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L'évolution des formes et de la morphodynamique en domaine littoral volcanique : recherches dans l'archipel d'Hawaï

Guillaume Marie 1
1 LETG - Brest - Littoral, Environnement, Télédétection, Géomatique
LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554
Abstract : Various cycles connected with changes in the processes of erosion were identified in the evolution of volcanic coasts of the Hawaiian Archipelago. The growth of a lava delta depends on the extension of the fragments foundation formed during hydromagmatic reactions, which is itself linked with underwater topography. Collapse of the delta during a landslide in the basement generates a brutal retreat of the cliff of several tens of meters and significant risks for the walkers, when the form is being built and during its first year of inactivity. The fast stabilization of the underlying debris in only a few years strongly decreases the cliff retreat which is from now on triggered by marine agents and gravity, especially during rock slides and rock topples, the occurrence of which is decreasing.

The retreat by genesis of sea caves and sea arches is also current, producing an initial irregularization of the coastline before its grading. The formation of terraces by lateral quarrying leads to a stair shape platform, generally in the areas sheltered from the swells. Partly structural high tide shore benches can also be shaped, but they are quickly submerged by the rise of the related sea-level due to the volcano-isostasic subsidence. In the long-term, rock slides and rock slumps become more frequent on higher and older cliffs.

Microforms also develop on these coasts which have undergone a longer evolution. When the conditions are favorable, alveolar forms can nevertheless be quickly formed, particulary when the more resistant microlitic or hyaline texture of the surface crust allows an overhang. The processes of weathering seem to be confined in the rock discontinuities. Their different effectiveness according to the duration of emergence, particulary for salt weathering, shapes platforms with an external rampart, sprung from eustatic benches.
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Submitted on : Tuesday, September 13, 2005 - 3:44:30 PM
Last modification on : Wednesday, October 14, 2020 - 3:52:09 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:48:02 PM

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  • HAL Id : tel-00010123, version 1

Citation

Guillaume Marie. L'évolution des formes et de la morphodynamique en domaine littoral volcanique : recherches dans l'archipel d'Hawaï. Géographie. Université de Bretagne occidentale - Brest, 2004. Français. ⟨tel-00010123⟩

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