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Topic Review
"Zorbas" on Southeastern Sicily
Over the last few years, several authors have presented contrasting models to describe the response of boulders to extreme waves, but the absence of direct observation of movements has hindered the evaluation of these models. The recent development of online video-sharing platforms in coastal settings has provided the opportunity to monitor the evolution of rocky coastlines during storm events. In September 2018, a surveillance camera of the Marine Protected Area of Plemmirio recorded the movement of several boulders along the coast of Maddalena Peninsula (Siracusa, Southeastern Sicily) during the landfall of the Mediterranean tropical-like cyclone (Medicane) Zorbas. Unmanned autonomous vehicle (UAV) photogrammetric and terrestrial laser scanner (TLS) surveys were performed to reconstruct immersive virtual scenarios to geometrically analyze the boulder displacements recorded in the video. Analyses highlighted that the displacements occurred when the boulders were submerged as a result of the impact of multiple small waves rather than due to a single large wave. Comparison between flow velocities obtained by videos and calculated through relationships showed a strong overestimation of the models, suggesting that values of flow density and lift coefficient used in literature are underestimated.
  • 1.6K
  • 25 Aug 2021
Topic Review
Expert System for Earthquake Prediction
Earthquake is one of the most hazardous natural calamity. Many algorithms have been proposed for earthquake prediction using expert systems (ES). We aim to identify and compare methods, models, frameworks, and tools used to forecast earthquakes using different parameters. The analysis shows that most of the proposed models have attempted long term predictions about time, intensity, and location of future earthquakes. An investigation on different variants of rule-based, fuzzy, and machine learning based expert systems for earthquake prediction has been presented. Moreover, the discussion covers regional and global seismic data sets used, tools employed, to predict earth quake for different geographical regions. Bibliometric and meta-information based analysis has been performed by classifying the articles according to research type, empirical type, approach, target area, and system specific parameters.
  • 1.6K
  • 03 Feb 2021
Topic Review
Age of the Earth
The age of the Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age may represent the age of the Earth's accretion, or core formation, or of the material from which the Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples. Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. The oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Calcium–aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.567 billion years old, giving a lower limit for the age of the Solar System. It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the time this accretion process took is not yet known, and predictions from different accretion models range from a few million up to about 100 million years, the difference between the age of Earth and of the oldest rocks is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
  • 1.5K
  • 21 Nov 2022
Topic Review
Marine Nepheloid Layer
Marine nepheloid layer is a turbid layer containing significantly more suspended particles than the adjacent layers in oceans. The suspended particles may collide and form large falling particle aggregates known as marine snow. Although the nepheloid layer continually changes with time and space, it shows certain temporal and spatial stability. A marine nepheloid layer could last a few days to years, with a thickness ranging from meters to kilometers.
  • 1.4K
  • 16 Mar 2022
Topic Review
Saline Lakes
Saltwater lakes around the world are drying at a rapid rate. These lakes are present in arid and semi-arid regions where evaporation exceeds precipitation. The Aral Sea and Lake Urmia are examples for such rapidly drying lakes. These two lakes have lost up to 90% of their former area in the past 50 years.  
  • 1.4K
  • 28 Oct 2020
Topic Review
Agate
Agate ‒ a spectacular form of SiO2 and a famous gemstone ‒ is commonly characterized as banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated with macro-crystalline quartz, quartzine, opal-C, opal-CT, cristobalite and/or moganite. In addition, agates often contain considerable amounts of mineral inclusions and water as both interstitial molecular H2O and silanol groups.
