scholarly journals Emergent simplicity despite local complexity in eroding fluvial landscapes

Geology ◽  
2021 ◽  
Author(s):  
Gareth G. Roberts
Keyword(s):  
Current Understanding ◽  
Field Observations ◽  
Local Conditions ◽  
Erosion Rates ◽  
Local Complexity ◽  
Small Scales ◽  
River Profiles ◽  
Topographic Evolution

Much of our current understanding of continental topographic evolution is rooted in measuring and predicting the rates at which rivers erode the landscape. Flume tank and field observations indicate that stochasticity and local conditions play important roles in determining rates at small scales (e.g., <10 km, thousands of years). Obversely, preserved river profiles and common shapes of rivers atop uplifting topography indicate that erosion rates are predictable at larger scales. These observations indicate that the response of rivers to forcing can be scale dependent. I demonstrate that erosional thresholds can provide an explanation for why profile evolution can be very complicated and unique at small scales yet simple and predictable at large scales.

scholarly journals Emergent simplicity despite local complexity in eroding fluvial landscapes

2021 ◽  
Author(s):  
Gareth Roberts
Keyword(s):  
Field Observations ◽  
Local Conditions ◽  
Erosion Rates ◽  
Local Complexity ◽  
Small Scales ◽  
River Profiles ◽  
Topographic Evolution

Much understanding of continental topographic evolution is rooted in measuring and predicting rates at which rivers erode. Flume tank and field observations indicate that stochasticity and local conditions play important roles in determining rates at small scales (e.g. < 10 km, thousands of years). Obversely, preserved river profiles and common shapes of rivers atop uplifting topography indicate that erosion rates are predictable at larger scales. These observations indicate that the response of rivers to forcing can be scale dependent. Here I demonstrate that erosional thresholds can provide an explanation for why profile evolution can be very complicated and unique at small scales yet simple and predictable at large scales.

scholarly journals Seasonal variability of hydrodynamics in the Vistula Estuary in 1994

2007 ◽  
Vol 36 (4) ◽  
Author(s):  
Małgorzata Robakiewicz
Keyword(s):  
Wind Direction ◽  
Water Body ◽  
Seasonal Variability ◽  
River Mouth ◽  
Meteorological Conditions ◽  
Field Observations ◽  
Mixing Processes ◽  
Local Conditions ◽  
Open Sea ◽  
Region Model

Seasonal variability of hydrodynamics in the Vistula Estuary in 1994The Vistula Estuary is a coastal water body boasting free connection with the open sea, where mixing processes of marine and fluvial waters are maintained by local conditions. Based on results from a hydrodynamic model, applied to represent conditions in the year 1994, and using salinity as a tracer, it was found that fluvial water has a tendency to spread westward from the river mouth. This is in contradiction with the dominant wind direction in the region. Model results confirmed field observations of specific hydrological and meteorological conditions required to transport fluvial water northward, towards the Hel Peninsula.

Evaluating the effect of variable lithologies on rates of knickpoint migration in the Wutach catchment, southern Germany

2020 ◽  
Author(s):  
Andreas Ludwig ◽  
Wolfgang Schwanghart ◽  
Florian Kober ◽  
Angela Landgraf
Keyword(s):  
Transient Response ◽  
Stream Power ◽  
Main Trunk ◽  
Southern Germany ◽  
Level Change ◽  
Base Level ◽  
Bulk Parameter ◽  
River Profiles ◽  
Topographic Evolution ◽  
Headward Erosion

&lt;p&gt;The topographic evolution of landscapes strongly depends on the resistance of bedrock to erosion. Detachment-limited fluvial landscapes are commonly analyzed and modelled with the stream power incision model (SPIM) which parametrizes erosional efficiency by the bulk parameter K whose value is largely determined by bedrock erodibility. Inversion of the SPIM using longitudinal river profiles enables resolving values of K if histories of rock-uplift or base level change are known. Here, we present an approach to estimate K-values for the Wutach catchment, southern Germany. The catchment is a prominent example of river piracy that occurred ~18 ka ago as response to headward erosion of a tributary to the Rhine. Base level fall of up to 170 m triggered a wave of upstream migrating knickpoints that represent markers for the transient response of the landscape. Knickpoint migration along the main trunk stream and its tributaries passed different lithological settings, which allows us to estimate K for crystalline and sedimentary bedrock units of variable erodibility.&lt;/p&gt;

scholarly journals MORPHODYNAMIC OF BEACH SCARPS ON A MACROTIDAL COAST DURING EXCEPTIONAL WATER LEVEL EVENTS (NORMANDY, FRANCE)

