Abstract. Long-term coastal erosion is not yet well studied given
that it is difficult to quantify. The quantification of long-term coastal
erosion requires reconstruction of the coast's initial geometry and the
determination of where and when the erosion started. Volcanic islands
fulfill these two conditions: their initial shape is roughly conical and the
age of the lavas that generated this geometry is easily measured. We have
developed a method to reconstruct the initial shape of simple volcanic
edifices from aerial and submarine topographic data. The reconstructed
initial shape and associated uncertainties allow us to spatially quantify
the coastal erosion since the building of the island. This method is applied
to Corvo Island in the Azores archipelago. We calculated that, due to
coastal erosion, the island has lost a volume of 6.5 ± 2.7 km3
and roughly 80 % of its surface area since it first came into being. Taking the
large uncertainty in the age of the topmost lava flows (0.43 ± 0.34 Myr) into account, we have estimated that Corvo Island has lost an average of
5000 to 100 000 m3 yr−1 of its volume due to coastal erosion.
Lastly, we show a strong correlation between long-term coastal erosion and
the spatial distribution of the waves. Specifically, we highlight a stronger
control on erosion by smaller and more frequent waves than by storm waves.
The next step will be to apply this method to other volcanic islands in
order to (i) streamline and improve the method and (ii) verify the
correlations observed in the present study.
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