bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of sedimentology in the mobility of debris avalanches: Evidence from their deposits and granular flow experiments
Authors: Makris Symeon , Manzella Irene , Cole Paul , Roverato Matteo
Published: March 2021

Debris avalanches and lahars are among the most destructive and hazardous mass flows in volcanic environments making them important to understand from a hazard assessment perspective. Sedimentological characteristics of their deposits are important for assessing their propagation and emplacement mechanisms. Here, we compare the sedimentology of nine volcanic debris avalanches and eight lahars, by the descriptive statistics: median grain size, sand, gravel and finer particle proportion, skewness, and sorting.

Results suggest that lahars and debris avalanches diverge in their grain size distribution evolution during propagation, even when sourced from the same material. Increasing bimodality, evolution to negative skewness, with decreasing sediment size, accompanied by very poor sorting suggest comminution of particles due to particle-particle interactions in debris avalanches. Instead, preferential deposition of the coarsest particles and improved sorting suggest that the decrease in grain size of lahars is the result of debulking. The divergence is mainly caused by the high water content in lahars, which introduce different processes during propagation. This suggests, in agreement with previous studies, that debris avalanches can be considered as dense granular flows where the effect of inertial collisions of solid fragments are more important than fluid effects.

Present findings and previous sedimentological studies suggest that both volcanic and non-volcanic debris avalanches exhibit bimodal grain-size distributions, at least locally, in areas of high shear accommodation. Following these results, an experimental campaign has been carried out to test the effect of bimodality on the propagation of granular flows. These experiments are flows of bidisperse granular material on an initial inclined plane, with a horizontal accumulation surface at the bottom.  Findings confirm that the bimodality of the grain size distribution generates a more efficient shearing arrangement, which can increase the mobility of granular flows in the same way recorded in debris avalanche deposits.
Validating GIA models based on an ensemble of 3D Earth structures with present-day GPS uplift rates
Authors: Klemann Volker , Boergens Eva , Bagge Meike
Published: March 2021

Glacial-isostatic adjustment (GIA) models simulate the viscoelastic response of the solid earth due to loading. During the last glacial maximum, large areas in the northern and southern hemisphere were covered by km-thick ice sheets. Although most of the ice has been melted already 8,000 year ago, the time-delayed response of the viscoelastic earth is still a significant contribution to present-day uplift rates. The implementation of GIA models in global climate models is an essential part of the current research. Hereby, the choice of an appropriate earth structure in the GIA model plays an important role and has to be constrained by observational data.

Here, we apply present-day uplift data to constrain a set of GIA models that differ in 3D earth structure. To this end, these different GIA models are validated against GPS uplift rates provided by Schumacher et al. (2019). The GPS stations are globally distributed and not necessarily clustered in regions with strong GIA signal. For validation, regions with the largest gradient present in the GIA signal are most crucial. Thus, we use a weighting scheme, where those GPS stations get a higher weight that are less correlated to all other stations. Additionally, uncertainties in the GPS rates appear due to the length of the GPS time series and due to station specifics such as the used GPS receiver, and are provided together with the rates as standard deviations. Thence, the weighting used for the validation is the sum of the correlation derived weights and the uncertainty derived weights.

With this weighting in place, different GIA models can be validated against present day uplift rates by means of root mean square errors or mean absolute error.
Density structure of the lithospheric mantle: upscaling from minerals to peridotites
Authors: Faccincani Luca , Faccini Barbara , Casetta Federico , Mazzucchelli Maurizio , Nestola Fabrizio , Coltorti Massimo
Published: March 2021

The knowledge of the density structure of the lithospheric mantle is critical to our comprehension of tectonic and magmatic events occurring within the lithosphere and crucial to model the evolution of complex geodynamic processes (e.g., subduction dynamics, mantle plume upwelling etc). Furthermore, a thorough understanding of the density evolution at mantle conditions is essential to interpret geophysical data such as seismic tomography (e.g., Afonso et al., 2008; Stixrude and Lithgow-Bertelloni, 2012).

The density of mantle peridotites is related to chemical composition, modal abundance and elastic properties of their constituent minerals, which in turn are controlled by pressure, temperature and bulk composition of the system. Accordingly, the elastic properties of mantle minerals combined with the thermal state of the lithosphere can predict how the physical properties (e.g., density, elastic moduli) of mantle peridotites vary with depth. To this aim, (i) we examined the existing literature data (compressibility, thermal expansion and elasticity) suitable to constrain the elastic properties of peridotite minerals and (ii) we addressed the density structure of two potential lithospheric mantle sections (fertile and depleted) across different thermal regimes from the perspective of the Equations of State (EoS) of their constituent minerals.

In a mantle characterized by a relatively cold geotherm (45 mWm-2), the density of a depleted peridotitic system remains nearly constant up to about 4 GPa, while it moderately increases in a fertile system. In a mantle characterized by a relatively hot geotherm (60 mWm-2), the density of both depleted and fertile systems decreases up to about 3 GPa, due to the more rapid raise of temperature compared to pressure, and then it increases downwards.

