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Landslides and the evolution of El Hierro in the Canary Islands

Landslides and the evolution of El Hierro in the Canary Islands
Landslides and the evolution of El Hierro in the Canary Islands
Seismic and sonar data have been used to evaluate the extent and characteristics of giant landslides on the flanks of El Hierro in the Canary Islands. As the youngest and most southwesterly of the Canary Islands, El Hierro has experienced rapid growth and destructive events in its 1.12 million year history. At least four giant landslides (El Golfo, El Julan, San Andres, and Las Playas) have modified ~450 km3 of El Hierro during the last 200–300 thousand years, with each landslide event removing around 3% of the total edifice volume. The extent of landsliding indicates that it is the main process of decay. We characterise flank morphology around El Hierro and distinguish between rugged, unfailed flank, failed flank and steep gullied ridge. Flanks affected by landsliding have downslope long profiles with distinctive b coefficients and exponential forms. The El Golfo landslide is the most recent (15 ka), best described and clearly defined landslide in the Canary Islands. The El Julan landslide (SW flank) has an estimated volume of 130 km3, an age of >200 ka and is characterised by gravitational slumping. On the SE flank, two new landslide events are reported. The younger landslide (Las Playas) occurred 145–176 ka, has a narrow, steep-sided embayment and a corresponding blocky debris avalanche deposit. The older landslide (San Andres) is recognised on the basis of a highly chaotic seismic facies offshore and reduced upper flank gradients. Its lack of an upper flank embayment and offshore blocky debris avalanche lead us to interpret that the landslide involved gravitational slumping, possibly a series of events, which reduced upper flank gradients, but did not catastrophically collapse to produce a debris avalanche.
SLUMPING, SUBMARINE LANDSLIDES, CANARY ISLAND WATERS, OCEAN ISLANDS, GEOLOGY
0025-3227
271-293
Gee, M.J.R.
340d46be-e8cf-4829-9012-87f0902a2eb1
Watts, A.B.
6c5f361f-d238-4226-8312-c0eb48ccecc5
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Mitchell, N.C.
0d8f263f-11a2-49a7-ac49-b65918ad1b23
Gee, M.J.R.
340d46be-e8cf-4829-9012-87f0902a2eb1
Watts, A.B.
6c5f361f-d238-4226-8312-c0eb48ccecc5
Masson, D.G.
edd44c8b-38ca-45fb-8d0d-ac8365748a45
Mitchell, N.C.
0d8f263f-11a2-49a7-ac49-b65918ad1b23

Gee, M.J.R., Watts, A.B., Masson, D.G. and Mitchell, N.C. (2001) Landslides and the evolution of El Hierro in the Canary Islands. Marine Geology, 177 (3/4), 271-293. (doi:10.1016/S0025-3227(01)00153-0).

Record type: Article

Abstract

Seismic and sonar data have been used to evaluate the extent and characteristics of giant landslides on the flanks of El Hierro in the Canary Islands. As the youngest and most southwesterly of the Canary Islands, El Hierro has experienced rapid growth and destructive events in its 1.12 million year history. At least four giant landslides (El Golfo, El Julan, San Andres, and Las Playas) have modified ~450 km3 of El Hierro during the last 200–300 thousand years, with each landslide event removing around 3% of the total edifice volume. The extent of landsliding indicates that it is the main process of decay. We characterise flank morphology around El Hierro and distinguish between rugged, unfailed flank, failed flank and steep gullied ridge. Flanks affected by landsliding have downslope long profiles with distinctive b coefficients and exponential forms. The El Golfo landslide is the most recent (15 ka), best described and clearly defined landslide in the Canary Islands. The El Julan landslide (SW flank) has an estimated volume of 130 km3, an age of >200 ka and is characterised by gravitational slumping. On the SE flank, two new landslide events are reported. The younger landslide (Las Playas) occurred 145–176 ka, has a narrow, steep-sided embayment and a corresponding blocky debris avalanche deposit. The older landslide (San Andres) is recognised on the basis of a highly chaotic seismic facies offshore and reduced upper flank gradients. Its lack of an upper flank embayment and offshore blocky debris avalanche lead us to interpret that the landslide involved gravitational slumping, possibly a series of events, which reduced upper flank gradients, but did not catastrophically collapse to produce a debris avalanche.

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Published date: 2001
Keywords: SLUMPING, SUBMARINE LANDSLIDES, CANARY ISLAND WATERS, OCEAN ISLANDS, GEOLOGY

Identifiers

Local EPrints ID: 7934
URI: http://eprints.soton.ac.uk/id/eprint/7934
ISSN: 0025-3227
PURE UUID: f9c270bd-5519-442e-9c5c-2226586d8790

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Date deposited: 10 Aug 2004
Last modified: 15 Mar 2024 04:49

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Author: M.J.R. Gee
Author: A.B. Watts
Author: D.G. Masson
Author: N.C. Mitchell

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