Figure 1.

Map showing double chains of the Hawaiian hotspot

The bending of the Hawaiian chains started at ∼8 Ma. The Kea trend (north) is the original Hawaiian chain, whereas the Loa trend (south) is newly emerged as indicated by isotopic characteristics (see Figure 2). The Nihoa seamount (∼8 Ma) is the first volcano that has samples with geochemical signatures of the Loa trend, and it became clearly discernable at Kauai (∼5 Ma). Correspondingly, the volume and magma flux of the Hawaiian chain has increased dramatically since ∼5 Ma (Figure 1B). Volume flux is estimated based on the airy and flexural compensation models.^26,27 The latest eruption rate is ∼21 m³/s, i.e., 0.66 km³/year. Interestingly, double chains are also reported for the Samoa and the Marquesas volcano chains (Figure S1). Geochronology data from previous literature of the seamounts are compiled in the supplemental information.