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The Macquarie Triple Junction is a geologically active tectonic boundary located at at which the Indo-Australian Plate, Pacific Plate, and Antarctic Plate collide and interact. The term Triple Junction is given to particular tectonic boundaries at which three separate tectonic plates meet at a specific, singular location. The Macquarie Triple Junction is located on the seafloor of the southern region of the Pacific Ocean, just south of New Zealand. This tectonic boundary was named in respect to the nearby Macquarie Island, which located southeast of New Zealand. == Evolution, stability, and migration == Our understanding of the evolution of the Macquarie Triple Junction was made possible due to extensive research of the regions tectonic magnetic anomalies as well as local fractures reconstruction. The origin of the Macquarie Triple Junction has been interpreted to have occurred 47.91 Mya (million years ago), based on Anomaly 21. Thorough reconstruction of the Macquarie Triple Junction begins at 33.3 Mya, in respect to Anomaly 13o, and can be simply described as a southeastward migration of approximately 1100 km in respect to the Australian Plate. The total migration was largely driven by the Australian–Pacific transform boundary. At 33.3 Mya, the Macquarie Triple Junction was a stable ridge–transform fault–transform fault triple junction. In reference to the Australian Plate, the triple junction moved southeast at an angle of 120° at an approximate rate of 40 km/million years.〔 This trajectory remain relatively constant throughout the Oligocene from 33.3 to 20.1 Mya. During this period of time the Australian-Pacific boundary underwent a transformation from mid-ocean ridge to a strike-slip fault and lastly at 20.1 Mya to a transpression convergent boundary.〔 Then 10.9 Mya, the Macquarie Triple Junction evolved into a ridge-trench-fault triple junction due to the alteration of the Australian–Pacific Boundary motion. This oblique convergent boundary instigated a clockwise rotation of the Macquarie Ridge Complex forming the Hjord Trench and numerous fracture zones around the Macquarie Ridge Complex.〔Lodolo, E. and F. Coren (1994). "The Westernmost Pacific Antarctic plate boundary in the vicinity of the Macquarie triple junction." (In C.A. Ricci, ed. Terra Antarctica, vol.1). pp. 158–161〕 This rotation also transpired into the Macquarie Triple Junction changing its migration path to an angle of 150° and rate of 34 km/million years in reference to the Australian Plate, making the migration direction southward. Between 5.9 and 2.6 Mya, the Macquarie Triple Junction evolved back into a Ridge–Transform Fault–Transform Fault triple junction as the convergence at the Hjort Trench diminished and Antarctic–Pacific spreading boundary changed back into a transform fault.〔 This is the current state of the Macquarie Triple Junction and is interpreted as a stable ridge–fault–fault triple junction. 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「Macquarie Triple Junction」の詳細全文を読む スポンサード リンク
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