Physico-chemical and biological aspects of Lake Albano
Lake Albano is deep and has a small surface area, which reduces the potential for mixing across its full depth. This can lead to dangerous accumulations of carbon dioxide in the bottom waters of the lake deriving from subterranean magmatic processes. It has been proposed that limnic gas eruptions emanating from these deep waters represent the most significant present-day natural hazard of the Colli Albani volcano. Although recent evidence has shown that the lake is not meromictic and that rare full mixing events do occur, reducing to some extent the risk of limnic eruptions. At present the lake volume and water quality is rapidly decreasing due to over-abstraction and uncontrolled inputs of waste and sewage. These conditions may be responsible for large growths of toxic cyanobacteria in the lake. Lake water concentrations of microcystins (a cyanobacterial toxin) are well above the recommended limits set for drinking water, and some trace groundwater contamination has also been determined. These toxins can cause the death of animals and pose a significant risk to human health, representing a secondary hazard of the lake.
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The Colli Albani Volcano
The Colli Albani volcano (also Alban Hills volcano) is the large quiescent volcanic field that dominates the Roman skyline. The Colli Albani is one of the most explosive mafic calderas in the world, associated with intermediate to large volume ignimbrites. At present it shows signs of unrest, including periodic seismic swarms, ground uplift and intense diffuse degassing, which are the main short-term hazards. New studies have discovered deposits related to previously unknown pre-Holocene and Holocene volcanic and phreatic activity. In the fourth Century B.C.E. Roman engineers excavated a tunnel through the Albano maar crater wall to keep the lake from breaching the rim and flooding the surrounding countryside, events that had previously destroyed this region several times.
The Colli Albani Volcano contains 21 scientific contributions on stratigraphy, volcanotectonics, geochronology, petrography and geochemistry, hydrogeology, volcanic hazards, geophysics and archaeology, and a new 1:50 000 scale geological map of the volcano. The proximity to Rome and the interconnection between volcanic and human history also make this volcano of interest for both specialists and non-specialists.