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Frying Pan Lake (renamed Waimangu Cauldron in 1963 though not widely used) is the largest hot spring in the world. It is located in the Echo Crater of the Waimangu Volcanic Rift Valley, New Zealand and its acidic water maintains a temperature of .〔 Echo Crater was formed as part of the 1886 Mount Tarawera eruption, which opened several craters along a rift stretching southwest from Mount Tarawera to the nearby Southern Crater. After this event, the crater's floor partly filled with rainwater and heated groundwater, but it was not until after a large eruption in Echo Crater on 1 April 1917, that the resulting larger crater filled up from hot springs to reach its current size by mid 1918.〔(【引用サイトリンク】title=Waimangu: Geology )〕 The most recent eruption in Echo Crater occurred on 22 February 1973, destroying the Trinity Terrace area on the south-eastern shore of Frying Pan Lake. An area of colourful sinter terraces is still visible on the western shore of the lake. To the north, the lake is bounded by the steaming Cathedral Rocks. This monolithic rock structure is composed of at-least-60,000-year-old rhyolitic lava and was named Gibraltar Rock until the 1917 Echo Crater eruption completely changed its shape. A fumarole known as the Devil's Blowhole in the northern wall of Echo Crater also disappeared in that event.〔Information panel "Echo Crater" at lookout over Echo Crater〕 The water of Frying Pan Lake is typically steaming and can appear to be boiling due to carbon dioxide and hydrogen sulphide gas bubbling to the surface, however, the lake's average temperature is .〔Waimangu Wanderer Guide, April 2014〕 The lake and its outflow, Waimangu Stream (referred to as Hot Water Creek in the Waimangu Wanderer Guide), have an average pH level of 3.8, even though some of the boiling hot springs and vents on the lake's bed feed it with alkaline water of pH 8.2 to 8.7. This leads to various gradients of pH levels, which govern which types of algae are present, the blue-green algae Mastigocladus laminosus, or the eukaryotic algae Cyanidium caldarium.〔 The unique cyclic nature of the hydrothermal system interconnecting Frying Pan Lake and the nearby Inferno Crater Lake has been the subject of studies since monitoring equipment was installed in 1970 at the outflow stream from Frying Pan Lake and at Inferno Crater Lake.〔Information panel "Waimangu Monitoring Station" at the outflow from Frying Pan Lake, GNS Science and Waikato Regional Council〕 Both lakes' water levels and overflow volumes follow a complicated rhythm that repeats itself roughly every 38 days. When the water level and temperature of Inferno Crater Lake increase, the water level and outflow of Frying Pan Lake decrease. The outflow volume of Frying Pan Lake has decreased from over in 1970 to around , but varies by up to as part of the 38-day cycle.〔 Frying Pan Lake is one of the first major attractions encountered along the wheelchair-friendly main Waimangu walking track. The site of the extinct Waimangu Geyser is located not far from its north-eastern shore. ==References== 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「Frying Pan Lake」の詳細全文を読む スポンサード リンク
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