|
Piton de la Fournaise (French): "Peak of the Furnace" is a shield volcano on the eastern side of Réunion island (a French department) in the Indian Ocean. It is currently one of the most active volcanoes in the world, along with Kīlauea in the Hawaiian Islands (Pacific Ocean), Stromboli, Etna (Italy) and Mount Erebus in Antarctica. A previous eruption began in August 2006 and ended in January 2007. The volcano erupted again in February 2007, on 21 September 2008 and on 9 December 2010, which lasted for two days. The most recent eruption began on 1 August 2015. The volcano is located within Réunion National Park, a World Heritage site. Piton de la Fournaise is often known locally as ''le Volcan'' (The Volcano); it is a major tourist attraction on Réunion island. ==Geography== The top part of the volcano is occupied by the Enclos Fouqué, a caldera wide. High cliffs known as ''remparts'' form the caldera's rim. The caldera is breached to the southeast into the sea. It is unstable and is in the initial stages of failure. It will eventually collapse into the Indian Ocean. Whether it will generate a so-called "megatsunami" is controversial. There is evidence on the submerged flanks and abyssal plain of earlier failures. The lower slopes are known as the ''Grand Brûlé'' ("Great Burnt"). Most volcanic eruptions are confined to the caldera. Inside the caldera is a 400 meter high lava shield known as Dolomieu. Atop the lava shield are Bory Crater (''Cratère Bory'') and Dolomieu Crater (''Cratère Dolomieu''), named for French geologist Déodat Gratet de Dolomieu, which is by far the wider of the two. Many craters and spatter cones can be found inside the caldera and the outer flanks of the volcano. At the beginning of the path that leads to the summit, there lies a noticeable small crater known as Formica Leo, named for its similar shape to the pitfall built by the antlion. Some of the beaches there are of a greenish colour, because of the olivine sand resulting from picrite basalt lavas. The ''Grand Brûlé'' is formed from solidified lava flows accumulated over hundreds of thousands of years; the most recent ones are often the darkest and most vegetation-free, while older ones can be covered by dense wild vegetation. Iridium is being ejected through these vents. This volcano is over 530,000 years old, and for most of its history, its flows have intermingled with those from Piton des Neiges, a larger, older and heavily eroded extinct volcano which forms the northwest two-thirds of Réunion Island. There were three episodes of caldera collapses 250,000, 65,000 and 5,000 years ago. The volcano was formed by the Réunion hotspot, which is believed to have been active for the past 66 million years. There is evidence for explosive eruptions in the past. One explosive eruption about 4,700 years ago may have had a VEI (Volcanic Explosivity Index) of 5, which is the same as the 18 May 1980 eruption of Mount St. Helens. 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「Piton de la Fournaise」の詳細全文を読む スポンサード リンク
|