The erosion of volcanic ocean islands creates dramatic landscapes, modulates Earth's carbon cycle, and delivers sediment to coasts and reefs. Despite concerns that modern sediment fluxes to island coasts may exceed long-term fluxes, little is known about how erosion rates and processes vary across island interiors. This study by Ken L. Ferrier and colleagues presents new measurements of erosion rates over five-year to five-million-year time scales on the Hawaiian island of Kauai, which is home to one of Earth's steepest precipitation gradients, with mean annual precipitation ranging from 0.5 to 9.5 m. Eroded rock volumes from basins across Kauai indicate that basin-averaged erosion rates over the past several million years vary by a factor of 40 across the island and increase with modern mean annual precipitation. In the Hanalei basin of Kauai, estimates of sediment fluxes and solute fluxes imply that modern erosion rates are no more than 2.3 plus or minus 0.6 times faster than erosion rates over the past few thousand years, as determined by new measurements of helium-3 in olivines in stream sediment. To the extent that modern precipitation patterns resemble long-term precipitation patterns, these measurements provide new support for a link between precipitation rates and long-term basin-averaged erosion rates.
Ken L. Ferrier et al., Dept. of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology,DOI: dx.doi.org/10.1130/B30726.1.