• Energy Research
• Geosciences close
• Energy Research close

Proximity to magma bodies is generally acknowledged as providing the energy source for hot hydrothermal reservoirs. Hence, it is appropriate to think of a “magma–hydrothermal system” as an entity, rather than as separate systems. Repeated coring of Kilauea Iki lava lake on Kilauea Volcano, Hawaii, has provided evidence of an impermeable, conductive layer, or magma–hydrothermal boundary (MHB), between a hydrothermal system and molten rock. Crystallization on the lower face of the MHB and cracking by cooling on the upper face drive the zone downward while maintaining constant thickness, a Stefan problem of moving thermal boundaries with a phase change. Use of the observed thermal gradient in MHB of 84 °C/m yields a heat flux of 130 W/m2. Equating this with the heat flux produced by crystallization and cooling of molten lava successfully predicts the growth rate of lava lake crust of 2 m/a, which is faster than simple conduction where crust thickens at t and heat flux declines with 1 / t . However, a lava lake is not a magma chamber. Compared to erupted and degassed lava, magma at depth contains a significant amount of dissolved water that influences the magma’s thermal, chemical, and mechanical behaviors. Also, a lava lake is rootless; it has no source of heat and mass, whereas there are probably few shallow, active magma bodies that are isolated from deeper sources. Drilling at Krafla Caldera, Iceland, showed the existence of a near-liquidus rhyolite magma body at 2.1 km depth capped by an MHB with a heat flux of ≥16 W/m2. This would predict a crystallization rate of 0.6 m/a, yet no evidence of crystallization and the development of a mush zone at the base of MHB is observed. Instead, the lower face of MHB is undergoing partial melting. The explanation would appear to lie in vigorous convection of the hot rhyolite magma, delivering both heat and H2O but not crystals to its ceiling. This challenges existing concepts of magma chambers and has important implications for use of magma as the ultimate geothermal power source. It also illuminates the possibility of directly monitoring magma beneath active volcanoes for eruption forecasting.

This paper explores the efficacy of the geoeducational assessment method (GEOAM) in evaluating the geoeducational potential of geosites. Leveraging a case study involving four geotopes on the island of Samos, Aegean Sea, Greece, this study examines the strengths and limitations of the GEOAM approach, aiming to comprehensively elucidate its efficacy. The assessment outcomes illuminate the vital role of targeted strategies in enhancing the educational and sustainable impact of geosites, thereby fostering geological understanding and responsible environmental engagement. A prominent finding is the urgency to address the gap in foundational geological knowledge, underscored by the need for robust geoeducation programs at schools and the augmented presence of geologists. While acknowledging potential limitations, including subjectivity in scoring and data availability constraints, this study underscores the method’s broader contribution to societal goals. By integrating geoethic principles, GEOAM offers a comprehensive framework aligning with the objectives of geological comprehension and environmentally conscious practices.

The Colorado River has flowed across the dextral strike-slip plate boundary between the North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain (between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief up to 2000 m. Satellite mapping and detailed logging reveal a variable balance between the two suites in the Olla Formation with an apparent upward increase in L-Suite units before abrupt cessation of Colorado sedimentation in the basin. Stable heavy mineral indices differentiate L-Suite (high rutile:zircon index: RZi 40–95) from C-Suite (RZi: 0–20). Both suites have garnet:zircon index (GZi) and apatite:tourmaline index (ATi) mostly above 50, although many L-suite and mixed Olla samples have much lower ATi (20–50), suggesting that the distal floodplain was wet and the local sediment had a longer residence time there, or went through several cycles of erosion and redeposition. Heavy mineral analysis, garnet geochemical analysis, and detrital zircon U-Pb age spectra allow us to quantify the amount of mixing from different sediment sources. These data show that about 30% of the mixed units are derived from the Colorado River and that up to 20% of the L-Suite is also derived from the Colorado River, suggesting that there was mutual cannibalisation of older deposits by fluvial channels in a transitional area at the basin margin. Although this study is local in scope, it provides an insight into the extent and nature of sediment mixing in a two-source system. We conclude that most ‘mixing’ is actually interbedding from separate sources; true mixing is facilitated by low subsidence rates and the rapid migration of fluvial channels.

