The analysis of mechanisms of subsidence of seamounts is often limited by inadequate information on the age of the seamount at the time it was first eroded to sea level. The ages of carbonates deposited on the eroded surface and the ages of the basalts therefore provide valuable observations for evaluating subsidence models. Such ages were recently reported for a small seamount in the Azores. It was found that the resulting subsidence was 100–150 m greater than could be attributed to thermal contraction of the ocean floor. This discrepancy can be attributed to stress relaxation within the underlying lithosphere. Viscoelastic models predict a subsidence that is a function of the effective relaxation time τ and the effective flexural rigidity D. Consistent parameters for 5–10 Ma old lithosphere are graphic and graphic.

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