Bathymetry and Shallow Seismic Imaging of the 2018 Flank Collapse of Anak Krakatau

The flank failure and collapse of Anak Krakatau on December 22nd, 2018 triggered a destructive tsunami. Whether the prior activity of the volcano led to this collapse, or it was triggered by another means, remains a challenge to understand. This study seeks to investigate the recent volcano submarine mass-landslide deposit and emplacement processes, including the seafloor morphology of the flank collapse and the landslide deposit extent. Bathymetry and sparker seismic data were used during this study. Bathymetry data collected in August, 2019 shows the run-out area and the seafloor landslide deposit morphology. Bathymetry data acquired in May, 2017, is used as the base limit of the collapse to estimate the volume of the flank collapse. Comparisons between seismic data acquired in 2017 and 2019 provide an insight into the landslide emplacement processes, the deposit sequence, and structure below the seafloor. From these results we highlight two areas of the submarine-mass landslide deposit, one proximal to Anak Krakatau island (∼1.6 km) and one distal (∼1.4 km). The resulting analysis suggests that the submarine-mass landslide deposit might be produced by a frontally compressional, faulted, landslide, triggered by the critical stability slope, and due to the recent volcanic activity. Blocky seabed features clearly lie to the southwest of Anak Krakatau, and may represent the collapse blocks of the landslide. The seismic analysis of the data acquired in August, 2019 reveals that the blocky facies extends to ∼1.62 km in the width around Anak Krakatau, and the block thicknesses vary up to 70.4 m. The marine data provides a new insight into the landslide run out and extent, together with the landslide deposit morphology and structure that are not available from satellite imagery or subaerial surveys. We conclude that the landslide run out area southwest of the recent collapse, is ∼7.02 ± 0.21 km2.

An Analysis of Factors Affecting Flowslide Deposit Morphology Using Taguchi Method

Flowslides, as one type of landslides, are becoming a research hotspot due to their high speed and long runout distance, which can cause tremendous damage and economic loss. The scale of damage and deposit morphology of flowslide is closely related to factors like deposit volume, slope height, and slope angle. In order to assess the influence of these factors, a sandbox apparatus is developed, and the Taguchi method is used to design an experimental scheme to analyze the results of factors affecting the deposit morphology of flowslide. The results show that the factor that has the greatest impact on flowslide deposit morphology is slope angle, followed by the influence of volume and slope height. As slope angle increases, the maximum width, maximum length, area, and length-width ratio of the deposit first increase and then decrease. In addition, there should be a critical angle in the changes of deposit morphology that is between 60° and 70° under the experimental conditions. When the volume is 5.4 × 10−3 m3, the slope angle is 70°, the slope height is 0.90 m, and the changes of deposit morphology of the flowslide are the largest. In this study, considering the slope angle as a single variable, there is a single upheaval for a slope angle of 40° and 50° and a double upheaval at 60° and 70°. The formation mechanism of the upheaval is analyzed based on the Mohr-Coulomb criterion and considered properties of the material. The apparent friction coefficient of a flowslide is spatially and lithologically different and increases nonlinearly as the slope angle increases. The initial benchmark of the slope angle and apparent friction coefficient curve are affected by the friction coefficient of the material; the position of the inflection point at which the curve increases rapidly is affected by the coefficient of velocity restitution.

The geological setting, cave formation, and stratigraphy of the fossil-bearing deposits at Sterkfontein Caves

Understanding the formation of the Sterkfontein Caves is critical for interpreting the geologic age and patterns of accumulation of the fossils found there. The complex stratigraphy of the caves has been investigated for decades, often yielding conflicting interpretation. Current research at Sterkfontein aims to apply new mutlidisciplinary stratigraphic analyses to new stratigraphically sensitive excavations, thereby providing high-resolution contextual support to recovered assemblages and attempts to increase our understanding of excavated deposit morphology through identification and study of sedimentary and stratigraphic features preserved in the remnants of previous excavations. The Sterkfontein deposits separated into six members, Member 1 to Member 6, of which Member 2, 4, and 5 have yielded hominin remains. Partial collapses and localized erosion of deposits are common, and the spaces created are often filled with sediments from distinct sources, complicating interpretation. This is especially the case with Members 4 and 5. Characterizing taxonomic, morphological, or cultural variability from excavated deposits where no stratigraphy was recognized is difficult but is the subject of ongoing work.

Large-scale flume modelling of segregation processes in debris flows

<p>Debris flows are powerful natural hazards posing risk to life, infrastructure, and property.  Understanding the particle scale interactions in these flows is a key component in the development of models to predict the mobility, distal reach, and hazard posed by a given event. In this study we focus on the process of segregation in debris flows, using a large-scale landslide flume to explore segregation in mixtures of 25 mm, 12 mm, 6 mm, and 3 mm diameter particle sizes. Sample volumes, consisting of a multicomponent mixture of materials, up to 1 m<sup>3</sup> in size are released at the top of a 6.8 m long, 2.1 m wide slope, inclined at 30 degrees to the horizontal to initiate flow. Subsequent analysis is completed to determine the extent of vertical and longitudinal segregation of the post-landslide deposit morphology. A range of experimental strategies are explored to provide quantitative measures of particle segregation. Particle size is identified via image analysis and various techniques are applied for the longitudinal sectioning of the deposit, using measurements of segregation at the sidewall of the transparent flume, contrasted with planes measured from within the centre of the deposit. Further, replicate experiments are shown to quantify the probabilistic variation in segregation for multicomponent mixtures of dry granular flows, as well as initially saturated granular flows, to explore the effect of pore fluid on segregation processes.</p>

Electrodeposition study of the Cu-Zn-Mo system in citrate/sulfate medium

Alloys and composites that contain molybdenum have been studied due to their excellent properties, such as corrosion resistance and catalytic activity. In this work, the parameters for Cu-Zn-Mo system electrodeposition were studied, such as deposition potentials and concentration of electroactive species. The deposition potentials were examined using cyclic voltammetry and anodic linear stripping voltammetry (ALSV), the deposit morphology was evaluated using scanning electron microscopy (SEM) and crystallographic characterization was carried out for X-ray diffraction (XRD). The voltammetry studies indicated co-deposition of the metals in potentials more negative than -1.2 V, and a potential deposition at -1.5 V was chosen. The coatings presented morphology compact with small agglomerated particles with cauliflower structures, and the content of molybdenum, copper, and zinc ranged from 5 to 8%, 30 to 40% and 20 to 28%, respectively.