Large-scale mass wasting on small volcanic islands revealed by the study of Flores Island (Azores)

摘要: Small intra-plate volcanic islands (total height above seafloor <2500 m) have been considered gravitationally stable. Topographic, stratigraphic, structural and new K/Ar data show that the small island of Flores (Azores) is strongly asymmetric made up nested successions. Along northwestern coastline, ca. 1.2 Ma lava flows are in lateral contact with a younger unit (ca. 0.7 Ma), reflecting existence steep discontinuity. From general dip flows, their age arcuate geometry contact, we infer major landslide removed western flank older volcano. Further inland, E-dipping at summit 1.3 Ma, suggesting another structure displaced whole half former edifice. Available offshore large hummocky field west Flores, here interpreted as voluminous debris-avalanche deposits. Unlike eastern central Azores islands, sits on relatively stable tectonic setting. Therefore, propose small-size can be sufficiently unstable to experience recurrent episodes large-scale mass wasting triggered by mechanisms other than earthquakes thus represent an under-evaluated potential source hazard and, therefore, risk.