2012 ◽  
Vol 1 (33) ◽  
pp. 11
Author(s):  
Yoann Bonte ◽  
Franck Levoy
Keyword(s):  
Water Level ◽  
Conceptual Models ◽  
High Tide ◽  
Weather Conditions ◽  
Qualitative Description ◽  
Field Observations ◽  
Fair Weather ◽  
Physical Processes ◽  
Data Set ◽  
Local Conditions

Although there are numerous studies on the morphology and physical processes affecting the dune's scarp and many conceptual models describing beach scarps on microtidal and mesotidal environments (Sunamura, 1985a ; Short,1999), really quantitative informations about the beach scarp formation is lacking, especially along tidal environments where the tide controls the level of wave attack. However, Sherman and Nordstrom(1985) give a qualitative description of beach scarp formations and evolution based on field observations but without data set. The coast of Calvados (Normandy, France) is a fine example of a macrotidal coast, where beach scarps have been often observed. Along macrotidal beaches, the formation of a berm is classically observed during fair weather conditions which contribute to stabilize the coastline. During stormy conditions, the low atmosphere pressure, short waves and onshore winds cause an increase of the water level, which during spring tides, increases the high tide water level time action. Consequently, the natural berm protecting the dune foot, or sometimes a seawall foot, is threatened by erosion and often destroyed. The goal of this study is to quantify the beach scarp destruction (foot and crest scarp retreat speed, eroded volume...) in relation with the hydraulic and morphologic local conditions.

scholarly journals The Physical Processes involved in the Melting of Icebergs (Invited paper)

1980 ◽  
Vol 1 ◽  
pp. 97-101 ◽  
Author(s):  
Herbert E. Huppert
Keyword(s):  
Current Understanding ◽  
Field Observations ◽  
Ambient Water ◽  
Physical Processes ◽  
Water Line ◽  
The Third ◽  
Short Summary ◽  
Melt Water ◽  
Wave Induced ◽  
Horizontal Layers

The causes of iceberg deterioration can be discussed under three broad headings: wave-induced melting at the water line; breaking; and melting at the top, bottom, and sides. A short summary of current understanding under the first two headings is presented. It is then argued, under the third heading, that the melt rate at the sides of a tabular Antarctic iceberg is likely to exceed that at the top and bottom. The behaviour of the entraining plume which forms at the side of an iceberg when it melts in water of uniform salinity is outlined. Another form of convection, occurring when the ambient water is stratified, is then described; in this case the melt water spreads out in a series of almost horizontal layers. Finally, field observations on iceberg melting are discussed.

scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2018 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology, or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in elevations of these segments are used to identify knickpoints and knickzones, and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows extraction of varying knickpoint morphologies, including stepped, positive slope-breaks (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations, and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2019 ◽  
Vol 7 (1) ◽  
pp. 211-230 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in the elevations of these segments are used to identify knickpoints, knickzones and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows for the extraction of varying knickpoint morphologies, including stepped, positive slope-break (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

Olivine enrichment in dehydration veins in serpentinites by reactive fluid flow

2021 ◽  
Author(s):  
Konstantin Huber ◽  
Johannes C. Vrijmoed ◽  
Timm John
Keyword(s):  
Fluid Flow ◽  
Subduction Zones ◽  
Water Cycle ◽  
Oceanic Lithosphere ◽  
High Abundance ◽  
Field Observations ◽  
Reactive Fluid ◽  
Ligurian Alps ◽  
Small Scales ◽  
Reactive Fluid Flow

