Megatsunami deposits on Kohala volcano, Hawaii, from flank collapse of Mauna Loa.

The origin of coastal and high-elevation marine gravels on the Hawaiian islands of Lanai and Molokai is controversial, because the vertical tectonics of these islands is poorly constrained. The gravels are either from eustatic highstands or were left by massive tsunamis from offshore giant landslides. In contrast, at Kohala on the island of Hawaii, where continuous subsidence is well estab- lished, lithofacies analysis and dating of a fossiliferous marine con- glomerate 1.5–61 m above present sea level support a tsunami or- igin and indicate a runup of >400 m >6 km inland. The conglomerate age, 110 ± 10 ka, suggests a tsunami caused by the ca. 120 ka giant Alika 2 landslide from nearby Manna Loa volcano. [ABSTRACT FROM AUTHOR]