|
The Faroe Islands lie on the Eurasian plate between Scotland, Norway and Iceland. The islands are of volcanic origin and are constructed of three layers of basalt, with the top and bottom layers resembling each other. The age of the islands is considered to be between 54 and 58 million years old, with the oldest material at the bottom.〔(Faroese Faculty of Science ) (in Faroese)〕 The Faroe Islands were built during a period of a few million years, some 55 million years ago in early Paleogene times, when Europe and Greenland started to separate, opening up what became the Northeast Atlantic Ocean. Countless numbers of volcanic eruptions built up a huge basalt plateau that covered almost the entire Faroe-Rockall region, together with the southeastern part of Greenland. In simple terms, each basalt lava flow of today’s Faroe Islands represents one volcanic eruption during that time period. Some volcanic eruptions produced voluminous sheet flows each with a thickness of several tens of meters and covering hundreds of square kilometres. Others built up compound lava flows each composed of several thin basalt layers. Some eruptions were violent and produced large volumes of volcanic ash that can be found in between the lava flows. Other strata between the basalt layers contain volcaniclastic and other sediments that bear witness of long time periods in between each of the eruptive events, with rich vegetation in a sub-tropic climate, and with local erosion or deposition of sediments in rivers and shallow lakes. One volcanically silent time period was especially long and resulted in the deposition of several sedimentary layers of various composition, including strata rich in organic material that subsequently have generated considerable volumes of coal. In recent times the coal has been worked from mines in between the basalt flows near the northern villages of Suðuroy. With the plate tectonic evolution, the Faroe Islands have slowly moved away from the active volcanic region, which today is concentrated in Iceland and along the Mid-Atlantic Ridge. Meanwhile, the Faroe-Rockall Plateau has by and large subsided beneath sea level while erosive forces – especially during the last few million years of alternating glacial and interglacial periods – have sculpted the landscape to their present-day shape. The overall thickness of volcanic and intervening rock layers of the Faroe Islands is more than 6 km, of which only 900m is located above the present sea level. The remaining part has been drilled in a 3½ km deep well in Lopra, Suðuroy. ==Notes== 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「Geology of the Faroe Islands」の詳細全文を読む スポンサード リンク
|