- Geosciences, Vol. 10, Pages 128: Implementation and Use of a Mechanical Cone Penetration Test Database for Liquefaction Hazard Assessment of the Coastal Area of the Tuscany Region
This paper describes the implementation and use of a mechanical cone penetration test (CPTm) database for the evaluation of the liquefaction potential in some areas of Tuscany. More specifically, the database contains 4500 CPTm covering an area of 1787 square km and mainly concerns some coastal areas of Tuscany. Available simplified liquefaction evaluation procedures (LEPs) are mainly based on piezocone CPT (CPTu) test results and not on CPTm. An early interest on developing LEPs with reference to CPTm became quite soon obsolete because of the widespread use of piezocone. Unfortunately, in Italy, the use of CPTm is very popular. After the 2012 seismic sequence of Emilia-Romagna, the use of CPTm for liquefaction risk analysis has seen a renewed interest, even though such a topic should require further studies. This paper shows an empirical approach for liquefaction triggering assessment by CPTm using existing LEPs, thus making possible the use of the developed CPTm database for the preliminary screening of the study area.
- Geosciences, Vol. 10, Pages 129: Simultaneous Magmatic and Hydrothermal Regimes in Alta–Little Cottonwood Stocks, Utah, USA, Recorded Using Multiphase U-Pb Petrochronology
Magmatic and hydrothermal systems are intimately linked, significantly overlapping through time but persisting in different parts of a system. New preliminary U-Pb and trace element petrochronology from zircon and titanite demonstrate the protracted and episodic record of magmatic and hydrothermal processes in the Alta stock–Little Cottonwood stock plutonic and volcanic system. This system spans the upper ~11.5 km of the crust and includes a large composite pluton (e.g., Little Cottonwood stock), dike-like conduit (e.g., Alta stock), and surficial volcanic edifices (East Traverse and Park City volcanic units). A temperature–time path for the system was constructed using U-Pb and tetravalent cation thermometry to establish a record of >10 Myr of pluton emplacement, magma transport, volcanic eruption, and coeval hydrothermal circulation. Zircons from the Alta and Little Cottonwood stocks recorded a single population of apparent temperatures of ~625 ± 35 °C, while titanite apparent temperatures formed two distinct populations interpreted as magmatic (~725 ± 50 °C) and hydrothermal (~575 ± 50 °C). The spatial and temporal variations required episodic magma input, which overlapped in time with hydrothermal fluid flow in the structurally higher portions of the system. The hydrothermal system was itself episodic and migrated within the margin of the Alta stock and its aureole through time, and eventually focused at the contact of the Alta stock. First-order estimates of magma flux in this system suggest that the volcanic flux was 2–5× higher than the intrusive magma accumulation rate throughout its lifespan, consistent with intrusive volcanic systems around the world.
- Geosciences, Vol. 10, Pages 127: Regional Flood Frequency Analysis Using An Artificial Neural Network Model
This paper presents the results from a study on the application of an artificial neural network (ANN) model for regional flood frequency analysis (RFFA). The study was conducted using stream flow data from 88 gauging stations across New South Wales (NSW) in Australia. Five different models consisting of three to eight predictor variables (i.e., annual rainfall, drainage area, fraction forested area, potential evapotranspiration, rainfall intensity, river slope, shape factor and stream density) were tested. The results show that an ANN model with a higher number of predictor variables does not always improve the performance of RFFA models. For example, the model with three predictor variables performs considerably better than the models using a higher number of predictor variables, except for the one which contains all the eight predictor variables. The model with three predictor variables exhibits smaller median relative error values for 2- and 20-year return periods compared to the model containing eight predictor variables. However, for 5-, 10-, 50- and 100-year return periods, the model with eight predictor variables shows smaller median relative error values. The proposed ANN modelling framework can be adapted to other regions in Australia and abroad.
- Geosciences, Vol. 10, Pages 126: The Avalanche of Les Fonts d’Arinsal (Andorra): An Example of a Pure Powder, Dry Snow Avalanche
On 8th February 1996, in the north-western part of Andorra in the Pyrenees, the Les Fonts d’Arinsal (LFd’A) pure powder avalanche was triggered, descending some 1200 m to the bottom of the Arinsal valley and continuing up the opposite slope for about 200 m. This size 4–5 avalanche reached velocities of up to 80 ms−1, devastated 18 ha of forest, involved a minimum volume of up to 1.8 × 106 m−3 and caused major damage to eight buildings. Fortunately, no one was injured thanks to an evacuation, but 322 people lost their properties. This study describes the physical characteristics of the LFd’A avalanche path and provides data on earlier avalanches, the meteorological synoptic situation and snowpack conditions that generated the avalanche episode, the warning and preventive actions carried out, the effects and evidence of the large avalanche, and the defence system implemented afterwards. A discussion of the avalanche dynamics based on observations and damage, including the role of snow entrainment, the total lack of characteristic dense flow deposits, as well as the evidence of a two-phase flow (fluidisation and suspension), is presented. This case study is an example of a paradigmatic large, pure powder, dry-snow avalanche, which will be useful for model calibration.
