The Havre Trough (Havre Basin) is a currently actively rifting back-arc basin about 100 km (62 mi) to 120 km (75 mi) wide, between the Australian Plate and Kermadec microplate. The trough extends northward from New Zealand's offshore Taupō Volcanic Zone commencing at Zealandia's continental shelf margin and continuing as a tectonic feature, as the Lau Basin which currently contains active seafloor spreading centers. Its eastern margin is defined by the Kermadec Ridge created by Pacific Plate subduction under the Kermadec microplate, while the western margin is the remnant Lau-Colville Ridge.
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👉 Havre Trough in the context of Tonga-Kermadec Ridge
The Tonga–Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga–Kermadec island arc.It is a result of the most linear, fastest converging, and seismically active subduction boundary on Earth, the Kermadec–Tonga subduction zone, and consequently has the highest density of submarine volcanoes.
The Tonga–Kermadec Ridge stretches more than 3,000 km (1,900 mi) north-northeast from New Zealand's North Island. The Pacific Plate subducts westward beneath the Australian Plate along the ridge. It is divided into two segments, the northern Tonga Ridge and southern Kermadec Ridge, by the Louisville Seamount Chain. On its western side, the ridge is flanked by two back-arc basins, the Lau Basin and Havre Trough, that began opening at 6 Ma and 2 Ma respectively. Beyound the basins is the Lau-Colville Ridge. Together with these seafloor structures the ridge forms the eastward-migrating, 100 million year old Lau–Tonga–Havre–Kermadec arc/back-arc system or complex.
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Havre Trough in the context of Lau Basin
The Lau Basin is a back-arc basin (also addressed as "interarc basin") at the Australian-Pacific plate boundary. It is formed by the Pacific plate subducting under the Australian plate. The Tonga-Kermadec Ridge, a frontal arc, and the Lau-Colville Ridge, a remnant arc, sit to the eastern and western sides of the basin, respectively. The basin has a raised transition area to the south where it joins the Havre Trough.