Search Results (13)

Some previous studies have already highlighted the importance of Quaternary sediments as geoheritage, although the related knowledge remains incomplete and geographically biased. Unique Quaternary features are often overlooked in areas famous for their pre-Quaternary geoheritage. Moreover, the already established high-value linked to pre-Quaternary phenomena require comprehensive descriptions; therefore, it is reasonable to analyze the related Quaternary features (even if these are only locally unique). For the purposes of the present study, three localities that form parts of larger geosites, and which represent Quaternary sediments of Mountainous Adygeya in the Western Caucasus, are characterized. They are assessed qualitatively, with a general description of sediments and attention paid to their origin, potential scientific importance, and accessibility. The Rufabgo Canyon hosts colluvial megaclast sediments. The Dakh–Sakhray Confluence exhibits typical alluvial sediment where detrital clasts are mixed with rather numerous Fe-rich concretions washed out from the parent rocks. The Stonesea Range exhibits mixed eluvial–deluvial sediment formed as a result of the karstification of carbonates and the erosion of overlaying red siliciclastics. All these sediments are of interest to scientists because they can be employed for promising research projects, revealing the peculiarities of the local patterns of Quaternary sedimentation. The localities under consideration are geoheritage points within the larger geosites and are perfectly accessible. Aside from their use by scientists, these localities can potentially be used by geosciences educators to train university students in sedimentology. In two cases, the sediments are also aesthetically important for attracting tourists. Generally, Quaternary sediments should be considered together with the other unique features represented in the geosites of Mountainous Adygeya. Full article

The detachment and mobilization of boulders from rocky shore platforms by waves involves complex geomorphic and hydrodynamic processes. Understanding these processes requires precise information on the rates and patterns of movement of these megaclasts scaled against the wave conditions that generate boulder mobility. Repeat photogrammetry and structure-from-motion (SfM) models commonly used in geomorphic analyses are an interesting option for monitoring boulder dynamics. In this study, we used unmanned aerial vehicle (UAV)-based digital photogrammetry and SfM differential models to identify recent boulder movements over a rocky shore platform in Laghdira, Morocco. Combining these results with data on storm occurrence in the study area allowed us to identify storm waves as the unique driver of the dislodged and mobilized boulders. The identified storm event had a significant wave height of 5.2 m. The UAV models were built from imagery captured in September and December 2019 using a DJI MAVIC PRO PLATINUM, and we used QGIS to produce 2D and 3D model outputs. The exploitation of the 2D model differentials allowed us to appreciate the response of the boulders to the storm waves and to determine platform volumetric changes and, therefore, boulder mobility. The 3D models were valuable in determining the mode of transport of the boulders. Mobility patterns included sliding, overturning with no further mobility, and rotation and saltation, as well as boulder breakup. Storm waves did not have a preferential impact on any particular boulder shape, size category, or position at the outer edge of the platform. These results highlight the utility of combining UAV surveys with identified storm events, which are much more frequent than tsunamis, in determining observed boulder initiation and mobility. Full article

New investigations in the Western Caucasus contribute to the understanding of granite pseudokarst (sensu lato) and megaclasts linked to river erosion. A plot on the bank of the Belaya River (Mountainous Adygeya, Western Caucasus) was selected to examine diverse and abundant pseudokarst features (small rock basins, hollows, potholes, and channels) and large clasts. Morphological analysis of these features clarifies their general characteristics and genetic interpretations. Pseudokarst features can be classified into two major categories, namely the relatively small (<1 m) and large (>1 m) features. Potholes, which are usually 1–3 m in size, are the most characteristic features occurring on two levels, i.e., on steep walls of the gorge (half-filled with river water) and on slightly inclined surfaces of a terrace-like landform (subaerial exposure). In both cases, their walls from the side of the river are broken. Apparently, these potholes were formed on the river bottom. Subsequent incision of the gorge elevated potholes and the river has eroded them from one side. Apparently, some pseudokarst features are related to macroturbulent flood flows and granite weathering. Due to its scientific uniqueness and aesthetic attractiveness, this granite pseudokarst constitutes geoheritage, which can be exploited for the purposes of geoscience research and geotourism development. Full article

Geoheritage is not necessarily linked genetically to “purely” geological processes. Investigations in two urban areas of Russia allowed us to find essentially artificial objects demonstrating certain geological uniqueness. The huge balls sculptured from rapakivi granite and installed in Saint Petersburg represent cultural, historical, and stone heritage. These are also artificial megaclasts with perfect sphericity. The coal waste heaps situated in Shakhty and its vicinity represent industrial, historical, and urban heritage. These are also artificial landforms creating a kind of pseudo-mountainous landscape. These examples permit us to question the importance of the co-occurrence of heritage categories for geosite assessment. Full article