These preliminary results show that the thermal state of the lithosphere produces a first-order signature in its density structure, with few differences owing to different modes and crystal chemical compositions.

References

Afonso, J.C., Fernàndez, M., Ranalli, G., Griffin, W.L., Connolly, J.A.D., 2008. Integrated geophysical-petrological modeling of the lithosphere and sublithospheric upper mantle: Methodology and applications. Geochemistry, Geophys. Geosystems 9, Q05008.

Stixrude, L., Lithgow-Bertelloni, C., 2012. Geophysics of Chemical Heterogeneity in the Mantle. Annu. Rev. Earth Planet. Sci. 40, 569–595.
An integrated Bayesian stratigraphic correlation approach for the Cambrian Explosion
Authors: Sinnesael Matthias , Millard Andrew R. , Smith Martin R.
Published: March 2021

The Cambrian Explosion is characterised by a large diversification of life. The precise nature of this major evolutionary event is heavily debated, featuring anomalously fast versus more gradual evolutionary scenarios. Our ability to distinguish between such scenarios hinges on the quality of global correlations and corresponding timescales. With Cambrian temporal uncertainties often in the order of millions of years, establishing such correlations and timelines is a challenging task. Here, we present a novel approach to this problem based on a probabilistic Bayesian conceptual framework. Major advantages of the Bayesian approach include the consideration of multiple information sources in a single analysis and explicit uncertainty formulations.

In the absence of good index fossils, early Cambrian correlations rely heavily on carbon isotope chemostratigraphy and ‘expert-based’ correlations. Inspired by approaches in the radiocarbon community, we have been exploring representations of stable carbon isotope variations using random walk and spline fitting models. Implementation is undertaken using Markov-chain Monte-Carlo (MCMC) approaches. Temporal calibration is mainly dependent on published state-of-the-art U-Pb zircon dating. Our model also allows for the use of different sedimentary facies. Simultaneous analysis of several sections and multiple stratigraphic variables will allow each section to inform the correlation of every other, leading to a single, objectively derived and quantitative reference curve. Ultimately, the aim is to have a coupled Bayesian model setup of both stratigraphy and morphological evolution of the fossil record. These models will better inform us on the origins of diverse animal-dominated ecosystems and their impact on Earth processes.
An assessment of marine biogeochemical processes in the tropical Atlantic in NorESMs
Authors: Koseki Shunya , Rodriguez Crespo Lander , Keenlyside Noel
Published: March 2021

Most state-of-the-art earth system model still exhibit large biases in the tropical Atlantic. This study aims to investigate how the physical bias influences the marine biogeochemical processes in the tropical Atlantic using Norwegian Earth System Model (NorESM). We assess four different configurations of NorESM: NorESM version 1is taken as benchmark (NorESM-CTL), a version of this model with a physical bias correction using anomaly coupling (NorESM-AC), and NorESM version 2 with low and medium atmospheric resolution (NorESM-LM/NorESM-MM) is also utilized.

 

With respect to NorESM-CTL, the annual-mean sea surface temperature (SST) bias is improved largely in NorESM-AC and NorESM-MM in the equatorial Atlantic and southeast Atlantic. On the other hand, the improvement of seasonal cycle of SST can be seen in NorESM-AC and the two versions of NorESM2; development of Atlantic Cold Tongue (ACT) is realistic in terms of location and timing. Corresponding to the ACT seasonal cycle, the primary production in the equatorial Atlantic is also improved and in particular, the Atlantic summer bloom is well represented in NorESM-AC and NorESM-MM even though the amount of production is still much smaller than satellite observations. This realistic summer bloom can be related to the well-represented shallow thermocline and associated nitrate supply from the subsurface ocean at the equator.
Self-consistent grain size evolution controls lithospheric shear zone formation during continental rifting
Authors: Ruh Jonas B. , Tokle Leif , Behr Whitney M.
Published: March 2021

In geodynamic numerical models, grain-size-independent dislocation creep often solely defines the governing crystal-plastic flow law in the upper mantle. However, grain-size-dependent diffusion creep may become the dominant deformation mechanism if grain size is sufficiently small. Previous studies implying composite diffusion-dislocation creep rheologies and fixed grain size suggest that the upper mantle is stratified with the dominant mechanism being dislocation creep at shallow depths and diffusion creep further down. Studies with variable grain size in the upper mantle depending on common grain-size evolution models demonstrate that the contrary might be the case, where diffusion creep is acting within the mantle lithosphere and dislocation creep in the asthenosphere below. Diffusion creep as a dominant mechanism has important implications for the overall strength of the lithosphere and therefore for the dynamic evolution of lithospheric-scale extension and orogeny.

To investigate the importance of grain size and the effects of resulting crystal-plastic creep within the upper mantle, we developed a two-dimensional thermo-mechanical numerical code based on the finite difference method with a fully staggered Eularian grid and freely advecting Lagrangian markers. The model implies a composite diffusion-dislocation creep rheology and a dynamic grain-size evolution model based on the paleowattmeter including recently published olivine grain growth laws.

