The loss of geological memory of past catastrophes: the case of Pompeii

In 79 A.D. Vesuvius buried entire cities in a few days under a blanket of pumice and ashes. It was a sudden event, which occurred after centuries of inactivity, heralded only by earthquakes that repeated periodically, for many years, creating addiction rather than alarm. After the event, the vegetation covered the volcanic products, and the memory of the disaster was lost. The first excavations began in Herculaneum in 1738 and in Pompeii ten years later, in times when archeology still did not exist. Much was destroyed, given away, thrown away. Almost intact buildings emerged, with all their contents, with many inhabitants caught on the run. The arduous process of recovering the sites has had important and not always happy stages, accompanied by continuous progress in the excavation methods. Volcanology has drawn from those experiences as much as it could, setting itself the goal of reconstructing the story of an explosive eruption, the first in the world to be described, by Pliny the Younger, the one that most left its mark on buildings, vegetation, animals and humans. Without the eruption, Pompeii and Herculaneum would have disappeared. The details on how the romans lost their lives in the tragedy is an important component to be offered to Pompeii’s visitors and that is at present largely imperfect. Knowing it and reconstructing its impact on people and the territory, going beyond the archaeological site, is an experience of the past and a warning for today and for the future.

Geomorphological hazard at some area of the Outer Dieng Volcanic Complex post explosive eruption era

Dieng area as an important and productive area needs the support of various aspects in encouraging regional growth and development. This region also has been experiences many disasters year by year. Disasters due to volcanism are events that cause many losses, especially casualties in the past. Discussions about potential disasters in the Dieng area should not only be limited to volcanism and earthquakes as hazards caused by endogenous processes. The Dieng area is an old landscape. As an old landscape that is heavily influenced by exogenous factors from a wet tropical climate, other potential hazards in the form of geomorphological hazards also need attention. In fact, there are some geomorphological hazards that occur due to the complexity of the landforms of this area, there are various processes that often occur such as mass movement and erosion and these processes usually have a negative impact on social and economic life. This paper aims to analyze the various types and levels of geomorphological hazards that exist outside of the Dieng Volcanic Complex. This region has experienced major eruptions in the past. At present, in the post-explosive era, it is necessary to know whether geomorphological hazards are limited to eruptions or if other hazards are a bigger threat. The terrain survey method or geomorphological survey is a field observation method used to achieve research objectives. The interpretation of remote sensing images, literature research, and documentation provides support in the form of additional data to complement the primary data from the observation. The results obtained show that the area of the Dieng Volcanic Complex after the explosive eruption era, which is largely composed of volcanic landforms, which physically dominates the denudation process. The denudation process is what causes mass movement and erosion to emphasize that there is a very high potential geomorphological hazard in this research location. This research area is also a productive agricultural production area. Although it cannot be separated from criticism because of its negative impact on the environment, because in the use and management of land carried out by the community it affects mass movement and erosion. Therefore, information on geomorphological hazards is very important to be provided and updated continuously in the interest of ensuring effective and sustainable disaster management.

Eruption Sequences and Characteristics of Weizhou Island Volcano, Guangxi Province, South of China