This study investigates gravity-induced landforms that populate the North-Eastern coast of Malta. Attention is focused on tens of persistent joints and thousands of boulders associated with deep-seated gravitational slope deformations (DGSDs), such as lateral spreads and block slides. Lateral spreads produce deep and long joints, which partially isolate limestone boulders along the edge of wide plateaus. These lateral spreads evolve into large block slides that detach thousands of limestone boulders from the cliffs and transport them towards the sea. These boulders are grouped in large slope-failure deposits surrounding limestone plateaus and cover downslope terrains. Gravity-induced joints (n = 124) and downslope boulders (n = 39,861) were identified and categorized using Google Earth (GE) images and later validated by field surveys. The datasets were digitized in QGIS and stored using ESRI shapefiles, which are common digital formats for storing vector GIS data. These types of landslides are characterized by slow-moving mechanisms, which evolve into destructive failures and present an elevated level of risk to coastal populations and infrastructure. Hundreds of blocks identified along the shore also provide evidence of sinkholes; for this reason, the paper also provides a catalogue of sinkholes. The outputs from this research can provide coastal managers with important information regarding the occurrence of coastal geohazards and represent a key resource for future landslide hazard assessment. Full article

Megaclast research has intensified recently, and its further development needs new factual information from various places of the world. Three new megaclast localities are reported from the Russian South, namely, Shum, Merzhanovo, and the Red Stones. These localities host blocks of all grades, sometimes with certain flatness and angle roundness. Megaclasts from Shum and Merzhanovo result from poly-phase slope processes. At the Red Stones locality, a group of residual megaclasts will appear in the future due to weathering processes. This evidence together with the examples brought by the virtual journeys and the literature interpretations prove the genetic diversity of megaclasts and stress the urgency of their further investigations in various depositional environments. Full article

The aim of this study is to demonstrate the advantages of using micro drones in the study of large slow-moving landslides, which are widespread along the northwestern coast of Malta. In particular, attention was given to the inventory and analysis of gravity-induced joints and megaclast deposits at four study sites selected due to the presence of remarkable examples of lateral spreads evolving into block slides. The research was carried out by means of Google Earth (GE) image analysis and uncrewed aerial vehicle digital photogrammetry (UAV-DP). UAV-DP outputs enabled the identification and characterization of tens of persistent joints (locally exceeding 150 m) and permitted the size categorization of thousands of blocks. With reference to gravity-induced joints, a favorable agreement was found between existing datasets (mainly based on the integration of GE analysis and field survey) and UAV-DP outputs in terms of the identification of joints and their persistence. Conversely, the use of the UAV-DP technique showed significant advantages in terms of joint aperture determination (even exceeding 1 m) and distribution setting. Regarding the extensive megaclast deposits, UAV-DP enabled the identification of 8943 individuals which, compared with the 5059 individuals identified by GE analysis, showed an increase in the total population of 76%. This is related to the high accuracy of DP-derived orthomosaics and 3D models, which are particularly useful for identifying detached blocks. The inexpensive technique used in this research highlights its potential for being extended to other rocky coastal areas affected by slow-moving landslides. Full article

The Żonqor coastline, southeast Malta, displays an exceptional range of geomorphic signatures of extreme coastal events. This paper brings together evidence acquired from a field survey, analysis of time-sequential imagery, and hydrodynamic modelling to investigate the histories of boulder groups identified by their intrinsic and contextual characteristics. Clear differences are revealed between the distribution of boulders recently moved and those of considerable age. Tracking the movement of boulders since 1957 confirms that storms of surprisingly frequent interval are capable of complex boulder movements, including lifting of megaclasts. Scrutiny of the ancient boulders, including weathering features and fascinating landward-facing (reverse) imbrication, cautiously suggests tsunami as the agent for their emplacement. A novel method is developed for depicting the velocity decay profiles of hypothetical waves, which overcomes some of the limitations of the Nott approach. Applied here, the wave run-up context further sets the ancient movers apart from their recent mover companions. The combined evidence implies a palimpsestic landscape where storm waves are regular geomorphic agents that add to and rework the distribution of boulders close to the shoreline, but over long time periods the landscape becomes reset by tsunami—a concept that is of value to agencies in Malta responsible for coastal safety, planning and management. Full article

True diversity of geological heritage sites (geosites) is yet to be fully understood. New field studies of the Khadzhokh Canyon and its vicinities in the Western Caucasus (Mountainous Adygeya tourist destination, southwestern Russia) have allowed characterizing its geoheritage. Multiple unique features are assigned to geomorphological, stratigraphical, paleontological, palaeogeographical, sedimentary, tectonic, hydro(geo)logical, and coupled economical and geoexplorationgeoheritage types. This geoheritage is highlycomplex, and its rank is national. The unique features include (but not limited to) three canyons, Triassic stratigraphical sections, Late Jurassic coral reef, megaclast accumulations, chevron folds, and waterfalls. The geoheritage is distributed along the Khadzhokh Canyon and its branches. The configuration of thisgeositemakes it possible to propose a new category, namely dendritic geosites distinguished by continuous occurrence of geoheritage via branching stripes. Such geosites can be either natural (determined by dendritic drainage network and deep valley incision) or anthropogenic (determined by dendritic road network with lengthy road cuttings). In the former case, geosites are also geomorphosites and host viewpoint geosites. Full article

