There is currently disagreement over the cause of volcanic activity on Ross Island. The traditional view is that the area is underlain by amantle plume which has given rise to volcanism and, in conjunction with a second plume thought to be underMarie Byrd Land on the mainland to the east, a system ofrifts known as theWest Antarctic Rift System. Support for a plume origin includespetrological,geochemical, andisotopic evidence for a deep-mantle source,[2][3] high heat flow in the area,[4] high volcanic output,[5] domal uplift,[6][7] andseismic anomalies in the upper mantle consistent with a plume approximately 250 to 300 km (160 to 190 mi) in diameter extending 200 km (120 mi) below the surface where it changes into a narrow column that extends at least a further 400 km (250 mi)[8][9] and according to some studies as deep as 1,000 km (620 mi).[10][11] The area lacks the time-progressive volcanism typically associated with mantle plumes. This has been explained by theAntarctic Plate being stationary since the lateCretaceous.
Other observations appear to be inconsistent with the plume model. Uplift in the region lacks the circular symmetry typically associated with mantle plumes. Rifting occurred mainly in the late Cretaceous, whereas uplift occurred mainly in the middleEocene, so uplift followed extension rather than preceding it as would be expected with a mantle plume. The volume ofmagmatism, when the long duration of volcanic activity is taken into account, appears lower than would be expected to result from a mantle plume. Seismic imaging does not show the circular symmetry expected for a mantle plume but indicates rather a linear, tectonic feature extending fromTasmania to the Ross Sea.[12][13][14]
Owing to these issues, some scientists have questioned the plume model and propose instead a shallow,tectonic mechanism. In this view, lithospheric extension and rifting during the late Cretaceous stretched thelithosphere, giving rise to partial melts. Though insufficient to break the surface, fertile, low-liquidus material was distributed throughout the lithosphericmantle. During the middle Eocene, tectonic changes in theSouthern Ocean gave rise to further lithospheric deformation, causing strike-slip faulting which enableddecompression melting andextrusion of the fertile material emplaced during the late Cretaceous.[12][13][14]
^abRochi, S.; Storti, F.; Di Vincenzo, G.; Rossetti, F. (2003). "Intraplate strike-slip tectonics as an alternative to mantle plume activity for the Cenozoic rift magmatism in the Ross Sea region, Antarctica". In Storti, F; Holdsworth, R.E.; Salvini, F. (eds.).Intraplate strike-slip deformation belts: Geological Society, London, Special Publications, 210. Vol. 210. Geological Society of London. pp. 145–158.doi:10.1144/GSL.SP.2003.210.01.09.S2CID134316807.{{cite book}}:|journal= ignored (help)
^abRocchi, S.; Armienti, P.; Di Vincenzo, G. (2005). "No plume, no rift magmatism in the West Antarctic Rift". In Foulger, G.R.; Natland, J.H.; Presnall, D.C.; Anderson, D.L. (eds.).Plates, plumes and paradigms: Geological Society of America Special Paper 388. Geological Society of America. pp. 435–447.doi:10.1130/0-8137-2388-4.435.ISBN9780813723884.