Results of upper mantle extension indicate olivine grain sizes of ~7 cm for large parts of the upper mantle below the LAB, while in the lithosphere grain size ranges from ~1 mm at the Moho to ~5 cm at the LAB. This grain size distribution indicates that dislocation creep dominates deformation in the entire upper mantle. However, diffusion creep activates along lithospheric-scale shear zones during rifting where intense grain size reduction occurs to local stress increase. We furthermore test the implications of wet and dry olivine rheology and respective crystal growth laws and interpret their effects on large-scale tectonic processes. Our results help explain strain localization during extension by strength loss related to grain size reduction and consequent diffusion creep activation.
Contemporaneously growing speleothems and their value to decipher in-cave processes
Authors: Skiba Vanessa , Fohlmeister Jens
Published: March 2021

Speleothems have been developed to be valuable climate archives. Albeit much progress has been made to understand speleothem proxies, it remains difficult to differentiate between a direct climate signal and variations, which occurred due to in-cave processes like prior calcite precipitation, CO2 degassing or C exchange between dissolved inorganic C-species and cave air CO2. Here, we analyse palaeoclimate proxies of contemporaneously growing speleothems, which were extracted from the SISALv2 database (Comas-Bru et al., 2020). We argue that differences in their stable O and C isotopic composition as well as in their growth rate can only arise by differences of drip site specific conditions as climate conditions for pairs of contemporaneously growing speleothems are similar. To better understand differences in the isotopic composition and growth rate of contemporaneously growing speleothems, we investigate the in-cave processes by applying a speleothem isotope and growth model. The model is based on a Rayleigh process, which includes CO2 degassing and CaCO3 precipitation, HCO3- <—> H2O buffering as well as CO2 exchange and is able to calculate growth rates. The model accounts for CaCO3 deposition as prior calcite precipitation as well as CaCO3 deposition at the speleothem. We find that C-exchange processes are necessary to explain the linked isotopic and growth rate differences in speleothems.

 

References

Comas-Bru, L., Atsawawaranunt, K., Harrison, S., SISAL working group members (2020): SISAL (Speleothem Isotopes Synthesis and AnaLysis Working Group) database version 2.0. University Of Reading.
Highly oxygenated organic molecules (HOM) formation in the isoprene oxidation by NO3 radical
Authors: Zhao Defeng , Pullinen Iida , Fuchs Hendrik , Schrade Stephanie , Wu Rongrong , Acir Ismail-Hakki , Tillmann Ralf , Rohrer Franz , Wildt Jürgen , Guo Yindong , Kiendler-Scharr Astrid , Wahner Andreas , Kang Sungah , Luc Vereecken Luc , Mentel Thomas
Published: March 2021

       Highly oxygenated organic molecules (HOM) are found to play an important role in the formation and growth of secondary organic aerosol (SOA). SOA is an important type of aerosol with significant impact on air quality and climate. Compared to the oxidation of volatile organic compounds by O3 and OH, HOM formation in the oxidation by NO3 radical, an important oxidant at night-time and dawn, has received less attention. In this study, HOM formation in the reaction of isoprene with NO3 was investigated in the SAPHIR chamber (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). A large number of HOM including monomers (C5), dimers (C10), and trimers (C15), both closed-shell compounds and open-shell peroxy radicals, were detected. HOM were classified into various series according to their formula, which included monomers containing one or more N atoms, dimers containing 1-4 N atoms, and trimers containing 3-5 N atoms. Tentative formation pathways of HOM were proposed reflecting known NO3 and RO2 chemistry in the literature under consideration of the autoxidation via peroxy pathways and peroxy-alkoxy pathways. Further mechanistic constraints were given by the time profiles of HOM after sequential isoprene addition which enabled to differentiate first- and second-generation products. Total HOM molar yield was estimated, which suggests that HOM may contribute a significant fraction to SOA yield in the reaction of isoprene with NO3.
Searching for life in volcanic carbonate systems and the effect of temperature on organic molecules
Authors: O'Donnell Alexander
Published: March 2021

Carotenoid compounds such as β-carotene are some of the most prevalent organic molecules on Earth and are key biomarkers as there is no known abiogenic source. During diagenesis and thermal alteration, carbon undergoes well-documented changes in Raman spectra.

There has been little research into the transitional degradation of carotenoid spectra to where they are fully replaced by the carbon spectra as the main identifier of thermal maturity under Raman spectroscopy. This is an overlooked regime when discussing the search for life, terrestrial and extra-terrestrial, where current research (using Raman spectroscopy) either focuses on finding living organisms displaying common organic molecules, or looks for the elemental carbon evidence of extinct fossil life. The real world is not usually so polarised, so covering the transition between these modes of life detection will improve any detection analysis.

For this study the volcanic thermal spring system in Viterbo, Italy was used as a field-based laboratory. The high rate of carbonate precipitation in these thermal springs, the wide range of thermal regimes (58°C to 25°C), and the prevalence of fast-growing algae in the run-off streams, give excellent preservation of a range of organic matter states at directly measurable temperatures.

