectonic feature, seismotectonic association of historical earthquakes and landscape evolution on the short term and its implications on the long-term evolution (poorly discussed since this is really part of the field of Neotectonics). In recent years (since 1999), a new approach has been introduced in Venezuela consisting in complementing the seismic history derived from trenching studies with the evaluation of seismically induced perturbations in the continuous Quaternary sedimentary record of (either active or fossil) lakes. The future of this discipline in Venezuela heads to more trenching and lake coring in order to gather more data on the previously mentioned aspects. Other paleoseismic approaches have been developed very little in Venezuela since either climate or the geodynamic setting do not favor their application.