Evolution of submarine terraces off Northern Moloka’i, HI

Abstract

Submarine terraces off Northern Moloka’i, HI, have been understudied. Terraces are vital to our understanding of sea-level changes and terrestrial alterations. One study aimed to identify terraces and evaluate their evolution, and found three continuous terrace tracts. Bathymetric data, sub-bottom profiles, and Shipek grab samples were collected in this region during a cruise in late February 2023 on the R.V. Thompson. The data were processed and analyzed. Sixteen benches were identified, with most being formed by wave action but others due to faulting. While the primary goal of the study was to estimate the ages of terraces using sea-level curves, only two terraces could be aged. These ages being around 12.1 kyr and 13.5 kyr which is similar in age to corals dated offshore of Lanai, Most of the identified benches were unexpectedly deep and could not be aged. Terraces deeper than 200 m are speculated to have been deepened either by mass wasting events that moved former terraces down-slope or by volcanic loading that drove the subsidence of wave-cut terraces.