The results demonstrate how the Raman spectra of the carotenoid compounds change with hydration, death of the organism, and thermal alteration of the organic material. The relationship between the spectra of the carotenoid compound and the elemental carbon spectra in the transition zone is also shown.

This study expands on the use of Raman spectroscopy of carbon as a low-temperature geothermometer, and provides a framework for the spectral response of organic matter in an often-overlooked geological regime. It is anticipated that the fields of geothermal energy, climatology, geobiology and astrogeobiology, could all benefit from this study, incorporating this enhanced thermal alteration data into existing and future work.
Extreme wind projections over Europe in the high-resolution Euro-CORDEX ensemble
Authors: Sobolowski Stefan , Outten Stephen
Published: March 2021

 

Extreme weather events represent one of the most visible and immediate hazards to society. Many of these types of phenomena are projected to increase in intensity, duration or frequency as the climate warms. Of these extreme winds are among the most damaging historically over Europe yet assessments of their future changes remain fraught with uncertainty. This uncertainty arises due to both the rare nature of extreme wind events and the fact that most model are unable to faithfully represent them. Here we take advantage of a 15-member ensemble of high-resolution Euro-CORDEX simulations (~12km) and investigate projected changes in extreme winds using a peaks-over-threshold approach. Additionally, we show that - despite lingering model deficiencies and inadequate observational coverage - there is clear added value of the higher resolution simulations over coarser resolution counterparts. Further, the spatial heterogeneity and highly localized nature is well captured. Effects such as orographic interactions, drag due to urban areas, and even individual storm tracks over the oceans are clearly visible. As such future changes also exhibit strong spatial heterogeneity. These results emphasize the need for careful case-by-case treatment of extreme wind analysis, especially when done in a climate adaptation or decision-making context. However, for more general assessments the picture is clearer with increases in the return period (i.e., more frequent) extreme episodes projected for Northern, Central and Southern Europe throughout the 21st century. While models continue to improve in their representation of extreme winds, improved observational coverage is desperately needed to better constrain and obtain more robust assessments of future extreme winds over Europe and elsewhere. 
Social consequences of climate change in the Arctic towns
Authors: Klyuchnikova Elena , Riabova Larisa , Masloboev Vladimir
Published: March 2021

Climate change in the Arctic is noticeable and affecting the well-being of the population. The health and emotional state, food and water availability, livelihoods are on the threat. The towns are particularly sensitive to climate change. Their population and infrastructure density is exceptionally high, and temperature fluctuations, as well as extreme weather events, have an exceptionally strong impact on air and water quality, health and other components of human well-being. At the same time, urban communities in the Arctic, especially in industrial development zones, represent a little-studied area in this case.

The report presents the interdisciplinary study results concerning the climate change consequences for the population of Russian Arctic industrial developed areas. The study carried out in Murmansk Region which is a highly industrial and highly urbanized region that is completely included in the Arctic zone of the Russian Federation. Qualitative methods were used; in-depth (more than 50 questions) interviews were conducted with residents of several towns in the region. The study showed corresponds between the subjective perceptions of climate change by urban residents of the Murmansk Region with objective data on meteorological parameters changes. The surveyed urban residents feel changes in health and environmental management practices, and many respondents associate these changes with climate fluctuations. Such a phenomenon as the destruction of infrastructure (residential, public and industrial buildings, roads, energy infrastructure) due to climate change has not been identified. Concerns have been raised about the potential impact of climate warming on the ability to have a decent job due to reduced employment in some industries (such as energy).

The results obtained contribute to a better understanding of the social consequences of climate change in the Russian Arctic. This is important for adaptation actions development.

 
New advances on the magnetic chronostratigraphy of cave sediments in Atapuerca Gran Dolina, Spain
Authors: Pares Josep M , Duval Mathieu , Campaña Isidoro , Bermúdez de Castro José M. , Carbonell Eudald
Published: March 2021

Magnetostratigraphy has proven to be a powerful and versatile method as well the first line of defence for dating sediments. When properly anchored to the Geomagnetic Polarity Time Scale (GPTS), chron boundaries provide a basis for numerical dating by correlating the local magnetostratigraphy to the GPTS. A caveat and intrinsic limitation when anchoring magnetic stratigraphy to the GPTS is that we deal with essentially a binary code, a sequence of normal and reverse polarity zones. To overcome such limitation biostratigraphy or (ideally) numerical (absolute) age dating is required. Unfortunately, numerical dating of sediments is typically hampered by the lack of amenable minerals for the application of standard methods such as Ar-Ar, requiring thus the use of less conventional methods. Burial dating is possible using methods such as Electron Spin Resonance (ESR) on optically bleached quartz grains. Similar to luminescence, ESR is a paleodosimetric method that provides the time elapsed since the last exposure of quartz grains to natural sun light. Cave sediments are particularly amenable for paleodosimetric methods, as sediments are preserved in the dark and the ESR signal should survive over the geologic history of the deposits. On the down side, we date the moment when the quartz grain enters the karst system, not its deposition. If the transit time is too long, this might be an issue and we would be significantly overestimating the true burial age. Caves at Atapuerca (N Spain) hold the richest Quaternary paleontological record in Eurasia, including fossils and lithic tools. Sediments in these caves have been traditionally dated via magnetostratigraphy by identifying the Matuyama-Brunhes reversal (0.78 Ma) thus providing the Lower to Middle Pleistocene boundary. Nevertheless, the appearance of older sediments in the caves required the combination of paleomagnetism with methods such as ESR to interpret older intra-Matuyama Subchrons. In the deepest levels of the Gran Dolina cave, close to the floor of the cavity, a number of short intervals of normal polarity have been identified in the fluviatile sediments belonging to TD1 unit, which we interpret in terms of Subchrons using ESR ages of quartz grains. We will discuss both paleomagnetic data and interpret the magnetic polarity stratigraphy in the view of the ESR ages obtained from the Multiple Centre (MC) approach. 
Carbon biomass, carbon-to-chlorophyll a ratios and growth rates of phytoplankton in Jiaozhou Bay, China
Authors: Guo Shujin , Sun Xiaoxia
Published: March 2021