  • 1.4K
  • 16 Apr 2021
Topic Review
Water Footprint
The water footprint (WF) is a widely recognised and comprehensive indicator of both the direct and indirect appropriation of freshwater. It has been utilised for diverse functions, including as a key indicator of the planetary boundaries and United Nations Sustainable Development Goals. (draft for definition)
  • 1.4K
  • 03 Feb 2022
Topic Review
Cenozoic Basins-evolution Eastern-External Betic Zone
Four main unconformities (1-4) were recognized in the sedimentary record of the Cenozoic basins of the eastern External Betic Zone. More in detail, they are located at different stratigraphic levels as follows: (1) Cretaceous-Paleogene boundary even if this unconformity was also recorded at the early Paleocene (Murcia sector) and early Eocene (Alicante sector); (2) Eocene-Oligocene boundary and quite synchronous in the whole considered area; (3) early Burdigalian, and quite synchronous (recognized in the Murcia sector); (4) middle Tortonian (recognized in Murcia and Alicante sectors). These unconformities correspond to stratigraphic gaps of different temporal extensions with different meanings, which allowed recognizing minor sedimentary cycles in the Paleocene-Miocene time span. The Cenozoic marine sedimentation started over the oldest unconformity (i.e. the principal one), above the Mesozoic marine deposits. Paleocene-Eocene sedimentation shows numerous tectofacies (such as: turbidites, slumps, olistostromes, mega-olistostromes and pillow-beds) interpreted as related to an early, blind and deep-seated tectonic activity, acting in the more internal subdomains of the External Betic Zone as a result of the geodynamic processes related to the evolution of the westernmost branch of the Tethys. The second unconformity resulted from a Oligocene to Aquitanian sedimentary evolution in the Murcia Sector from marine realms to continental environments. This last time interval is characterized as the previous one by a gentle tectonic activity. On the other hand, the Miocene sedimentation was totally controlled by the development of superficial thrusts and/or bend zones of strike-slip faults both related to the regional geodynamic evolutionary framework linked to the Mediterranean opening. These bends of strike-slip faults created subsidence areas (pull-apart basin-type) and affected the sedimentation lying above the third unconformity. By contrast, the subsidence areas were bounded by structural highs affected by thrusts and folds. After the third unconformity, the Burdigalian-Serravallian sedimentation occurred mainly in shallow- to deep-water marine environments (Tap Fm). During the late Miocene, after the fourth unconformity, the activation of the bend zones of strike-slip faults caused a shallow marine environment sedimentation in the Murcia sector and a continental (lacustrine and fluvial) deposition in the Alicante sector represented, the latter resulting in alluvial fan deposits. Furthermore, the location of these fans changed over time according to the activation of faults responsible for the tectonic rising of Triassic salt deposits, which fed the fan themselves.
  • 1.3K
  • 10 Oct 2020
Topic Review
Impact of High-Temperature Treatment on Granite
Temperature changes have significant effects on rock properties. The changes in properties vary for different rocks with different temperature ranges. Granite is an igneous type of rock that is common in India and is frequently used for construction and domestic purposes. Granite is mainly composed of quartz and feldspar and shows a considerable response to temperature changes. The heating effects of granite on its physical and mechanical properties become increasingly pronounced with increasing pick temperatures. 
  • 1.2K
  • 29 Nov 2022
Topic Review
Jáchymov
Jáchymov (Czech pronunciation: [ˈjaːxɪmof]); German: Sankt Joachimsthal or Joachimsthal) is a spa town in Karlovy Vary District in the Karlovy Vary Region of the Czech Republic. It has about 2,300 inhabitants. The historical core of the town from the 16th century is well preserved and protected by law as urban monument zone. It is a comprehensive set of Gothic–Renaissance patrician houses. Jáchymov has a long mining tradition, thanks to which it used to be the second most populous town in the Kingdom of Bohemia in 1534. At first silver was mined here. The silver Joachimsthaler coins minted here since the 16th century gave their name to the Thaler and the dollar. After the Wieliczka Salt Mine ceased industrial exploitation in 2007, the Svornost mine (1525) became the oldest mine still in use in Europe. It is also the first and for a long time the only mine in the world, where radium was mined. The mining cultural landscape of Jáchymov is a UNESCO World Heritage Site as a part of the Ore Mountain Mining Region.
  • 1.1K
  • 04 Nov 2022
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