Biography:

In the past Jasper Knight has collaborated on articles with Raeesa Moolla and James Goff. One of their most recent publications is Chapter Six - Geomorphological Field Mapping. Which was published in journal .

More information about Jasper Knight research including statistics on their citations can be found on their Copernicus Academic profile page.

Jasper Knight's Articles: (14)

Chapter Six - Geomorphological Field Mapping

AbstractThis chapter discusses the principles and applications of geomorphological field mapping, using areas of upland terrain for example, where the presence of well-defined landforms either demonstrates ongoing geomorphic activity associated with specific process–response systems or relates to the former operation of cold climate processes associated with past climate change. In such environments, landform assemblages can be linked together through landsystems, which describe the spatial and temporal relationships of distinctive landform and sediment assemblages that correspond to different formational environments and climate regimes. Geomorphological field mapping of such landform assemblages is therefore an important technique in identifying and interpreting landscape patterns and geohazards, and determining the sensitivity of landscapes to external forcing by climate change or human activity.

The environmental significance of ventifacts: A critical review

AbstractVentifacts (wind-abraded clasts or rock surfaces) are common features of many terrestrial hot and cold deserts, coastal, periglacial and mountain environments, as well as on Mars, and have a long history of investigation. This review paper discusses some of the main themes in terrestrial ventifact research including their formation and geomorphic controls. The varied morphological forms of ventifacts in terrestrial environments, and their environmental significance as indicators of past and present wind direction and sediment mobility, are critically evaluated. Future research directions are identified.

Sub-ice shelf deposition during the late Devensian glaciation in western Ireland

AbstractGlacigenic sediments preserved around the margins of Clew Bay, western Ireland, record deposition in a tidally-influenced, sub-ice shelf environment during the late Devensian glaciation (∼ 21–13 14C kyr). Thick, massive to normally-graded glacial diamictons (tills) are interbedded with laminated to massive silt and clay beds. These sediments interbed with each other on scales ranging from millimetres to metres in a generally shallowing-up sequence associated with a decrease in accommodation space. Isolated dropstones and a downward-going clastic dike are also observed. These structures and sediments reflect a waterlain environment with rhythmically-varying levels of water energy and sediment supply. Tidally-driven uplift and downdraw of a retreating ice shelf is a likely control on sedimentation patterns, and glacial dynamics, of this sensitive, Atlantic-facing ice margin.

Boulder dynamics on an Atlantic-facing rock coastline, northwest Ireland

AbstractThe rock coast of northwest Ireland comprises steep cliffed headlands and more open coastal sections where bedrock shore platforms are developed. Many shore platforms are overlain by boulders; the locations on the platform from which boulders are derived are marked by ‘holes’ of fresh and unweathered rock surfaces that are not, or are poorly, covered by lichen. These areas of boulder detachment are termed sockets. This paper examines the mapped distributions and physical properties of boulders, sockets and shore platform context of an Atlantic-facing granite shore in County Donegal, northwest Ireland. Results from Schmidt hammer rebound tests show statistically-significant differences in rebound values between areas inside and outside of sockets and between sockets and boulders. Based on their distributions and physical properties, relationships between sockets and boulders are explored. We calculate that sockets are formed rapidly by winter storms but are also rapidly weathered over c. 5 years, becoming indistinguishable from the surrounding bedrock platform. We argue that, in contrast to some studies, boulders here were formed during recent winter storms (episodically during the last 150–200 years) rather than by more ancient waves or by tsunamis. However, a significant proportion of boulders (c. 20%) are morphometrically dissimilar to sockets; we argue that these were formed by infrequent and unusually-powerful waves that stripped whole bedrock sheets off the platform surface and which detached boulders from the lower shoreface.

Processes of soft-sediment clast formation in the intertidal zone

AbstractMuddy soft-sediment clasts found on the sandy beach at Formby Point, north-west England, are formed by wave erosion of late Holocene intertidal sediments that are exposed during summertime ridge and runnel development. Break-up processes of the intertidal sediments are strongly controlled by pre-existing bedding and surface desiccation cracks. Erosion of the intertidal sediments and formation of soft-sediment clasts contributes to the provision of fines into this dominantly sandy environment, but loss of the archaeologically significant Holocene intertidal sediments is a potentially important management issue along this coast.

