Elastic Flexure of Young, Overlapping Basaltic Lava Flows Offshore the Galápagos and Hawaiian Islands: Observations, Modeling, and Thermal/Chronological Analysis

Abstract

AbstractA recent multibeam bathymetry survey in the Galápagos archipelago revealed a novel observation between the islands of Santa Cruz and Santiago: a steep flexural moat formed between two volcanic flows, nearly 50 m deep and about 500 m wide. Submarine observations and elastic plate modeling are consistent with this feature forming after one inflationary flow overlapped another young flow, deflecting the underlying lava flow in what appears to be a classical elastic flexural pattern. We present a flexural analysis of this moat feature using a thin‐plate approximation to determine the effective elastic thickness of the underlying flow. Moreover, we propose that this elastic thickness serves as a proxy for the thickness of the cooling, solidifying upper crust of the lava flow at the time of deflection, a time‐dependent thermal property. This approach offers a chronological tool to put bounds on the elapsed time between two overlapping lava flows. We applied this method to the Galápagos moat to constrain the time history of its formation. Additionally, we identified and modeled seven additional flexural moat candidates in the Hawaiian archipelago and in the Galápagos using multibeam bathymetry. Elastic/thermal history analysis of these features yields relative time intervals between submarine lava flows ranging from a few years to about 600 years, which suggests that there is a critical time interval during which elastic deflection of the underlying lava flow may become “frozen in.” This methodology may provide helpful constraints on the temporal relations between overlapping lava flows wherever they form in relatively rapid succession.