Carbon biomass, carbon-to-chlorophyll a ratio (C:Chl a) values and growth rates of phytoplankton cells were studied during four seasonal cruises in 2017 and 2018 in Jiaozhou Bay, China. Water samples were collected from twelve stations, and phytoplankton carbon biomass (phyto-C) was estimated from microscope-measured cell volumes. Phyto-C ranged from 5.05 to 78.52 μg C/L (mean 28.80 μg C/L) in the bay, and it constituted a mean of 38.16% of the total particulate organic carbon in the bay. High phyto-C values always appeared in the northern or northeastern bay. Diatom carbon was predominant during all four cruises. Dinoflagellate carbon contributed much less (<30%) to the total phyto-C, and high values always appeared in the outer bay. The C:Chl a of phytoplankton cells varied from 11.50 to 61.45 (mean 31.66), and high values appeared in the outer bay during all four seasons. The phyto-C was also used to calculate the intrinsic growth rates of phytoplankton cells in the bay, and phytoplankton growth rates ranged from 0.56 to 1.96 day-1; the rate was highest in summer (mean 1.79 day-1), followed by that in fall (mean 1.24 day-1) and spring (mean 1.17 day-1), and the rate was lowest in winter (mean 0.77 day-1). Temperature and silicate concentration were found to be the determining factors of phytoplankton growth rates in the bay. To our knowledge, this study is the first report on phytoplankton carbon biomass and C:Chl a based on water samples in Jiaozhou Bay, and it will provide useful information for studies on carbon-based food web calculations and carbon-based ecosystem models in the bay.
Global consistency in response of terrestrial ecosystem respiration to temperature
Authors: Zhang Huanyuan , Zhang Zhiyuan , Cui Zikun , Tao Feng , Chen Ziwei , Chang Yaxuan , Magliulo Vincenzo , Wohlfahrt Georg , Zhao Dongsheng
Published: March 2021

Many studies have been carried out to quantify the trend of terrestrial ecosystem respiration (Re) in a warming world, but a conclusive answer has not yet been confirmed because the temperature sensitivity of Re was found inconsistent under different scales or regarding different types of respiratory flux.  Aiming at clarifying the relationship between temperature and Re across different scales, we proposed a method to counteract the confounding effect and applied nine empirical models to a 1,387 site-years FLUXNET dataset.  Regarding the temperature sensitivity of half-hourly Re records, we found a surprisingly consistent result that the sigmoid functions outcompeted other statistical models in almost all datasets (account for 82%), and on average, achieved a staggering R2 value of 0.92, indicating the positive correlation between Re and temperature on fine time scale (within one site-year dataset).  Even though Re of all biomes followed sigmoid functions, the parameters of the S-curve varied strongly across sites.  This explains why measured Q10 value (an index denote temperature sensitivity) largely depends on observation season and site.  Furthermore, on the interannual variation of Re, we did not find any relationship between mean annual temperature (MAT) and mean annual Re within any site, which implies that the small year-to-year variation of the sigmoid pattern is large enough to counteract the warming effect on Re.  This study thereby put forward a conceptual model to integrate the relationship between temperature and Re under different scales. It also provided evidences to support the argument that the relationship between MAT and mean annual Re (i.e., respiration under global warming) should not be inferred from studies on other temporal or spatial scales.
Thermal history of the Siberian platform: Apatite Fission-Track data from the Permian-Triassic magmatic complexes
Authors: Bagdasaryan Tatyana , Veselovskiy Roman , Zaitsev Viktor , Latyshev Anton
Published: March 2021