The geomorphology and sedimentology of eskers in north-central Ireland

AbstractEskers are common glacial landforms in Ireland and form regionally-extensive networks that reflect stages of ice retreat of this sector of the late Devensian (Weichselian) British–Irish ice sheet. However, the sedimentary structures and composition of these eskers are poorly known, despite being able to offer valuable insight into subglacial hydrological processes during deglaciation. This study presents detailed morphological and sedimentary evidence from six esker systems in north-central Ireland, where adjacent and interacting ice domes were characterized by changes in ice-bed thermal and hydrological properties as well as significant ice dome centre migration. Morphologically, esker ridges in this area vary in length, size and continuity, with some esker systems ascending over hills (thus crossing watersheds) whereas other systems are confined to basin settings. Esker systems commonly appear to feed terminal outwash and glaciolacustrine deltas, but several systems do not show a clear terminus. The internal sediments within eskers vary from concentrically-bedded sands and gravels formed within enclosed tunnels, to interbedded sands, gravels and diamictons, occasionally with water-induced soft-sediment deformations, that are likely formed in interlobate settings. In contrast with some previous glacier models that assume that esker systems are isochronous and were formed in solely subglacial settings, the esker systems described here are interpreted as being of different ages, formed in variously subglacial to ice-marginal settings, and thus cannot be used as a single snapshot of the disposition of ice domes during stages of late Devensian ice retreat.

Assessment of occupational exposure to BTEX compounds at a bus diesel-refueling bay: A case study in Johannesburg, South Africa

Highlights•Benzene concentrations are above international occupational exposure limits.•There is adiscrepancy between national and international occupational exposure limits (OELs).•O-xylene and benzene are the most abundant species of total BTEX at the site.•Benzene levels are a concern for occupational exposure at a diesel refuelling bay.

Short communicationAnthropogenic disruption to the seismic driving of beach ridge formation: The Sendai coast, Japan

Highlights•The Tōhoku-oki earthquake led to seismogenic landslides inland.•Seismogenic sediments are reworked through river systems to the coast.•River dams are capturing these sediments, reducing sediment supply to the coast.•Reduced coastal sediment supply is increasing tsunami risk.•Engineering of river systems is making coastal engineering more necessary than ever.

Formation of desert pavements and the interpretation of lithic-strewn landscapes of the central Sahara

Highlights•Palaeosols and desert pavements are common in the central Sahara.•Soil pedosequences reflect erosion (arid) and accumulation (humid) periods.•Desert pavements are condensed stratigraphies, reflecting mixed ages.•Surface lithic scatters are strongly affected by subaerial weathering .

Geomorphic evidence for active and inactive phases of Late Devensian ice in north-central Ireland

AbstractIn the Clogher Valley, north-central Ireland, subglacial and proglacial landforms provide evidence for phases of active and inactive subglacial and ice-marginal processes during the Late Devensian (Weichselian) glaciation (∼22–13 kyr BP). Patterns of subglacial Rogen moraines and drumlins record east to west ice flow along the valley axis during maximal ice stages. Eskers, superimposed upon the Rogen moraines and drumlins, record later west to east ice flow and mark the first stages of ice retreat. Areas of large, ice-marginal, non-aligned ridges and mounds are separated by more extensive areas in which no deglacial landforms or sediments are present. The non-aligned ridges and mounds do not show a dominant directional signature, have intricate basal outlines, steep slopes and high relief (< 25 m), and are morphologically associated with meltwater channels and deep enclosed depressions (kettleholes). The ridges and mounds are interpreted as ice-marginal moraines formed by a combination of proglacial thrusting and gravity processes (high sediment mobility) during the melting out of buried ice blocks. An alternative model may involve sediment transport by glacially-driven, groundwater fluxes forming so-called ‘extrusion moraines’. Both models suggest that basal ice was polythermal in character and that alternating active (thrusting) and passive (stagnation) processes at the ice margin took place during overall westward ice retreat.

