The ancient shorelines of Lanai, Hawaii, revisited

Support for the Giant Wave Hypothesis: evidence from submerged terraces off Lanai, Hawaii

“…Rubin et al (2000) estimated uplift rates of 0.15-0.29 m/kyr, based on the maximum elevations (23 and 59 m, respectively) of the dated MIS5e and MIS7 deposits, paleo-sea levels, and depositional depths. Subsequently, Keating and Helsley (2002) relocated the deposits at +170 and +190 m in Kaluakapo crater, close to those dated by Moore and Moore (1988), and interpreted them as shoreline features, thereby requiring minimum uplift rates of 1.2-1.4 m/kyr using the Moore and Moore (1988) 134 ka age for the +155 m deposits.…”

“…1) relative to the radial distance from Mauna Kea on the Hawaii (bathymetry data from Webster et al 2006) implied by Moore and Moore (1988) and Keating and Helsley (2002), based on the interpretation of the coral conglomerate deposits on Lanai as MIS5e and MIS7 shoreline features. Furthermore, our maximum subsidence rate of 0.4 m/kyr is significantly lower than Campbell's (1986) estimated 1.9 m/kyr rate based on correlation with the submerged Hawaiian terraces.…”

“…Subsequent workers (Grigg and Jones 1997;Rubin et al 2000;Keating and Helsley 2002;Felton et al 2006) presented sedimentologic and radiometric data Webster et al 2006). Recent ROV Tiburon sampling dives (black stars) and subaerial coral conglomerate deposits (black rectangles) on Molokai and Lanai are also shown and interpreted the deposits as shoreline features formed during previous highstands (MIS5e and MIS7), and at their present elevation due to uplift.…”

“…An argument against the Giant Wave Hypothesis (but for the uplift of Lanai) has been the size of the tsunami runup required to entrain coral material to a height of +326 m. Based on model calculations (Johnson and Mader 1994), Grigg and Jones (1997) argued that a tsunami striking Lanai triggered by the Lanai slump or the Alika phase 2 slide would not have been large enough to produce deposits at elevations > +180 m. This is roughly the maximum elevation of any of the deposits described by Moore (1984, 1988), or Keating and Helsley (2002), since no one has relocated the deposits from +326 m (Stearns 1966(Stearns , 1978 Given the limited extent and poor preservation of the coral conglomerates deposits and the differing interpretations of their sedimentologic features, we use a different approach that focuses on the submerged terrace deposits around Lanai.…”

“…These deposits were first interpreted as highstand deposits (Stearns 1966(Stearns , 1978, then mega-tsunami deposits (Giant Wave Hypothesis) Moore 1984, 1988;Moore 2000), then re-interpreted as highstand shoreline features deposited during the last two interglacials (Grigg and Jones 1997;Rubin et al 2000;Keating and Helsley 2002;Felton et al 2006). These different origins of the coral conglomerates (Giant Wave Hypothesis or uplifted shorelines) imply very different vertical histories for Lanai, a difference so large that even broad constraints on the vertical motion can distinguish between the two models.…”