The largest continental igneous province, the Siberian Traps, was formed within the Siberian platform at the Paleozoic-Mesozoic boundary, ca. 252 million years ago. Despite the continuous and extensive investigation of the duration and rate of trap magmatism on the Siberian platform, these questions are still debated. Moreover, the post-Paleozoic thermal history of the Siberian platform is almost unknown. This study aims to reconstruct the thermal history of the Siberian platform during the last 250 Myr using the low-temperature thermochronometry. We have studied intrusive complexes from different parts of the Siberian platform, such as the Kotuy dike, the Odikhincha, Magan and Essey ultrabasic alkaline massifs, the Norilsk-1 and Kontayskaya intrusions, and the Padunsky sill. We use apatite fission-track (AFT) thermochronology to assess the time since the rocks were cooled below 110℃. Obtained AFT ages (207-173 Ma) are much younger than available U-Pb and Ar/Ar ages of the traps. This pattern might be interpreted as a long cooling of the studied rocks after their emplacement ca. 250 Ma, but this looks quite unlikely because contradicts to the geological observations. Most likely, the rocks were buried under a thick volcanic-sedimentary cover and then exhumed and cooled below 110℃ ca. 207-173 Ma. Considering the increased geothermal gradient up to 50℃/km at that times, we can estimate the thickness of the removed overlying volcanic-sedimentary cover up to 207-173 Ma as about 2-3 km.

The research was carried out with the support of RFBR (grants 20-35-90066, 18-35-20058, 18-05-00590 and 18-05-70094) and the Program of development of Lomonosov Moscow State University.
From clouds to crust - Cloud diversity and surface conditions in atmospheres of rocky exoplanets
Authors: Herbort Oliver , Woitke Peter , Helling Christiane , Zerkle Aubrey
Published: March 2021

One of the fundamental questions for planetary science is how surfaces of other planets similar to the rocky bodies in our solar system look like. What is the rock structure like? Will there be water? Are there any active atmospheric cycles? How can these different conditions be detected?

The current space missions and ground based instruments allow the detection of specific gas species and some cloud compositions in atmospheres of giant exoplanets. With instruments  installed in the near future and space crafts currently being build or planned, these kind of observations will be available for planets with smaller sizes and an overall rocky composition. We aim to further understand the connection of the conditions of the upper atmosphere with the conditions on the crust of the planet (temperature, pressure, composition).

Our equilibrium chemistry models allow us to investigate the expected crust and near-crust-atmosphere composition. With this, we investigate the conditions under which liquid water is actually stable at the surface of a planet and not incorporated in hydrated rocks. Based on this crust - near-crust-atmosphere interaction we build an atmospheric model, which allows us to investigate what kind of clouds are stable and could be present in atmospheres of rocky exoplanets. This allows us to predict what clouds on other planets could be made of. Potential detection of cloud condensates and the high altitude gas phase can constrain the overall surface conditions on those planets. 
PERL: A multilevel strategy for liquefaction hazard assessment in complex stratigraphic successions
Authors: Varone Chiara , Baris Anna , Caciolli Maria Chiara , Fabozzi Stefania , Gaudiosi Iolanda , Marcini Marco , Martelli Luca , Modoni Giuseppe , Moscatelli Massimiliano , Paolella Luca , Simionato Maurizio , Spacagna Rose Line , Razzano Roberto
Published: March 2021

In May and June 2012, Emilia region (Italy) was struck by a seismic crisis characterized by more than 2000 earthquakes with two main shocks (20 May and 29 May events with ML 5.9 and 5.8, respectively) and several earthquake-induced effects. Relevant liquefaction events were observed all over the area showing a maximum intensity at San Carlo and Mirabello, two main hamlets in the Terre del Reno Municipality. In this work, a methodology is proposed for assessing liquefaction susceptibility in wide areas characterized by complex geo-stratigraphic conditions through a multi-level approach based on simplified models. To this aim, extensive geological studies and more than one thousand geophysical and geotechnical surveys available from previous studies have been collected in a dedicated geographical information system. The database is structured to guarantee data and metadata harmonization and standardization, useful for the realization of an integrated and interoperable system progressively supplemented with new information. Preliminary 2D and 3D high resolution geological and geotechnical models are elaborated to reconstruct the complex subsoil setting of Terre del Reno area.  This study forms the base for the 2D numerical modelling carried out with a finite difference code (FLAC) to identify the mechanism of pore pressure increase and of liquefaction triggering. The rationale behind this study concerns the definition of a simplified approach based on synthetic indicators. Specifically, starting from parametric analyses, the role of different variables on the triggering process is evaluated together with the definition of set of thresholds able to model the occurrence of liquefaction effects. The spatial variability of the soil properties, layering and mechanical characteristics is considered with a geo-statistical approach. A comparison between the liquefaction effects observed in 2012 and the results obtained from calculations is performed for demonstrating the reliability of the proposed approach in extensively simulating a liquefaction occurrence.
Changes in land use in the last two centuries in the Po lowlands (northern Italy)
Authors: Meli Matteo , Bruno Luigi
Published: March 2021

Changes in land use represent, after fossil-fuel combustion, the greatest cause of greenhouse-gases emission into the atmosphere. Coastal wetlands, also referred as coastal blue carbon ecosystems (e.g. salt marshes, mangrove forests, seagrass meadows, swamps), represent one of the most powerful C sinks among the Earth’s ecosystems, being capable to sequester organic carbon (OC) at rates ca. 30-50 times higher than terrestrial forests. Historically, land reclamation for agriculture, farming and urban expansion, severely impacted coastal wetlands, causing their loss and degradation. Wetlands drainage lead to the oxidation of organic matter previously stored under anaerobic conditions and the release of CO2 into the atmosphere. Only recently the critical role of blue carbon ecosystems in climate-change mitigation has been recognised, highlighting the importance of protecting and studying these precious environments.

