Morphometric interpretation of the northwest and southeast slopes of Tenerife, Canary Islands | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Morphometric interpretation of the northwest and southeast slopes of Tenerife, Canary Islands

Publication Type:

Journal Article

Source:

{JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH}, Volume {102}, Number {B9}, p.{20325-20342} (0)

Abstract:

{Both the northwest and southeast slopes of Tenerife, Canary Islands, owe their morphology to catastrophic sediment failures. An area of 4100 km(2) and a volume of about 2362 km(3) were involved in the failure. A 100- to 600-m-high scarp on the upper slope separates the sediment failures in the Orotova and Iced de los Vines Valleys on the northwest coast from those on the slope. A similar (700 m high) scarp also separates the failures on the southeast slope from the failure in Guimar Valley on land. The sediment failure off Las Bandas Del Sur volcanic fan does not have any land counterparts and was the result of the failure of the front (1700 m high) of this depocenter; two generations of debris flows are mappable off this depocenter. We infer that the slopes off Orotova, Iced, and Guimar represent the front of the debris avalanche and/or creep deposits that were created during the formation of the valleys. Downslope from the debris avalanche fronts are irregular surfaced masses extending to the base of the slope. The front may define the contact between the more dense deposits onshore and upper slope and the more fluid deposits on the lower slope, Incised on the debris avalanche on the northwest lower slope are three channeled debris flows grading seaward into turbidites. Only one of these channels occurs on the southeast slope. The breakaway surface of these sediment failures was the front of the debris avalanches and/or creep. We ascribe the failure of this front mainly to its rapid buildup, although groundwater sapping also may have contributed to its failure. On the southeast slope, movement along the northeast trending fault between Gran Canaria and Tenerife also may have been a contributing factor to the failure of the front. The debris flow deposits triggered by the failure of the sediment front on the northwest slope are characterized by ridges formed either by pressure between flows moving at different velocities or by scouring; at least one volcanic edifice occurs within the deposit. Although the avalanche and associated debris flow surfaces on the northwest slope appear pristine, being only partially covered by lava flow from a volcano in one of the channels, those on the southeast slope are partially buried by postfailure volcanics and detrital sediments. At the distal end of the slope failure masses, there are extensive fans, On the southeast slope these depocenters were reworked into a sediment drift field of northeast trending ridges by the southerly flowing North Atlantic Deep Water. On the surfaces of the fans off the northwest slope, there are exotic blocks transported downslope from their original positions either by riding on the surface of the highly dense debris avalanche or by being transported within the avalanche itself.}