|
The Oruanui eruption of New Zealand's Taupo Volcano, the world's largest known eruption in the past 70,000 years, had a Volcanic Explosivity Index of 8. It occurred around 26,500 years ago in the Late Pleistocene and generated approximately of pyroclastic fall deposits, of pyroclastic density current (PDC) deposits (mostly ignimbrite) and of primary intracaldera material, equivalent to of magma. The eruption is divided into 10 different phases on the basis of nine mappable fall units and a tenth, poorly preserved but volumetrically dominant fall unit.〔Richard Smith, David J. Lowe and Ian Wright. '(Volcanoes - Lake Taupo )', ''Te Ara - the Encyclopedia of New Zealand'', updated 16-Apr-2007.〕 Modern Lake Taupo partly fills the caldera generated during this eruption; a structural collapse area is concealed beneath the lake, while the lake outline reflects coeval peripheral and volcano-tectonic collapse. Early eruption phases saw shifting vent positions; development of the caldera to its maximum extent (indicated by lithic lag breccias) occurred during phase 10. The Oruanui eruption shows many unusual features: its episodic nature, wide range of depositional conditions in fall deposits of very wide dispersal, and complex interplay of falls and pyroclastic flows. Tephra from the eruption covered much of the central North Island with ignimbrite up to deep. Ashfall affected most of New Zealand, with even an ash layer deposited on the Chatham Islands, away. Later erosion and sedimentation had long-lasting effects on the landscape, and caused the Waikato River to shift from the Hauraki Plains to its current course through the Waikato to the Tasman Sea. == See also == * North Island Volcanic Plateau * Hatepe eruption (Taupo Volcano, circa AD 180) 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「Oruanui eruption」の詳細全文を読む スポンサード リンク
|