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Lau Basin
The Lau Basin is a back-arc basin (also addressed as “interarc basin” 〔Karig, D. E., 1970a, Ridges and basins of the Tonga-Kermadec island arc system: Jour. Geophys. Research, v. 75, p. 239-254.
〕) 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 on the western and eastern sides of the basin respectively.〔Gill, J. B. 1976. "Composition and Age of Lau Basin and Ridge Volcanic Rocks: Implications for Evolution of an Interarc Basin and Remnant Arc." Bulletin of the Geological Society of America 87 (10): 1384-1395.〕
==History==
Lau Basin is a young basin (<= 5 m.y. old) 〔 that separates a previously continuous island arc by tensional rifting.〔
During the Pliocene, the Pacific plate was subducting beneath Australian plate.〔 The slab of the Pacific plate melted as it was thrust down, and then rose to form the original Tonga-Kermadec Ridge. Around 25 Ma B.P, the Pacific plate started to drift away from the Australian plate, thus splitting the volcanic ridge. The rifting was initially caused by extension until 6 Ma B.P, by which time seafloor spreading started in this region and eventually formed the Lau Basin between the separated ridges.〔Crawford, W. C., J. A. Hildebrand, L. M. Dorman, S. C. Webb, and D. A. Wiens. 2003. "Tonga Ridge and Lau Basin Crustal Structure from Seismic Refraction Data." Journal of Geophysical Research B: Solid Earth 108 (4): EPM 6-1 - 6- 17〕
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