Support for the Giant Wave Hypothesis: evidence from submerged terraces off Lanai,Hawaii |
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Authors: | Jody M Webster David A Clague Juan Carlos Braga |
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Institution: | (1) School of Earth Sciences, James Cook University, Townsville, QLD, 4811, Australia;(2) Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA;(3) Departamento de Estratigrafia y Paleontologia, Universidad de Granada, Granada, Spain |
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Abstract: | The origin of subaerial coral conglomerate deposits on the Hawaiian islands of Lanai and Molokai is controversial, primarily
because these deposits are difficult to interpret and the vertical motion of these islands is poorly constrained. Based on
bathymetry, dive observations, sedimentary and radiocarbon data from coralline algal dominated deposits from two submerged
terraces at −150 and −230 m off Lanai, Lanai has experienced relatively little vertical movement over the last 30 ka. Using
internally consistent age versus depth relationships, paleowater depths, and published sea level data, we estimate that Lanai
has experienced maximum rates of uplift of 0.1 m/kyr or subsidence of 0.4 m/kyr over this period. Our analysis of possible
uplift mechanisms, published geophysical, numerical modelling, and recent tide data suggests that this is also the maximum
uplift rate for the last several hundred thousand years. Taken together these data support the interpretation that coral conglomerates
at elevations higher than +35 m on Lanai are tsunami deposits with a minimum wave run up > 170 m, rather than shoreline deposits
formed during the last two interglacials, then uplifted to their present elevations. |
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Keywords: | Hawaii Lanai Submerged reef terraces Subaerial coral conglomerates Tsunami |
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