Tracing recent environmental changes and pedogenesis using geochemistry and micromorphology of alluvial soils, Sabie-Sand River Basin, South Africa

Highlights•We studied alluvial soils in the Sabie-Sand River Basin.•Soils are weakly developed with lithological discontinuities.•Soil geochemistry and micromorphology provided evidence of environmental change.•Flood events affected soil development in the Sabie-Sand River Basin.

Glacial sedimentary evidence supporting stick-slip basal ice flow

AbstractLast Glacial (Late Devensian) subglacial sediments in the southern Sperrin Mountains, north central Ireland, comprise tabular bedrock rafts which are interbedded with diamicton (till) and brecciated bedrock and separated by glaciotectonic shears. Bedrock rafts and diamicton beds alternate laterally and vertically in the profile, suggesting the ice-bed interface was chequered with both high-strength (rock rafts) and low-strength (diamicton) patches during accumulation of the sediment pile. The overall facies arrangement is interpreted qualitatively as reflecting stick-slip basal ice flow and is related to the redistribution of free subglacial meltwater at the ice-bed interface. It is inferred that stick phases occur over bedrock rafts as meltwater migrates to lower-pressure regions, infilling shallow cavities on the surrounding diamicton surface. Slip occurs when porewater pressure increases and the meltwater layer backfills across bedrock raft surfaces, causing ice-bed uncoupling. The presented field evidence suggests a stick slip rather than pervasive subglacial deformation model may be a better approximation for the flow of parts of the Late Devensian mid-latitude ice sheets.

Pleistocene glaciations in Ireland

AbstractA literature survey and data from recent investigations are used to reconstruct ice limits in Ireland during the last (Midlandian) and penultimate (Munsterian) cold periods which are correlated with Marine Isotope Stages (MIS) 2-5d (Weichselian) and 6-8 (Saalian) respectively. Evidence for Munsterian ice limits and flow directions is equivocal and based mainly on erratic carriage and the presence of striae and subdued glacial landforms found outside well-marked Midlandian end moraines. Ice extent and flow direction is known only from the late Midlandian (MIS 2; 24-10 kyr BP) although ice may well have been present in the early Midlandian (MIS 3-5d; 24-117 kyr BP). Six late Midlandian glacial stages are identified on the basis of morphosedimentary and dating evidence, and patterns of subglacial bedforms including drumlins and Rogen moraines. Previous late Midlandian glacial models are well-established but are generally based on incomplete and/or erroneous datasets, are not age-constrained, and do not consider time-transgressive sedimentation and landform-shaping events.Recent work shows that repeated ice advance-retreat cycles (oscillations) occurred during the late Midlandian. Oscillations resulted in stratigraphically superimposed, overprinted and cross-cut landform and sediment patterns that record ice activity throughout the glacial cycle. Additionally, subglacial bedforms previously unrecorded in the British Isles, such as flow-transverse ridges (Rogen moraines), are also present. Late Midlandian ice oscillations in Ireland occurred in tempo with millennial-scale changes in North Atlantic climate, suggesting connection to hemispheric shifts of the ice-ocean-atmosphere system.

ViewpointLimitations of uniformitarianism in the Anthropocene

AbstractFor many decades, studies in physical geography, geomorphology, sedimentology and stratigraphy have used uniformitarianism as a guiding principle by which to interpret environmental and land surface changes over different spatial and temporal scales. In this paper we argue that, as the Anthropocene proceeds and Earth systems increasingly move away from the mix of geomorphological processes typical of interglacial periods, significant limitations arise regarding the use of uniformitarianism as a principle by which to interpret Earth surface systems of the present and future. We argue that looking to changes in linked climate and land-surface processes of past interglacial periods is increasingly inappropriate in evaluating the impacts of ongoing climate change on Earth surface processes of the Anthropocene in which complex human-induced land surface feedbacks are increasingly important. We argue that all geoscientists need to critically reconsider whether the long-held assumptions of uniformitarianism are useful in the Anthropocene era.

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