Geology

The Galápagos Archipelago is a hotspot volcano chain created by eruption of lavas sourced from partially melted mantle rocks. These rocks partially melt as they decompress within an upwelling of anomalously buoyant mantle material beneath the islands (i.e., a mantle plume). The physical location and geometry of the mantle plume upwelling (and thus melting) is complicated by the Galápagos Spreading Center (GSC) located only ~200 km north of the Archipelago. The GSC is a mid-ocean ridge where two tectonic plates (Nazca and Cocos) spread apart forming new oceanic crust. Initially relatively warm, the newly formed crust and underlying mantle cool as they spread from the GSC, forming a sloped boundary capable of perturbing the flow of the mantle plume and altering the pattern of volcano formation and evolution. Such interactions between the tectonic plates, the GSC, and the upwelling mantle plume control the formation and history of the Galápagos Archipelago.

Despite the above general picture of the geologic processes at work to form the Archipelago, our understanding of the islands growth and distribution through time is vague. Geologic models for the formation and eventual subsidence of islands in the Galápagos rely on sparse age estimates from lava samples collected across the archipelago and basic models of plate dynamics. These data are challenging to interpret because ages often overlap and physical parameters (e.g., the elastic properties of the lithosphere) necessary for modeling are difficult to constrain due to lack of data, both from the islands and the submarine areas around them. Fortunately, a more robust and potentially accurate framework for understanding the dynamics of island formation in Galápagos could be generated by combining geological, biological, and climatological data.