In this work, changes in land use in the last two centuries are reconstructed through comparison with historical maps. At the beginning of the 19th century Napoleon Bonaparte requested the development of high-quality maps of occupied territories. Among these, the so-called ‘Carta del Ferrarese’ (CdF), completed between 1812 and 1814, is composed of 38 sheets and represents, to a scale of 1:15.000, 240.000 hectares of the Po lowlands, roughly corresponding to the present-day Ferrara district. The CdF, archived at the Kriegsarchiv in Vienna, is an extraordinary example among historical maps for its high quality and accuracy, which constitute a two-centuries-old reliable paleo-landscape picture.

Within the Historical Land Use Change research project, leaded by the Emilia-Romagna Statistical and GIS Service, the CdF was scanned, accurately georeferenced and orthorectified, showing a surprising generalized match with recent maps. More than 31.000 polygons were digitized in a GIS environment and interpreted on the basis of the European Corine Land Cover codes, properly modified for the land uses at the time.

Comparison with the recent land use analysis, carried out in 2014, highlights changes in land use, mainly related to land reclamation. Salt marshes and swamps, originally extended for 100.000 hectares, were reduced of about 85%, starting from 1861. Major phases of land reclamation occurred in 1870s and 1960s. Geochemical analyses on shallow samples (depth < 50 cm), depict OC content of artificially drained soils < 5% of the total volume. Soil texture testifies to the almost complete mineralization of OC after reclamation. Only recently drained soils show higher OC content, in the range of 10-15%.
Biases in the Tropical Atlantic in Seasonal Forecast System GloSea5
Authors: Collier Tamara , Kettleborough Jamie , Scaife Adam , Hermanson Leon , Davis Philip
Published: March 2021

It is well known that climate models commonly show biases in the Tropical Atlantic including reduced cold tongue development in the boreal summer. This work investigates whether these biases are present in the Met Office Seasonal Forecast System (GloSea5) at seasonal lead times and the impact they have on teleconnections to the North Atlantic, a key area for forecasting for Northern Europe.

GloSea5 hindcasts covering the period 1993 – 2016 are analysed for winter and summer start dates and biases are calculated with comparison to ERA Interim for sea surface temperature, near surface winds and upper tropospheric winds, and the Global Precipitation Climatology Project (GPCP) for Rainfall Rate. In contrast to fully developed climate model biases, enhanced cold tongue development is found in the summer months, and a general cold bias occurs in the SST in both winter and summer. This shows that biases in initialised forecasts do not simply asymptote to the climate model error but show more complex behaviour including a change in the sign of the bias. Easterly winds are found to be strengthened throughout and signs of a double Inter Tropical Convergence Zone (ITCZ) are observed in the winter season. The ITCZ in both seasons is shown to be a narrower band of heavier rain in GloSea5 compared to the GPCP.  We investigate how these tropical biases propagate into the North Atlantic and change the forecast biases there.
Physical experiment investigation on progressive deformation of shear slip surface of the soil slope
Authors: Xie Qiang , Ban Yuxin , Wu Zhihui , Fu Xiang
Published: March 2021

The sliding surface deformation of the soil slope mainly presents progressive failure characteristics, and serial acoustic emission (AE) signals are generated during the deformation process of progressive landslide. A model test aiming at reproducing the typical shear surface deformation of a soil slope is designed. The displacement, AE data and corresponding time-frequency characteristics are comprehensively analyzed to evaluate the progressive deformation behavior. Comparisons with different granular backfills measurements show that cumulative AE count increase proportionally with the shear surface displacement, and the experiments demonstrate that the glass sand backfill exhibits remarkable AE detection characteristics and stronger correlation results. Significantly, AE signal exhibits variational dominant frequencies at different deformation stages, and there is the significant phenomenon that not only the low frequency signals generated with a significantly increase number, at the same time the continuous high frequency signals appear during the accelerating deformation stage. Furthermore, from the statistical trend of the energy percentage of the high frequency band into 312.5~500 kHz, it’s found that the correlative energy proportion occupies up to 15%, or even higher during the accelerating stage, indicating that the landslide may be about to enter a severely dangerous stage. The experiments show that the frequency characteristic of the AE signal can be effectively used as the early warning index, which may be the promising reference of the field warning monitoring for the soil progressive landslides.
Flow and fracturing conditions before the segmentation of experimental dikes 
Authors: Chavez Jazmin , Cerca Mariano
Published: March 2021