&lt;p&gt;Serpentinite dehydration in subduction zones plays an important role in Earth&amp;#8217;s deep water cycle. In order to keep this water cycle in balance, an efficient rock dehydration mechanism at depth is needed to keep pace with loss of ocean water due to subduction of hydrated oceanic lithosphere. Field observations in non-deformed meta-serpentinites in Erro Tobbio, Ligurian Alps, show that serpentinite dehydration at depth occurs by a channelized vein network rather than pervasive flow. The mineral assemblage in the veins is characterized by a high abundance of metamorphic olivine. Pl&amp;#252;mper et al. (2017) showed that on small scales (&amp;#956;m-mm) the formation of these veins is controlled by intrinsic chemical heterogeneities in the rock. Field observations suggest that on larger scales the fluid escape is governed by mechanical processes such as hydraulic fracturing. On small scales, where dehydration is chemically controlled, reactive fluid flow is an important process because changes in the fluid chemistry may trigger or hinder further dehydration reactions in the rock. Because of its high solubility and high abundance as a rock forming component, Si might be a key metasomatic agent for first-order effects on the dehydration process.&lt;/p&gt;&lt;p&gt;Following the approach of Beinlich et al. (2020) we extended the model of Pl&amp;#252;mper et al. (2017) to a reactive fluid flow model for serpentinite dehydration that accounts for the Si content of the fluid. As input for our model we use mineral chemical data of non-dehydrated serpentinites from the Mirdita ophiolite in Albania that are representative for serpentinized oceanic lithosphere that enters a subduction zone, hence has not experienced any subduction-related metamorphic processes. The results of our model suggest that the high abundance of metamorphic olivine observed in the Erro Tobbio meta-serpentinites hence the purification towards a olivine-dominated assemblage is the result of interaction with an external fluid in the veins after they have been formed from the intrinsic chemical heterogeneities.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Beinlich, A. et al. (2020). &amp;#8220;Instantaneous rock transformations in the deep crust driven by&lt;br&gt;reactive fluid flow&amp;#8221;. In: Nature Geoscience 13.4, pp. 307&amp;#8211;311. doi: 10.1038/s41561-&lt;br&gt;020-0554-9.&lt;/li&gt; &lt;li&gt;Pl&amp;#252;mper, O. et al. (2017). &amp;#8220;Fluid escape from subduction zones controlled by channel-&lt;br&gt;forming reactive porosity&amp;#8221;. In: Nature Geoscience 10.2, pp. 150&amp;#8211;156. doi: 10.1038/&lt;br&gt;NGEO2865.&lt;/li&gt; &lt;/ul&gt;

Analysis of Collaborative Meetings in Developing Data Mining Models

2005 ◽  
Vol 49 (5) ◽  
pp. 686-689
Author(s):  
Jiao Ma ◽  
Colin G. Drury
Keyword(s):  
Data Mining ◽  
Longitudinal Study ◽  
Microarray Data ◽  
Current Understanding ◽  
Design Approach ◽  
Field Observations ◽  
Technical Aspects ◽  
Collaborative Groups ◽  
Group Meetings

Observations of group meetings were used to help our understanding of the Data Mining (DM) process, which can take a year to complete. Over a course of three months, we followed two collaborative groups and observed their weekly meetings, where they devised DM models and explored new ways to analyze and present microarray data. The study furthered the current understanding of the DM activities by revealing its socio-technical aspects, and directed a promising design approach for a more efficient and effective DM system. Field observations of collaborative meetings disclosed that a longitudinal study is, in fact, appropriate and necessary to further understand the DM process and the system.

scholarly journals The ecology of the sponge larva

2006 ◽  
Vol 84 (2) ◽  
pp. 175-194 ◽  
Author(s):  
Manuel Maldonado
Keyword(s):  
State Of The Art ◽  
The State ◽  
Current Understanding ◽  
Field Observations ◽  
Laboratory Studies ◽  
Larval Ecology ◽  
Research Attention ◽  
Structure And Dynamics ◽  
Global Understanding ◽  
Available Information

The present work summarizes the progress attained in the study of sponge larval ecology since the state-of-the-art reviews performed in the 1970s and stresses the major weaknesses in our current understanding. Most available information on this subject comes from laboratory studies, with just occasional field observations or experiments. The data are also strongly biased because they are mostly derived from just one larval type out the eight types known in the phylum Porifera. Descriptive studies on larval histology are relatively abundant, but investigations directed at unravelling the cytological basis of the main larval behaviors are scarce. Most aspects of basic larval metabolism and sensing processes remain largely not investigated. Modelling of larval ecology is virtually lacking, with no serious attempt to investigate how the major features of larval ecology affect the structure and dynamics of sponge populations. In summary, the ecology of the sponge larva needs further research attention if we are to achieve a global understanding of the biology of the phylum Porifera.

Sign in / Sign up

Export Citation Format

Share Document