Search results for "lake"
showing 10 items of 369 documents
Water level regulation in winter triggers fouling of fishing nets by the diatom Aulacoseira islandica in a boreal lake
2015
Water level regulation related to hydroelectric power production and flood prevention is an important hydro-morphological pressure on many watercourses around the world. Fouling of fishing nets in autumn during the open water period and in winter under the ice is a common phenomenon in large Finnish lakes where the water level is regulated. This fouling of fishing nets can sometimes be so extensive that fishing has to be stopped. Based on the practical experiences of fishermen, the main cause for the under-ice fouling has been proposed to be the winter draw-down of water causing low water level and stronger currents in lakes, but no conclusive relationship between fouling and water level re…
Insights on Hydrothermal‐Magmatic Interactions and Eruptive Processes at Poás Volcano (Costa Rica) From High‐Frequency Gas Monitoring and Drone Measu…
2019
Texto completo del documento Identification of unambiguous signals of volcanic unrest is crucial in hazard assessment. Processes leading to phreatic and phreatomagmatic eruptions remain poorly understood, inhibiting effective eruption forecasting. Our 5‐year gas record from Poás volcano, combined with geophysical data, reveals systematic behavior associated with hydrothermal‐magmatic eruptions. Three eruptive episodes are covered, each with distinct geochemical and geophysical characteristics. Periods with larger eruptions tend to be associated with stronger excursions in monitoring data, particularly in SO2/CO2 and SO2 flux. The explosive 2017 phreatomagmatic eruption was the largest erupt…
Shifts in plankton assemblages promoted by free water surface constructed wetlands and their implications in eutrophication remediation
2015
Abstract Two units of free water surface constructed wetlands (FWSCWs) were created in 2009 in a Mediterranean protected site, the Albufera de Valencia Natural Park, to treat eutrophic inflows to the Albufera de Valencia lagoon, the largest coastal lagoon in the Iberian Peninsula, affected by cultural eutrophication. Data of phytoplankton and zooplankton biomass and richness of the inflows and outflows corresponding to the first 3.5 years of operation of the system have been analyzed to evaluate the role of plankton in the eutrophication reversion. The FWSCWs significantly reduced the exported microalgal biomass, stimulated the potential mixotrophic groups of phytoplankton such as Euglenoph…
Volcanic Lakes in Africa: The VOLADA_Africa 2.0 Database, and Implications for Volcanic Hazard
2021
Volcanic lakes pose specific hazards inherent to the presence of water: phreatic and phreatomagmatic eruptions, lahars, limnic gas bursts and dispersion of brines in the hydrological network. Here we introduce the updated, interactive and open-access database for African volcanic lakes, country by country. The previous database VOLADA (VOlcanic LAke DAta Base, Rouwet et al., Journal of Volcanology and Geothermal Research, 2014, 272, 78–97) reported 96 volcanic lakes for Africa. This number is now revised and established at 220, converting VOLADA_Africa 2.0 in the most comprehensive resource for African volcanic lakes: 81 in Uganda, 37 in Kenya, 33 in Cameroon, 28 in Madagascar, 19 in Ethiop…
Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo
2017
Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variati…
Byers Peninsula: A reference site for coastal, terrestrial and limnetic ecosystem studies in maritime Antarctica
2009
Abstract This article describes the development of an international and multidisciplinary project funded by the Spanish Polar Programme on Byers Peninsula (Livingston Island, South Shetlands). The project adopted Byers Peninsula as an international reference site for coastal and terrestrial (including inland waters) research within the framework of the International Polar Year initiative. Over 30 scientists from 12 countries and 26 institutions participated in the field work, and many others participated in the processing of the samples. The main themes investigated were: Holocene changes in climate, using both lacustrine sediment cores and palaeo-nests of penguins; limnology of the lakes, …
Major and trace element geochemistry of neutral and acidic thermal springs at El Chichón volcano, Mexico
2008
Abstract Four groups of thermal springs with temperatures from 50 to 80 °C are located on the S–SW–W slopes of El Chichon volcano, a composite dome-tephra edifice, which exploded in 1982 with a 1 km wide, 160 m deep crater left. Very dynamic thermal activity inside the crater (variations in chemistry and migration of pools and fumaroles, drastic changes in the crater lake volume and chemistry) contrasts with the stable behavior of the flank hot springs during the time of observations (1974–2005). All known groups of hot springs are located on the contact of the basement and volcanic edifice, and only on the W–SW–S slopes of the volcano at almost same elevations 600–650 m asl and less than 3…
Ramification of lithic production and the search of small tools in Iberian Peninsula Middle Paleolithic
2015
The notion of recycling and it relationship with ramified productions and small tool production in Late Middle Paleolithic from the Iberian Peninsula are investigated. Results from Amalda, Axlor, Pen~a Miel, and Quebrada show that the production of small tools is one of the principal objectives of lithic provi- sioning in these sites. Whereas in Axlor and Amalda, this is achieved through the ramification of pro- duction, due to the remoteness of flint sources, in Quebrada, where raw material sources are closer, small flakes are obtained at the end of Levallois production. The implications for Neandertal society organi- zation of this small tool production is discussed, and its evolution is …
Ledājkušanas ūdeņu baseini Ziemeļlatvijas un Vidusgaujas zemienēs Vēlā Vislas leduslaikmeta beigu posmā
2014
Disertācijā aplūkoti ledājkušanas ūdeņu baseini, kuri eksistēja Ziemeļvidzemes un Vidusgaujas zemienēs vēlā Vislas leduslaikmeta deglaciācijas laikā. Pirmo reizi Latvijā iekšzemes ledājkušanas baseinu rekonstruēšanā ir ņemta vērā Zemes virsmas šķietamā pacelšanās, kā arī pašas rekonstrukcijas ir veiktas ĢIS vidē ar modelēšanas rīku palīdzību. Darbā ir veiktas Vidusgaujas, Smiltenes un Strenču ledāja sprostezeru rekonstrukcijas ūdens līmeņu kritumam no 125 līdz 46 m v.j.l., kuras parāda minēto sprostezeru izplatību, dziļumu, ūdens pieteces un noteces vietas, attīstību laikā un saistību ar citām tālaika ūdenstilpēm. Baseinus veidojošo un tiem sekojošo eolo procesu nogulumu datējumi ar OSL met…
Bóg i „śmierć Boga” w pisarstwie Tomasza Mertona
2018
Thomas Merton, the American Trappist monk and religious writer, is the author of The Seven Storey Mountain, Seeds of Contemplation, The Ascent to Truth, the New Man and many other works in the field of spirituality. He is also an analytical thinker comparing scholastic philosophy with modern existentialism. In Conjectures of a guilty bystander he takes up a polemic with the Heideggerian concept of death. Merton examines this issue from the point of view of Christian axiology. The dogma of existentialism is something illogical to him: the idea of “the death of God”. His entire work is linked to a polemic with Thomas Altizer, an Anglican theologian inspired by the philosophy of Fryderyk Nietz…