Coastal megaclast deposits are dominated by detrital particles larger than 1 m in size. These attract significant attention of modern researchers because of the needs of sedimentary rock nomenclature development and interpretation of storm and tsunami signatures on seashores. If so, finding localities that exhibit coastal megaclast deposits is an important task. Field studies do not offer a quick solution, and, thus, remote sensing tools have to be addressed. The application of the Google Earth Engine has permitted to find four new localities, namely Hondarribia in northern Spain (Biscay Bay), the Ponza Island in Italy (Tyrrhenian Sea), the Wetar Island in eastern Indonesia (Banda Sea), and the Humboldt o Coredo Bay at the Colombia/Panama border (eastern Pacific). In these localities, coastal megaclast deposits consisting of blocks (1–10 m in size) and some megablocks (>10 m in size) are delineated and preliminary described in regard to the dominant size of particles, package density, mode of occurrence, etc. The limitations of such virtual surveys of coastal megaclast deposits are linked to an insufficiently high resolution of satellite images, as well as ‘masking’ effects of vegetation cover and cliff shadows. However, these limitations do not diminish the importance of the Google Earth Engine for finding these deposits. Consideration of some tourism-related information, including photos captured by tourists and bouldering catalogues, facilitates search for promising areas for subsequent virtual surveying of megaclast distribution. It is also established that the Google Earth Engine permits quantitative analysis of composition of coastal megaclast deposits in some areas, as well as to register decade-long dynamics or stability of these deposits, which is important to interpret their origin. The current opportunities for automatic detection of coastal megaclast deposits seem to be restricted. Full article

Nature-based tourism is stimulated by the aesthetic properties of landscapes, and particular elements of the latter determine the overall scenic beauty. Big stones on forested mountain slopes are among such elements. The Partisan Glade geosite-based tourist destination ofthe Western Caucasus in southwestern Russia is distinguished by the occurrence of such stones. Their field investigation (measurements of physical parameters and interpretation of the common criteria of tourist-meaningful beauty) shows that these are essentially blocks (clasts with the size of 1–10 m) of all grades (fine, medium, and coarse blocks) and colluvial origin. The blocks influence on such parameters of scenic beauty as scale, condition, balance, diversity, shape, and uniqueness, and, therefore, these blocks are of aesthetic value. The most important is color and size. Apparently, the presence of these big stones stimulates tourists’ positive emotions. It is recommended to avoid block removal or breaking in the course of road maintenance. Full article

The term “megaclast” started circulation near the beginning of the 21st century. The present review is aimed at examination of the use of this term in the modern geoscience literature. The main method is bibliographical survey of the articles published during 2000–2017 with the on-line bibliographical database “Scopus”. The main findings are as follows. The term “megaclast” has not been used extensively, but the number of the articles employing this term increased in the mid-2000s and in the early 2010s. The majority of the papers deal with megaclasts of Quaternary age. The megaclast research focuses on five regions, namely West Europe, Australia and New Zealand, Western North America, Southern South America, and the Pacific and circum-Pacific. The most studied are megaclasts occurring on coasts influenced by tsunamis and storms; significant attention has been paid also to those clasts transported by volcanism-triggered debris flows and slope failures, both continental and submarine. There are three serious biases relevant to the use of the term “megaclast” in the geoscience literature, namely stratigraphical, geographical, and genetic biases. Due to this incompleteness in the knowledge of megaclasts, this term should be either used more actively, which is preferable, or abandoned. Full article

Large clasts are in focus of the modern geoscience research, but their broadly-accepted classification is absent and specialists tend to over-emphasize on clasts of coastal zones. New field investigations in the Western Caucasus have permitted the finding of isolated large clasts of carbonate composition that occur above the Early–Middle Jurassic shale sequence and that are covered by modern soils. These clasts can be determined either as large boulders or megaclasts (blocks) depending on the preferred classification. Their shape is chiefly irregular, although smoothened surfaces and rounded angles (resulting from previous karstification) are also registered. These large clasts are located quite far from the natural outcrops of the Late Jurassic carbonates, which are their parent rocks. The origin of these clasts can be linked to collapses of the Pleistocene cliff of a cuesta-type mountain range, which later retreated to its present position. The evidence from the study area implies the size of 1 m or 2 m as a plausible criterion for distinction of boulders and megaclasts, and it also makes claims towards the development of a wider genetic typology of megaclasts. Full article