- Geosciences, Vol. 10, Pages 125: Lava Flow Roughness on the 2014–2015 Lava Flow-Field at Holuhraun, Iceland, Derived from Airborne LiDAR and Photogrammetry
Roughness can be used to characterize the morphologies of a lava flow. It can be used to identify lava flow features, provide insight into eruption conditions, and link roughness pattern across a lava flow to emplacement conditions. In this study, we use both the topographic position index (TPI) and the one-dimensional Hurst exponent (H) to derive lava flow unit roughness on the 2014–2015 lava field at Holuhraun using both airborne LiDAR and photogrammetric datasets. The roughness assessment was acquired from four lava flow features: (1) spiny lava, (2) lava pond, (3) blocky surface, and (4) inflated channel. The TPI patterns on spiny lava and inflated channels show that the intermediate TPI values correspond to a small surficial slope indicating a flat and smooth surface. Lava pond is characterized by low to high TPI values and forms a wave-like pattern. Meanwhile, irregular transitions patterns from low to high TPI values indicate a rough surface that is found in blocky surface and flow margins. The surface roughness of these lava features falls within the H range of 0.30 ± 0.05 to 0.76 ± 0.04. The roughest surface is the blocky, and inflated lava flows appear to be the smoothest surface among these four lava units. In general, the Hurst exponent values in the 2014–2015 lava field at Holuhraun has a strong tendency in 0.5, both TPI and Hurst exponent successfully derive quantitative flow roughness.
- Acute glyphosate exposure does not condition the response of microbial communities to a dry–rewetting disturbance in a soil with longhistory of glyphosate–based herbicides
Acute glyphosate exposure does not condition the response of microbial communities to a dry–rewetting disturbance in a soil with longhistory of glyphosate–based herbicides Marco Allegrini, Elena del Valle Gomez, and María Celina Zabaloy SOIL Discuss., https//doi.org/10.5194/soil-2020-11,2020 Preprint under review for SOIL (discussion: open, 0 comments) A research was conducted to assess the response of microbial communities in a soil with long history of glyphosate-based herbicides to a secondary imposed perturbation (dry-rewetting event). Both perturbations could increase their frequency under current agricultural practices and climate change. The results of this study demonstrates that acute exposure to a glyphosate-based herbicide does not have a conditioning effect on the response of microbial communities to the dry-rewetting event.
- Game theory interpretation of digital soil mapping convolutional neural networks
Game theory interpretation of digital soil mapping convolutional neural networks José Padarian, Alex B. McBratney, and Budiman Minasny SOIL Discuss., https//doi.org/10.5194/soil-2020-17,2020 Preprint under review for SOIL (discussion: open, 0 comments) In this paper we introduce the use of game theory to interpret a digital soil mapping (DSM) model to understand the contribution of environmental factors to the prediction of soil organic carbon (SOC) of Chile. The analysis corroborated that the SOC model is capturing sensible relationships between SOC and climatic and topographical factors. We were able to represent them spatially (map) addressing the limitations of the current interpretation of models in DSM.
- Obtaining more benefits from crop residues as soil amendments by application as chemically heterogeneous mixtures
Obtaining more benefits from crop residues as soil amendments by application as chemically heterogeneous mixtures Marijke Struijk, Andrew P. Whitmore, Simon R. Mortimer, and Tom Sizmur SOIL Discuss., https//doi.org/10.5194/soil-2020-9,2020 Preprint under review for SOIL (discussion: open, 0 comments) Crop residues are widely available on-farm resources containing carbon and nutrients, but as soil amendments, their decomposition does not always benefit the soil. We applied mixtures of crop residues that are chemically different from each other and found significantly increased soil organic matter and available nitrogen levels. Applying crop-residue mixtures has practical implications involving the removal, mixing and re-application, rather than simply returning crop residues to soils in-situ.
- Depletion of soil carbon and aggregation after strong warming of a subarctic Andosol under forest and grassland cover
Depletion of soil carbon and aggregation after strong warming of a subarctic Andosol under forest and grassland cover Christopher Poeplau, Páll Sigurðsson, and Bjarni D. Sigurdsson SOIL, 6, 115–129, https://doi.org/10.5194/soil-6-115-2020, 2020 Global warming leads to increased mineralisation of soil organic matter, inducing a positive climate–carbon cycle feedback loop. Loss of organic matter can be associated with loss of soil structure. Here we use a strong geothermal gradient to investigate soil warming effects on soil organic matter and structural parameters in subarctic forest and grassland soils. Strong depletion of organic matter caused a collapse of aggregates, highlighting the potential impact of warming on soil function.
- Time-lapse monitoring of root water uptake using electrical resistivity tomography and mise-à-la-masse: a vineyard infiltration experiment
Time-lapse monitoring of root water uptake using electrical resistivity tomography and mise-à-la-masse: a vineyard infiltration experiment Benjamin Mary, Luca Peruzzo, Jacopo Boaga, Nicola Cenni, Myriam Schmutz, Yuxin Wu, Susan S. Hubbard, and Giorgio Cassiani SOIL, 6, 95–114, https://doi.org/10.5194/soil-6-95-2020, 2020 The use of non-invasive geophysical imaging of root system processes is of increasing interest to study soil–plant interactions. The experiment focused on the behaviour of grapevine plants during a controlled infiltration experiment. The combination of the mise-à-la-masse (MALM) method, a variation of the classical electrical tomography map (ERT), for which the current is transmitted directly into the stem, holds the promise of being able to image root distribution.