Insights of long-term geomorphological evolution of coastal landscapes in hot-spot oceanic islands

Abstract

The Canary Islands form a volcanic archipelago in which a west–east (W–E) chain of progressively older and less ac-tive islands can be observed. In the Canary Islands, unlike most hot-spot archipelagos, certain geodynamic peculiarities have pro-moted longer periods of island survival, exceeding 20 Myr. This factor makes these islands a suitable context for this work, whichaims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islandsin different volcanic phases were selected: La Palma (1.8 Myr), Gran Canaria (14.5 Myr) and Fuerteventura (22.6 Myr). Anad hoclandform-based hierarchical taxonomy was designed to analyze the coastal geomorphic structure of the three islands. Based on amulti-sourced analysis in geographic information system (GIS) and field recognition, a comprehensive cartographic database wascollected using the coastline data-storing (CDS) method as a feature abundance proxy. Three different aspects of the geomorpholog-ical structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their com-parison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Compositionwas explored analyzing the distribution of the feature’s longshore frequencies (p). Abundance, by metrics of local abundance(N∩) and whole density (NU). Diversity, through four indices: normalized richness (S) and Margalef index (M) to estimate richness;Simpson index (D) and Shannon index (H’) to estimate evenness. We identified a systematic transformation in the dominant landformcomposition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The re-sults show a long-term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) overgeological time, as the coasts evolve from predominantly rocky-erosive to increasingly clastic-depositional environments. This long-term geomorphological pattern may be a general aspect of hot-spot island archipelagos, which can bring a new perspective to theknowledge of their coastal evolution. © 2018 John Wiley & Sons, Ltd.