Christmas Island Seamount Province
|Christmas Island Seamount Province|
|Height||up to 4,500 m (14,800 ft)|
|Volcanic arc/chain||Hotspot volcanoes|
|Age of rock||47 to 136 million years old|
The Christmas Island Seamount Province (also known as the Christmas Island Seamounts) is an unusual seamount (submarine volcano) formation named for Christmas Island, an Australian territory and wildlife reserve that is also part of the chain. The province consists of more than 50 seamounts, up to 4,500 m (14,800 ft) in height, within a 1,080,000 km2 (417,000 sq mi) area.
Unlike most seamount groups, the Christmas Island seamount formation does not form a long hotspot-based chain of increasingly older volcanoes, instead being a scattered grouping of volcanoes within a large radius. The origins of the formation have long been enigmatic for scientists; the Christmas Island area does not exhibit the hotspot chain formation that most seamount groups have, nor does it run perpendicular to a local rift zone, instead lying roughly parallel to the edge of the Australian Plate. Many of the seamounts are flat-topped guyots, showing that at one point the province was likely a group of active volcanic islands, before it was slowly eroded to its current subsurface level.
A study, published in 2011 and led by Kaj Hoernle of the University of Kiel in Germany, acquired and tested rock samples for 40Ar/39Ar, strontium, neodymium, hafnium and lead to determine its age and basis. The study found that the seamounts' rock was more similar to continental than oceanic crust, particularly resembling northwest Australian crust. The seamounts were found to be 47 to 136 million years old, decreasing in age from east to west, and at most 25 million years younger than the crust surrounding them. Plate reconstructions based on these dates showed that the seamounts formed where West Burma separated from Australia and India, during the breakup of Gondwana, approximately 150 million years ago. Hoernle and his associates proposed that the seamounts are made of recycled, delaminated continental crust enriched in mantle that was rising beneath the mid-ocean ridge forming at the time, and that this may be a relatively common process in shallow-basin areas.
- Crystal Gammon (20 December 2011). "Surprising Christmas Island Seamounts Mystery Solved". LiveScience through Yahoo News. Retrieved 30 December 2011.
- K. Hoernle, F. Hauff, R. Werner, P. van den Bogaard, A. D. Gibbons, S. Conrad, and R. D. Müller (27 November 2011). "Origin of Indian Ocean Seamount Province by shallow recycling of continental lithosphere". Nature Geoscience (Nature Publishing Group) 4: 883–887. Bibcode:2011NatGe...4..883H. doi:10.1038/ngeo1331. Retrieved 30 December 2011.
- K. Hoernle; F. Hauff; R. Werner; P. Van Den Bogaard; S. Conrad; A. Gibbons; D. Muller (2009). "The Christmas Island Seamount Province, Indian Ocean: Origin of intraplate volcanism by shallow recycling of continental lithosphere?" (PDF). Goldschmidt Conference Abstracts.