Effects in North Africa of the 934-940 CE Eldgjá and 1783-1784 CE Laki eruptions (Iceland) revealed by previously unrecognized written sources

AbstractIn historic times, two catastrophic fissure eruptions originated in the Eastern Volcanic Zone of Iceland, known as Eldgjá eruption (934–940 CE) and Laki eruption (1783–1784 CE). Eldgjá produced 19.7 km3 of lava flows and 1.3 km3 of tephra; Laki emitted 14.7 km3 of lavas and 0.4 km3 of tephra. They released 232 and 122 megatons of SO2 into the atmosphere, respectively. Abundant historic descriptions of the effects of the Laki eruption indicate that the SO2 release produced a sulphuric aerosol that spread across the northern hemisphere with devastating impacts on the population and the environment, especially in Europe. In this study, we present two new written sources that enable the effects of the Eldgjá and Laki eruptions to be fixed to an exact date and place of occurrence in North Africa. These are a medieval North African chronicle known as Rawḍ al-Qirṭās, written in 1326 CE and describing events in Morocco, and a chronicle of events in the island of Djerba (southern Tunisia), written by Muhammad b. Yusef al-Musabi in 1792–1793 CE. These previously unrecognized sources describe in detail the fading of sunlight coupled with the persistent presence of a thick fog made up of fine particles carried over from long distances. The chronicles report events in Morocco in the time period October 938–October 939 CE, and in Tunisia in the year 1783 CE. These data can be interpreted as the first detailed evidence of the consequences of the Eldgjá and Laki eruptions in North Africa. They also can be helpful in dating and determining the area of influence of the eruptions; this may be useful for several applications, such as the numerical simulation of these events, or hazard planning in case of possible future similar eruptions from the same Icelandic area

Rifting Kinematics Produced by Magmatic and Tectonic Stresses in the North Volcanic Zone of Iceland

In the North Volcanic Zone of Iceland, we studied with the greatest possible detail the complete structural architecture and kinematics of the whole Theistareykir Fissure Swarm (ThFS), an N-S-trending, 70 km long active rift. We made about 7500 measurements along 6124 post-Late Glacial Maximum (LGM) extension fractures and faults, and 685 pre-LGM structures. We have collected the data over the last 6 years, through extensive field surveys and with the aid of drone mapping with centimetric resolution. In the southern sector of the study area, extension fractures and faults strike mainly N10°-20°, the opening direction is about N110°, and the dilation amount is in the range 0.1–10 m. In the central sector, faults and extension fractures strike mainly N00-10°, the opening direction is N90-100°, and the dilation amount is 0.1–9 m. In the northern sector, extension fractures and faults strike N30-40°, the opening direction is about N125°, and the dilation amount is 0.1–8 m. The variations in strike are attributable to two processes: the interaction with the WNW-ESE-striking Husavik-Flatey transform fault and Grímsey Oblique Rift (Grímsey lineament), and the structural inheritance of older NNE- to NE-striking normal faults. Most extension fractures show a minor strike-slip component: a systematic right-lateral component can be accounted for by the interaction with the WNW-ESE-striking fault zones and the regional, oblique opening of the rift. We regard dyke propagation as a possible cause for the more complex strike-slip components measured at several other fractures. Cumulated dilation and fracture frequency decrease along the rift with distance away from the Theistareykir volcano, situated in the central sector of the ThFS. This is interpreted as a decrease in the number of dykes that are capable of reaching great distances after being injected from the magma chamber

Landslides near Enguri dam (Caucasus, Georgia) and possible seismotectonic effects

The Enguri dam and water reservoir, nested in the southwestern Caucasus (Republic of Georgia), are surrounded by steep mountain slopes. At a distance of 2.5 km from the dam, a mountain ridge along the reservoir is affected by active deformations with a double vergence. The western slope, directly facing the reservoir, has deformations that affect a subaerial area of 1.2 km2. The head scarp affects the Jvari–Khaishi–Mestia main road with offsets of man-made features that indicate slip rates of 2–9 cm yr−1. Static, pseudostatic and Newmark analyses, based on field and seismological data, suggest different unstable rock volumes based on the environmental conditions. An important effect of variation of the water table is shown, as well as the possible destabilization of the slope following seismic shaking, compatible with the expected local peak ground acceleration. This worst-case scenario corresponds to an unstable volume on the order of up to 48±12×106 m3. The opposite, eastern slope of the same mountain ridge is also affected by wide deformation affecting an area of 0.37 km2. Here, field data indicate 2–5 cm yr−1 of slip rates. All this evidence is interpreted as resulting from two similar landslides, whose possible causes are discussed, comprising seismic triggering, mountain rapid uplift, river erosion and lake variations

Landsliding near Enguri dam (Caucasus, Georgia) and possible seismoectonic effects