Weizhou island, located in the north margin of the South China Sea (SCS), is characterized by multi-stage volcanism, several eruption styles and eruption craters, and is also the youngest Quaternary volcanic island in China. An eruption on this island may pose high risk to life and property. However, the eruptive history of Weizhou island, the craters number and location, and their eruptive sequence and characteristics are still being debated, which are important for potential volcanic hazard assessment. In the present study, field surveys, 40Ar/39Ar and 14C geochronological studies and whole rock composition analysis of volcanic rock are used to investigate the eruption sequences associated with Weizhou island and the characteristics of each period. Four volcanoes were discovered at Henglushan, Hengling, Nanwan and Daling. The Henglushan and Hengling volcanoes were produced by early weak explosive and late effusive eruptions, and lavas from these volcanoes represent the foundation of island. Conversely, the Nanwan and Daling volcanoes are linked to multiple explosive eruption phases, with hydromagmatic eruptions in the first and last phase and a magmatic explosive eruption in the second phase. The pyroclastic density currents (PDCs) deposits of the Nanwan and Daling volcanoes virtually cover the entire island. Volcanic activity in Weizhou island started in Early Pleistocene and ended in Late Pleistocene. This can be divided into the following distinct periods: 1,420–1,260, 870–740, 600–480, 283–222 ka, and 33.7–13 ka. The first four periods were dominated by effusive eruptions associated with the Henglushan and Hengling volcanoes, which peaked between 870 and 740 ka. After this period, explosive eruptions began at around 33.7 ka because of magma–water interactions. These explosive eruptions then created the Nanwan and Daling volcanoes. Early effusive lava flows in Weizhou island are characterized by basaltic compositions and are linked with a small amount of fractional crystallization. Magmas in later eruptions contained slightly lower SiO2 and involved some basanite. Fractional crystallization was also less pronounced in these lavas because of their rapid ascent.

The Identification and Analysis of Gas-Related Volcanic Features within Chang’e-5 Landing Region

Chang’e-5 (CE-5) successfully landed on the young basalts area in the northeastern Oceanus Procellarum on 1 December 2020. Recent studies on the CE-5 landing area have shown that the lack of gas-related volcanic morphology indicates that the volatile elements captured in the interior of the Moon within late-stage magma is relatively low. Typical lunar gas-related volcanic features include dark mantle deposits, volcanic pits, irregular mare patches and so on. Based on orbital images, topography, and spectral data obtained from multiple missions restricted by the morphologic and compositional characteristics of typical volcanic explosive features, this study investigated the morphological characteristics of the volcanic features in detail and found that there are three dark mantle deposits (DMDs) near the source area of Rima Mairan that have unusually low albedo and abnormally high titanium and iron content than those of the surrounding material. Combined with M3 spectral analysis, it is shown that DMDs contain some volcanic glass components, which indicates a gas-rich explosive eruption process. In addition to DMDs, irregular mare patches (IMPs) and a volcanic depression/pit have been recognized in this area, both of which indicate a history of gas-related volcanic eruptions. Based on this study and combined with past studies, we determined the volcanic history in the source area of Rima Mairan, including both effusive and explosive volcanic activities.

Petrography and Mineral Chemistry of Monte Epomeo Green Tuff, Ischia Island, South Italy: Constraints for Identification of the Y-7 Tephrostratigraphic Marker in Distal Sequences of the Central Mediterranean

The 56 ka Monte Epomeo Green Tuff (MEGT) resulted from the largest volume explosive eruption from Ischia island (south Italy). Its tephra is one of the main stratigraphic markers of the central Mediterranean area. Despite its importance, a detailed characterisation of the petrography and mineral chemistry of MEGT is lacking. To fill this gap, we present detailed petrographic description and electron microprobe mineral chemistry data on samples collected on-land from the MEGT. Juvenile clasts include pumice, scoria, and obsidian fragments with porphyritic/glomeroporphyritic, vitrophyric, and fragmental textures. The porphyritic index is 13–40 vol.%, and phenocryst phases include alkali-feldspar, plagioclase, clinopyroxene, ferrian phlogopite, and titano-magnetite, in order of decreasing abundance; accessory phases include sphene, hydroxy-fluor-apatite, and rare edenite. Plagioclase varies from predominant andesine to subordinate oligoclase, whereas alkali-feldspar is more variable from sanidine to anorthoclase; quasi-pure sanidine commonly occurs as either rim or recrystallisation overgrowth of large phenocrysts due to hydrothermal alteration. Secondary minerals include veins and patches of carbonate minerals, Fe-Mn oxyhydroxides, clay minerals, and zeolites. Clinopyroxene is ferroan diopside (En45–29Fs7–27) and never reaches Na-rich compositions. This feature allows the discrimination of MEGT from aegirine-bearing, distal tephra layers erroneously attributed to MEGT, with implications for the areal distribution of Ischia explosive deposits.