Upper air circulation and thermal anomalies over India and neighbourhood vis-à-vis Indian summer monsoon activity

The three dimensional circulation and thermal anomaly features associated with droughts and floods India are examined using 20 year of upper wind data over India and neighbourhood. The analysis reveals that years of droughts (floods) in India are associated with cyclonic (anticyclonic) circulation anomalies and cold (warm) thermal anomalies in the troposphere between 500 hPa and 200 hPa over northwestern India. In drought years (flood years) upper tropospheric westerly (easterly) anomalies are observed in the lower latitudes in the months of May and June. Tibetan anticyclone shifted to east of its normal position in drought years , during the month of June. The correlation coefficient between the meridional component of the wind at 200 hPa over northwestern India and the summer monsoon rainfall found to be -0.72 which is significant.

The Tharsis mantle source of depleted shergottites revealed by 90 million impact craters

The only martian rock samples on Earth are meteorites ejected from the surface of Mars by asteroid impacts. The locations and geological contexts of the launch sites are currently unknown. Determining the impact locations is essential to unravel the relations between the evolution of the martian interior and its surface. Here we adapt a Crater Detection Algorithm that compile a database of 90 million impact craters, allowing to determine the potential launch position of these meteorites through the observation of secondary crater fields. We show that Tooting and 09-000015 craters, both located in the Tharsis volcanic province, are the most likely source of the depleted shergottites ejected 1.1 million year ago. This implies that a major thermal anomaly deeply rooted in the mantle under Tharsis was active over most of the geological history of the planet, and has sampled a depleted mantle, that has retained until recently geochemical signatures of Mars’ early history.

The Carbon Dioxide Emission as Indicator of the Geothermal Heat Flow: Review of Local and Regional Applications with a Special Focus on Italy

We review the methods based on the measurement of CO2 emissions for the computation of geothermal heat flow, both at a local (hydrothermal sites, a few km2) and regional scale (hundreds km2). At the local scale, we present and discuss the cases of the Latera caldera and Torre Alfina (Italy) geothermal systems. At Torre Alfina and Latera, the convection process sustains a CO2 emission of ~1 kg s–1 and ~4 kg s–1, and heat flows of 46 MW and 130 MW, respectively. At the regional scale, we discuss the case of the central Apennine (Italy), where CO2 mass and enthalpy balances of regional aquifers highlights a wide and strong thermal anomaly in an area of low conductive heat flow. Notably, the CO2/heat ratios computed for the central Apennines are very similar to those of the nearby geothermal systems of Latium and Tuscany, suggesting a common source of CO2-rich fluids ascribed to the Tyrrhenian mantle.

Mt. Etna Paroxysms of February–April 2021 Monitored and Quantified through a Multi-Platform Satellite Observing System

On 16 February 2021, an eruptive paroxysm took place at Mt. Etna (Sicily, Italy), after continuous Strombolian activity recorded at summit craters, which intensified in December 2020. This was the first of 17 short, but violent, eruptive events occurring during February–April 2021, mostly at a time interval of about 2–3 days between each other. The paroxysms produced lava fountains (up to 1000 m high), huge tephra columns (up to 10–11 km above sea level), lava and pyroclastic flows, expanding 2–4 km towards East and South. The last event, which was characterised by about 3 days of almost continuous eruptive activity (30 March–1 April), generated the most lasting lava fountain (8–9 h). During some paroxysms, volcanic ash led to the temporary closure of the Vincenzo Bellini Catania International Airport. Heavy ash falls then affected the areas surrounding the volcano, in some cases reaching zones located hundreds of kilometres away from the eruptive vent. In this study, we investigate the Mt. Etna paroxysms mentioned above through a multi-platform satellite system. Results retrieved from Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Spinning Enhanced Visible and Infrared Imager (SEVIRI), starting from outputs of the Robust Satellite Techniques for Volcanoes (RSTVOLC), indicate that the 17th paroxysm (31 March–1 April) was the most powerful, with values of radiative power estimated around 14 GW. Moreover, by the analysis of SEVIRI data, we found that the 5th and 17th paroxysms were the most energetic. The Multispectral Instrument (MSI) and the Operational Land Imager (OLI), providing shortwave infrared (SWIR) data at 20/30 m spatial resolution, enabled an accurate localisation of active vents and the mapping of the areas inundated by lava flows. In addition, according to the Normalized Hotspot Indices (NHI) tool, the 1st and 3rd paroxysm (18 and 28 February) generated the largest thermal anomaly at Mt. Etna after June 2013, when Landsat-8 OLI data became available. Despite the impact of clouds/plumes, pixel saturation, and other factors (e.g., satellite viewing geometry) on thermal anomaly identification, the used multi-sensor approach allowed us to retrieve quantitative information about the 17 paroxysms occurring at Mt. Etna. This approach could support scientists in better interpreting changes in thermal activity, which could lead to future and more dangerous eruptions.

The late Paleozoic paired metamorphic belt of southern Central Chile: Consequence of a near-trench thermal anomaly?

The hypothesis of a subduction-related Miyashiro-type paired metamorphic belt for the origin of the late Paleozoic igneous and metamorphic complex in the Andean Coastal Cordillera has remained unquestioned since its proposal in the early seventies. A synthesis of the advances in the study of these metamorphic rocks between 33°S and 42°S, revising field relations among geological units, and geochemical and geochronological data from the contemporaneous granitoids of the Coastal Batholith, highlights inconsistencies in this model. The record of short-lived forearc magmatism in the late Paleozoic intruding the partially synchronous accretionary prism, and geochemical and isotopic data from the igneous rocks indicating sources from the accretionary prism sediments and the back-top lithosphere, suggest a departure from typical subduction settings. I conclude that the anomalous configuration of the paired metamorphic belt and the associated Coastal Batholith resulted from a complex geodynamic process involving a near-trench thermal anomaly caused by the subduction of a trench parallel mid-ocean ridge.

The impact of a tear in the subducted Indian plate on the Miocene geology of the Himalayan-Tibetan orogen

The Yadong-Gulu Rift, cutting across the Gangdese belt and Himalayan terranes, is currently associated with a thermal anomaly in the mantle and crustal melting at 15−20 km depth. The rift follows the trace of a tear in the underthrusted Indian continental lithospheric slab recognized by high resolution geophysical methods. The Miocene evolution of a 400-km-wide band following the trace of the tear and the rift, records differences interpreted as indicative of a higher heat flow than its surroundings. In the Gangdese belt, this band is characterized by high-Sr/Y granitic magmatism that lasted 5 m.y. longer than elsewhere and by the highest values of εHf(i) and association with the largest porphyry Cu-Mo deposits in the Gangdese belt. Anomalously young magmatic rocks continue south along the rift in the Tethyan and Higher Himalayas. Here, a 300-km-wide belt includes some of the youngest Miocene Himalayan leucogranites; the only occurrence of mantle-derived mafic enclaves in a leucogranite; young mantle-derived lamprophyre dikes; and the youngest and hottest migmatites in the Higher Himalayas. These migmatites record a history of rapid exhumation contemporaneous with the exhumation of Miocene mafic eclogite blocks, which are unique to this region and which were both heated to >800 °C at ca. 15−13 Ma, followed by isothermal decompression. We suggest that the prominent tear in the Indian lithosphere, sub-parallel to the rift, is the most likely source for these tectono-thermal anomalies since the Miocene.