The Enguri dam and water reservoir, nested in southwestern Caucasus (Republic of Georgia), are surrounded by steep mountain slopes. At a distance of 2.5 km from the dam, a mountain ridge along the reservoir is affected by active deformations with a double vergence. The western slope, directly facing the reservoir, has deformations that involve a subaerial area of 1.2 km2. The head scarp interests the main Jvari-Khaishi-Mestia road with offset of man-made features that indicate slip rates of 2-9 cm/y. Static, pseudostatic and Newmark numerical analyses, based on field and seismological data, suggest different unstable rock volumes basing on the environment conditions. An important effect of variation of water table is showed, as well as the possible destabilization of the landslide following seismic shaking compatible with the expected local Peak Ground Acceleration. This worst scenario corresponds to an unstable volume in the order of up to 48 ± 12*106 m3. The opposite, eastern slope of the same mountain ridge is also affected by wide deformation involving an area of 0.37 km2. Here, field data indicate 2-5 cm/y of short-term and long-term slip rates. Ground Penetrating Radar surveys of the head scarps confirm that these slip planes are steep and extend downward. All these evidences are interpreted as resulting from two similar landslides, whose possible causes are discussed, comprising seismic triggering, mountain rapid uplift, river erosion and lake variations

The impact of morning stiffness duration on the definition of clinical inactive disease in juvenile idiopathic arthritis

Objective To investigate the impact of morning stiffness (MS) on parent disease perception in children with juvenile idiopathic arthritis (JIA) with clinical inactive disease (CID). Methods 652 visits in which patients fulfilled 2004 or 2011 Wallace criteria for CID were examined. Parent-reported outcomes were compared among patients with no MS or with MS < or 65 15 minutes. Results Among 652 visits with CID by 2004 criteria, no MS was reported in 554 visits (85%), MS < 15 minutes in 53 (8%), and MS 65 15 minutes in 45 (7%). The frequency of altered physical function, health-related quality of life, and well-being, pain and disease activity visual analog scales was proportionally greater from patients without MS to those with longer MS. The frequency of parent subjective rating of disease state as remission was 87.7%, 58% and 27.7% among patients with no MS, MS < 15 minutes and MS 65 15 minutes, respectively. Conclusion Our results suggest that a change in 2011 CID criteria to require absence of MS should be considered

The DEM or Mt. Etna: geomorphological and structural implications

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Integrating virtual reality and GIS tools for geological mapping, data collection and analysis: an example from Metaxa Mine, Santorini (Greece)

In the present work we highlight the effectiveness of integrating different techniques and tools for better surveying, mapping and collecting data in volcanic areas. We use an Immersive Virtual Reality (IVR) approach for data collection, integrated with Geographic Information System (GIS) analysis in a well-known volcanological site in Santorini (Metaxa mine), a site where volcanic processes influenced the island’s industrial development, especially with regard to pumice mining. Specifically, we have focused on: (i) three-dimensional (3D) high-resolution IVR scenario building, based on Structure from Motion photogrammetry (SfM) modeling; (ii) subsequent geological survey, mapping and data collection using IVR; (iii) data analysis, e.g., calculation of extracted volumes, as well as production of new maps in a GIS environment using input data directly from the IVR survey; and finally, (iv) presentation of new outcomes that highlight the importance of the Metaxa Mine as a key geological and volcanological geosite

Modeling the electronic transport in FinFET-like lateral Ge-on-Si pin waveguide photodetectors for ultra-wide bandwidth applications

We determined the velocities of photogenerated electrons and holes in FinFET-like lateral Ge-on-Si waveguide photodetectors with Monte Carlo transport simulation. The calculated carrier velocities were used in a 3D multiphysics model focused on the investigation of the electro-optic frequency response. The good match between the bandwidths predicted by the model and the corresponding experimental values available from the literature, larger than 200 GHz, indicates the importance of moving beyond conventional drift-diffusion models for a realistic description of next-generation high-speed integrated photodetectors

Improving natural risk management by means of virtual surveys through hazardous volcanic contexts by using Augmented and Virtual Reality

To ensure an efficient natural risk management, we need an in-depth understanding and assessment of risk as well as the adoption of effective prevention measures. Modern techniques such as Augmented Reality (AR) and Virtual Reality (VR) offer the opportunity to explore our environment for professional as well as educational purposes, conveying useful information not only to scientists, but also to at-risk populations. “Virtual navigation on volcanoes by Augmented Reality and 3D-headset” was a geoevent we organized in the framework of the 6th edition of the Italian “Settimana del Pianeta Terra” (Week of Planet Earth) in October 2018. The geoevent featured AR and Virtual Reality exhibits, highlighting the benefits of these tools in applications for Earth monitoring, also with positive contributions in mitigation actions to reduce the impact of natural hazards. We proposed virtual 3D models of volcanic regions in Iceland and Italy (at Etna volcano), which guided the visitors in a virtual survey through hazardous contexts like landslide prone areas and fault zones. The event was supported as part of the 3DTeLC project funded through the Erasmus+ Key Action 2 Strategic Partnerships for Higher Education scheme (Project Reference: 2017-1-UK01-KA203-036719).3DTeLC project funded through the Erasmus+ Key Action 2 Strategic Partnerships for Higher Education scheme (Project Reference: 2017-1-UK01-KA203-036719)PublishedVienna, Austria1TM. Formazion