Wednesday, May 12, 2010

Portugal - Azores - Caldeiras das Furnas

Caldeiras das Furnas or Fumaroles of Furnas in Furnas, a parish in the district of Povoação in the Azores.

The third of the four postcards sent by Antonio.

This is from Wikipedia : A fumarole (Latin fumus, smoke) is an opening in Earth's (or any other astronomical body's) crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The name solfatara, from the Italian solfo, sulfur (via the Sicilian dialect), is given to fumaroles that emit sulfurous gases.

Fumaroles may occur along tiny cracks or long fissures, in chaotic clusters or fields, and on the surfaces of lava flows and thick deposits of pyroclastic flows. A fumarole field is an area of thermal springs and gas vents where magma or hot igneous rocks at shallow depth are releasing gases or interacting with groundwater. From the perspective of groundwater, fumaroles could be described as a hot spring that boils off all its water before the water reaches the surface.

A good example of fumarole activity on Earth is the famous Valley of Ten Thousand Smokes, which was formed during the 1912 eruption of Novarupta in Alaska. Initially, there were thousands of fumaroles in the cooling ash from the eruption, but over time most of them have become extinct. Fumaroles may persist for decades or centuries if they are above a persistent heat source, or disappear within weeks to months if they occur atop a fresh volcanic deposit that quickly cools. There are also an estimated four thousand fumaroles within the boundaries of Yellowstone National Park. Around 2009, a fumarole opened up on Chair 3 at Mammoth Mountain Ski Resort in California. A mesh fence and warning sign was put around the hole to warn skiers of the danger.

Another example is an array of fumaroles in the Valley of Desolation in Morne Trois Pitons National Park in Dominica. Fumaroles emitting sulfurous vapors form surface deposits of sulfur-rich minerals, which are mined in:

* Indonesia at Kawah Ijen and Arjuno-Welirang
* Chile at Chajnantour near San Pedro de Atacama
* China at Xingyan in Sichuan province
* New Zealand at White Island in the Bay of Plenty (now defunct)

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