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| Titel |
Effects of 2010 Hurricane Earl amidst geologic evidence for greater overwash at Anegada, British Virgin Islands |
| VerfasserIn |
B. F. Atwater, Z. Fuentes, R. B. Halley, U. S. Ten Brink, M. P. Tuttle |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: Caribbean Waves 2 Conference ; Nr. 38 (2014-03-07), S.21-30 |
| Datensatznummer |
250121294
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| Publikation (Nr.) |
 copernicus.org/adgeo-38-21-2014.pdf |
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| Zusammenfassung |
A post-hurricane survey of a Caribbean island affords comparisons with
geologic evidence for greater overwash at the same place. This comparison,
though of limited application to other places, helps calibrate coastal
geology for assessment of earthquake and tsunami potential along the Antilles
Subduction Zone.
The surveyed island, Anegada, is 120 km south of the Puerto Rico Trench and
is near the paths of hurricanes Donna (1960) and Earl (2010), which were at
or near category 4 when at closest approach. The survey focused on Earl's
geologic effects, related them to the surge from Hurricane Donna, and
compared them further with erosional and depositional signs of southward
overwash from the Atlantic Ocean that dates to 1200–1450 AD and to
1650–1800 AD. The main finding is that the geologic effects of these
earlier events dwarf those of the recent hurricanes.
Hurricane Earl's geologic effects at Anegada, observed mainly in 2011, were
limited to wrack deposition along many of the island's shores and salt ponds,
accretion of small washover (spillover) fans on the south shore, and the
suspension and deposition of microbial material from interior salt ponds.
Earl's most widespread deposit at Anegada, the microbial detritus, was
abundantly juxtaposed with evidence for catastrophic overwash in prior
centuries. The microbial detritus formed an extensive coating up to 2 cm
thick that extended into breaches in beach-ridge plains of the island's north
shore, onto playas that are underlain by a sand-and-shell sheet that extends
as much as 1.5 km southward from the north shore, and among southward-strewn
limestone boulders pendant to outcrops as much as 1 km inland. Earl's
spillover fans also contrast with a sand-and-shell sheet, which was dated
previously to 1650–1800, by being limited to the island's south shore and by
extending inland a few tens of meters at most.
These findings complement those reported in this issue by Michaela Spiske and
Robert Halley (Spiske and Halley, 2014), who studied a coral-rubble ridge
that lines part of Anegada's north shore. Spiske and Halley attribute the
ridge to storms that were larger than Earl. But they contrast the ridge with
coral boulders that were scattered hundreds of meters inland by overwash in
1200–1450. |
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