Surfactants (i.e., solutes that reduce the surface tension of water) exist in the subsurface either naturally or are introduced to the subsurface due to anthropogenic activities (e.g., agricultural purposes, environmental remediation strategies). Surfactant-induced changes in surface tension, contact angle, density, and viscosity alter the water retention and conduction properties of the vadose zone. This research numerically investigates the effects of surfactants in the vadose zone by comparing the flow and transport of three different surfactant solutions, namely butanol, ethanol, and Triton X-100. For each surfactant case, surfactant-specific concentration-dependent surface tension, contact angle, density, and viscosity relationships were incorporated by modifying a finite element unsaturated flow and transport code. The modified code was used to simulate surfactant infiltration in the vadose zone at residual state under intermittent boundary conditions. The modelling results show that all three surfactant solutions led to unique and noteworthy differences in comparison to the infiltration of pure water containing a conservative tracer. Results indicate that surfactant infiltrations led to complex patterns with reduced vertical movement and enhanced horizontal spreading, which are a function of concentration-dependent surface tension, density, contact angle, viscosity and sorption characteristics. The findings of this research will help understanding the effects of surfactant presence in the subsurface on unsaturated flow and its possible links to future environmental problems.

Purpose: This paper entails a reflection on sustainability and specific tourism contexts (i.e., ecotourism). It focusses mainly on local communities’ determiners in the consumer’s purchase decision process in ecotourism. This research aimed at understanding the determiners in the process of consumer decisions in ecotourism contexts, as well as verifying the growing importance of ecotourism. Methodology: A questionnaire was conducted (with ecotourism specific contexts), in Portugal. Portugal is a tourist destination that has gained notoriety and recognition in recent years. In total, 197 questionnaires were collected, aiming for a deeper understanding of the real social, economic, cultural and environmental impacts resulting from the uncontrolled development of tourism. This study aimed at testing the proposed conceptual model empirically (i.e., the relationship between destination image and post-purchase behaviour). Findings: Sustainability must be looked at as a vital need for society in general, as well as for the tourism sector. Ecotourism is the natural evolution of tourism employing care for the environment, culture and local traditions, while promoting environmental education. Research Limitations: The results obtained are limited, considering the availability of most accommodation units in the ecotourism segment in Portugal (e.g., hotels). As next steps, it is advisable that hotel units come to realise the pertinence of such research as they are the main beneficiaries of these initiatives, being then recommended that they collaborate with the process of completing surveys. Originality/Value: Managers and ecotourists can use the outcomes of this study to gain an in-depth understanding of customer experiences (i.e., sustainability experiences), to develop effective marketing strategies, and to create an operational environment that can maximise customers’ perceived experiential values. Destination image plays a fundamental part in terms of experience and the tourist’s own satisfaction, with a need to improve the degree of affectivity towards the hotel unit.

As tropical glaciers continue to retreat, we need accurate knowledge about where they are located, how large they are, and their retreat rates. Remote sensing data are invaluable for tracking these hard-to-reach glaciers. However, remotely identifying tropical glaciers is prone to misclassification errors due to ephemeral snow cover. We reevaluate the size and retreat rates of the two largest tropical ice masses, the Quelccaya Ice Cap (Peru) and Nevado Coropuna (Peru), using remote sensing data from the Landsat missions. To quantify their glacial extents more accurately, we expand the time window for our analysis beyond the dry season (austral winter), processing in total 529 Landsat scenes. We find that Landsat scenes from October, November, and December, which are after the dry season, better capture the glacial extent since ephemeral snow cover is minimized. We compare our findings to past studies of tropical glaciers, which have mainly analyzed scenes from the dry season. Our reevaluation finds that both tropical ice masses are smaller but retreating less rapidly than commonly reported. These findings have implications for these ice masses as sustained water resources for downstream communities.

Climate-related geohazards, such as landslides, floods, and coastal erosion due to climate change, are increasingly impacting human settlements and activities. This study, part of the European Project RESPONSe (Interreg Italy–Croatia), investigates the perception of climate change as a catalyst of future geohazards among the citizens of the Veneto region (northeastern Italy). A total of 1233 questionnaires were completed by adult citizens and analyzed by means of inferential statistics. The results highlight a widespread perception of climate change as a general threat for the environment, but not directly transposed to the frequency and intensity of future geohazards. Certainly, changes in temperatures and rainfall are widely expected and acknowledged, yet the comprehension related to the hydrogeological effects seems to vary proportionally to the physical proximity to these hazards. Such outcomes underline that there is still a common lack of understanding of the eventual local impact of the climate crisis. For these reasons, it is suggested that decision makers consider directing their efforts to enhance the citizens’ knowledge base in order to build a climate-resilient society.