Offshore continuation of volcanic rift zones, El Hierro, Canary Islands

Gee, M.J.R.; Masson, D.G.; Watts, A.B.; Mitchell, N.C.. 2001 Offshore continuation of volcanic rift zones, El Hierro, Canary Islands. Journal of Volcanology and Geothermal Research, 105 (1/2). 107-119.

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El Hierro is the youngest and most southwesterly of the seven Canary islands. The established view, based on subaerial geology, is that El Hierro is a classic example of an oceanic island with 120° –– spaced volcanic rift arms (VRZs) forming a "mercedes star". However, new offshore data do not support this simple interpretation. Instead of the discrete ridges of VRZs, we observe (to the NW and NE) broad areas of irregular morphology, which suggest that rifting activity might not be confined to narrow zones. Furthermore, our data suggest that the anomalously long and steep-flanked Southern Ridge could be part of an older, eroded volcanic edifice that predates much of the other submarine flanks of El Hierro. The Southern Ridge has a distinctive gullied morphology, which strongly contrasts with adjacent flanks. There is also a ~400-m-deep saddle in its longitudinal profile 15 km from the coastline, which we interpret as evidence that the Southern Ridge did not form by continuous dyke intrusion from the El Hierro volcanic centre. South of the saddle, mean flank slopes are 10° steeper (~30°) with a sharp slope break at 3700 m between the ridge and smoothly sedimented seafloor. These steeper slopes and lack of landslide scars to the south of the saddle indicate that the Southern Ridge is a stable edifice, relative to the rest of El Hierro. Surrounding sediments to the southeast appear to onlap the Southern Ridge. A large landslide deposit, El Julan (estimated age >200 ka), occurs to the west of the ridge. This landslide appears to have been constrained from spreading southeastwards by the Southern Ridge, resulting in an elevation difference of 300 m for the seafloor on either side of the ridge.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Additional Keywords: Canary Islands; El Hierro; flank rift zones; Southern Ridge .
Date made live: 23 Apr 2004 +0 (UTC)

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