|
Dominica's Boiling Lake is situated in the Morne Trois Pitons National Park - Dominica's World Heritage site. It is a flooded fumarole east of Roseau, Dominica. It is filled with bubbling greyish-blue water that is usually enveloped in a cloud of vapour. The lake is approximately to across. The first recorded sighting of the lake was in 1870 by Mr. Watt and Dr. Nicholls, two Englishmen working in Dominica at that time. In 1875, Mr. H. Prestoe, a government botanist, and Dr. Nicholls were commissioned to investigate this natural phenomenon. They measured the water temperature and found it to range from along the edges, but could not measure the temperature at the centre where the lake is actively boiling. They recorded the depth to be greater than . Periodically, there have been fluctuations in the level and activity of the lake. In the 1870s it was deep, after a phreatic eruption nearby, in 1880 the lake disappeared and formed a fountain of hot water and steam. Another phreatic eruption lowered the lake level by some from December 2004 to April 2005; later the lake level rose again, refilling the lake in just one day.〔Fournier et al. (2010) ''Boiling Lake of Dominica, West Indies: high-temperature volcanic crater lake dynamics'' Journal of Geophysical Research, vol. 114, B02203〕 The rapid draining and refilling of the lake implies that it is suspended above the local water table. A continuous flux of steam or gas generated by an underlying magmatic intrusion drives water up into the lake.〔 A disturbance to the supply of gas can cause the lake to drain through the porous connection that normally allows steam to rise and heat the lake 〔Witham et al. (2006) ''Stability of Lava Lakes'', Journal of Volcanology and Geothermal Research vol. 158 p321-332〕 There is no road leading directly to the lake. It is approximately a return hike to the lake from the nearest road. The hike can be divided into three parts that take about one hour each. Part I starts in Laudat, by Titou Gorge and ends at Breakfast River, where hikers can fill up with fresh water. Part II continues up Morne Nicholls which has an altitude of 3,168 feet, and ends at the top of the Valley of Desolation. Part III starts with a dangerous descent into the Valley of Desolation, followed by a long hike past sulfur springs and hot pools, until finally reaching a peak overlooking boiling lake. The lake rests at the bottom of a large sinkhole-like basin. More accurately, it is a flooded fumarole, an opening, crack or hole, in the Earth's crust, generally located within the vicinity of a volcano, which emits steam and gases escaping from molten lava below. Currently, the lake is viewable from a broad, cliff-top ledge about directly above its shore. High rock walls surround and create the basin. The lake's grayish-blue water is easily viewed in its perpetual rolling-boil state which looks like a giant pot of water cooking and steaming on a stove. The basin's water is replenished by rainfall and two small streams which drain into the area. The water then seeps down to the lava and is heated to the boiling point. The trail leads through another volcanic area called the Valley of Desolation. The air around the area is hot, steamy and moist, supported by the sharp, acrid smell of sulphur. The area is known to have been filled with vapors and gases that escapes bubbling and escaping from boiling sulphur-water pots, small spraying and hissing geysers, cracks and holes, and a small stream that runs through and beneath the terrain. Tiny invisible sprays of steam will easily burn an ankle or foot. On 6 July 2007, adventure-film maker George Kourounis became the first person to ever cross the boiling lake from above, suspended by ropes over the most violently boiling section. This event was filmed for the TV series ''Angry Planet''. Dominica's Boiling Lake is the second largest hot lake in the world. The largest is Frying Pan Lake, located in Waimangu Valley near Rotorua, New Zealand. ==See also== *Hot spring *List of hot springs 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Boiling Lake」の詳細全文を読む スポンサード リンク
|