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Easter Island, SE Pacific: An end-member type of hotspot volcanism

Luigina Vezzoli^1, and Valerio Acocella^2,

¹ Università degli Studi dell'Insubria, Dipartimento di Scienze Chimiche e Ambientali, via Valleggio 11, 22100 Como, Italy
² Università degli Studi di Roma Tre, Dipartimento di Scienze Geologiche, Largo S.L. Murialdo 1, 00146 Roma, Italy

Correspondence: E-mail: luigina.vezzoli{at}uninsubria.it

Correspondence: E-mail: acocella{at}uniroma3.it

Easter Island (Rapa Nui, Chile) is an intraoceanic volcanic island on the Easter hotspot, ~350 km E of the Eastern Pacific Rise. We match new field data with previously published age and petrochemical data to reconstruct the general evolution of the Island. This consists of three main volcanoes (Poike, Rano Kau, and the larger Terevaka), which experienced an overall similar and nearly coeval evolution, characterized by two periods: (1) buildup of a basaltic shield, culminating in the development of a summit caldera and the emission of more evolved highly porphyritic lavas (ca. 0.78–0.3 Ma); and (2) rifting along the shield flanks, by means of fissure eruptions (0.24–0.11 Ma). The trend of most eruptive fissures, NNE-SSW to NE–SW, appears to be controlled by the ~NE-SW elongated, emerged, and submerged morphology of the island. However, while the fissure-forming period at Rano Kau and Poike appears to be associated with reduced magma supply to the reservoir, at Terevaka it is characterized by the arrival of new basic magma, rejuvenating the system. The comparison to other intraoceanic volcanic islands suggests that, because of its tectonomagmatic features (low eruptive rate, scattered rift zones, and scarce lateral collapses), Easter Island represents an end-member type of hotspot volcano that is contrary to Hawaii, which represents the opposite end member.

Key Words: hotspot volcanism • shield volcano • caldera • eruptive fissures • rift zone