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Los depósitos fósiles de Lana'i se formaron por múltiples eventos en lugar de un solo tsunami gigante
K H Rubin1, C H Fletcher, C Sherman
1Department of Geology and Geophysics, SOEST, University of Hawaii, Honolulu 96822, USA. krubin@soest.hawaii.edu
Nature
|December 29, 2000
Resumen
Los tsunamis gigantes no son responsables de los depósitos de grava de las islas hawaianas. En cambio, múltiples eventos de deposición durante largos períodos, impulsados por la actividad normal de las olas y las tormentas, formaron estas características.
Área de la Ciencia:
- Geología Geología Geología.
- Paleoclimatología Paleoclimatología
- Ciencias Marinas Ciencias Marinas.
Sus antecedentes:
- Anteriormente se pensaba que los deslizamientos de tierra submarinos en las islas hawaianas causaban tsunamis gigantes.
- Se planteó la hipótesis de que estos tsunamis depositarían grava caótica en lo alto de Lana'i y Moloka'i.
- El depósito de grava de Hulopoe en Lana'i ha sido un foco clave para esta hipótesis.
Objetivo del estudio:
- Para investigar la hipótesis de que los tsunamis gigantes causaron la deposición de la grava de las islas hawaianas.
- Para determinar el proceso de formación y el momento del depósito de grava Hulopoe en Lana'i.
- Reevaluar la hipótesis de la "ola gigante" para la deposición de grava costera.
Principales métodos:
- La datación del uranio-torio (U-Th) de los corales dentro de la grava de Hulopoe.
- Análisis de las relaciones estratigráficas, incluyendo cambios de fachadas y hiatos.
- Evaluación geográfica y estratigráfica de los grupos de edad de los corales dentro del depósito.
Principales resultados:
- La grava de Hulopoe contiene corales de dos grupos de edad distintos: las etapas de isótopos marinos 5e (hace unos 135.000 años) y 7 (hace unos 240.000 años).
- El depósito de grava muestra un ordenamiento geográfico y estratigráfico significativo, lo que indica múltiples eventos de deposición.
- Estos eventos fueron separados por períodos de tiempo considerables, lo que contradice un solo evento de tsunami gigante.
Conclusiones:
- La hipótesis de la "ola gigante" es invalidada por la evidencia de múltiples eventos de deposición separados en el tiempo.
- Es probable que las gravillas se hayan depositado durante los períodos interglaciales por procesos regulares de la costa hawaiana (ondas estacionales, tormentas, tsunamis normales).
- La altura actual de la grava de Hulopoe se atribuye a la elevación de Lana'i durante el tiempo geológico.
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