The uprise of  magma dikes that split in branches  are regularly outcropping as en echelon structures, segmented dikes, or finger like intrusions are documented examples. Dike segmentation and finger formation at different scales have been attributed commonly to effects of the host rock: 1) crustal heterogeneities that interact with the magma such as faults, fractures, and joints; 2) local rotation of the principal stress axes orientations during emplacement;  3) changes in the host rock elastic properties due to chemical corrosion, unconsolidation and weathering. Less attention has been devoted to the effect of the magma flow in leading to segmentation and formation of fingers, but the effect of fluid flow might be relevant due to the complex flow dynamics of magmas.  In past experiments presented by  Chavez-Alvarez et al.  (2020a) and Chavez-Alvarez and Cerca (2020b), he relevance of viscous forces in hydrofracturing was analyzed by quantitatively comparing the evolution of experimental dikes of contrasting rheology (Newtonian and shear thinning), where segmentation was documented for the case of shear thinning fluids. Here we provide an analysis of the hydrofracturing conditions that prevail before the segmentation of hydrofractures that transport shear thinning fluids. We evaluated parameters of toughness and viscous regimes in conditions of the hydrocrack inception, early development and propagation before segmentation. Furthermore some aspects of the flow such as Reynolds number and flow trajectories inside the experimental dikes are presented. 

References

Chàvez-Alvarez, M. J., Cerca-Martìnez, M. Bustos-Cervantes N. 2020a. Contrasting emplacement modes of water (Newtonian) and Carbopol suspension (shear thinning) injected in gelatin: insights for magma dikes.   (In revision).

Chàvez-Alvarez, M. J. and Cerca-Martìnez, M. 2020b: Dyke segmentation: an experimental approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13768, https://doi.org/10.5194/egusphere-egu2020-13768, 2020

 
Strain-partitioning and mechanics of deformation during oblique indentation: Inferences from the SE external Dinarides post- middle Miocene evolution
Authors: Feliu Nil , Demir Vedad , Matenco Liviu , Mrdak Milica , Radusinović Slobodan , Đaković Martin
Published: March 2021

Late-stage orogenic evolution often leads to multiple segmented slab systems, where the relative motion along oblique plate boundaries partitions the crustal strain into strike-slip and reverse faulting. The strain partitioning patterns and mechanics of deformation are thought to be closely related to the rheology inherited from previous tectonic events that affected various orogenic areas. The SE External Dinarides is one place to study such strain partitioning in a less understood tectonic setting. The Dinarides orogenic build-up is characterised by top SW thrusting during Late Cretaceous to Oligocene times. Subsequently, the N to NE indentation of the Adria microplate took place in this area after an early - middle Miocene period of generalized extension and was characterised by N-S to NNE-SSW oriented contraction, which is oblique to the inherited NW-SE oriented structural grain. We have studied the interplay between various structures creating strain partitioning during the Adria indentation in a SE External Dinarides region situated between the Trebinje city in SE Bosnia and Herzegovina and the Tivat city of SW Montenegro.

The post- middle Miocene orogenic evolution is characterised by regional NNW-SSE to N-S dextral strike-slip faulting associated with strain partitioning by the reactivation of NW-SE inherited rheological weak zones (former thrusts, nappe contacts or rheologically weak sediments). Kinematic analyses along individual structures define the strain partitioning pattern by a number of fault groups. The kinematically constrained mechanics of deformation (correlated to strain partition groups) in focus areas depict a gradual SE-ward transfer of deformation in the external thrust sheets of Montenegro. Such migration of deformation is done by an interplay between strike-slip, high-angle reverse faults and thrusts, which are locally associated with moderate block rotations (CW and CCW). The overall analysis demonstrates that oblique motions in advanced orogenic stages do not constrain a single paleostress field, and therefore they should be analysed by an improved kinematic approach aimed to understand strain partitioning and their effects superposed over an inherited structural grain.
A conflict between traditional flood measures and maintaining river ecosystems. A case study in river Lærdal, Norway
Authors: Juárez Ana , Alfredsen Knut , Stickler Morten , Adeva-Bustos Ana , Seguín-Garcia Sonia , Hansen Bendik , Suarez Rodrigo
Published: March 2021

Floods are among the most damaging natural disasters which are likely to increase with the effects of climate change and changes in land use. Therefore, rivers have been the focus of engineering for establishing structural flood mitigation measures. Traditional flood infrastructure, such as levees and dredging have threatened floodplains and river ecosystems and during the last decade, sustainable reconciliation of freshwater ecosystems is increasing. However, we still find many areas where these traditional measures are proposed and it is challenging to find tools for evaluations of different measures and quantification of the possible impacts. We propose the use of hydraulic modelling and remote sensing data for evaluation of different flood strategies and quantification of changes in hydraulic parameters in an ecological scale. This is applied in Lærdal River, in Norway, a national salmon river specially recognized by its environment for Atlantic salmon, where the Norwegian Water Resources and Energy Directorate (NVE) has proposed l flood measures that include confinement with walls and dredging in the riverbed. Results show that the constructing a higher wall could avoid dredging in the river bed resulting in a most cost-effective solution. Dredging could improve hydraulic conditions for juvenile salmon if applied as river restoration measure but channelization of the river would have big impacts in the river ecosystem.