Galapagos Oceanic Plateau

The Galapagos archipelago is the exposed tips of ocean island volcanoes that together have built an oceanic pleateau edifice. These ocean island volcanoes have formed in a complex tectonic setting with magmas of different provenance. Deep mantle magmas are sourced from the Galapagos Hot Spot (relatively a diffuse warm spot) and shallow mantle magmas are associated with the Galapagos Spreading Ridge to the north of the archipelago. The Galapagos archipelago is sited on the Nazca Plate, which is moving at 3.7 cm/yr to the ESE over the Galapagos Hot Spot. Complicating this setting further, the Galapagos Spreading Ridge has been drifting NE for more than 10 Ma and between 5 and 8 Ma was sited directly over the Galapagos Hot Spot.

This dynamic interplay of hot spot and mid-ocean spreading ridge settings has given rise to a complex geology across the exposed archipelago. Four provinces are recognised that have different ages and magma provenance.

[1] The Western Province has currently active hot spot magmatism (0.0-0.75 Ma) on Fernandina, Roca Redonda and Isabela Islands.

[2] A Central Province of recently active (0.0-1.5 Ma) hot spot volcanism has mixed magma provenance with minor spreading ridge affinities. Central Province islands include Santiago, Rabida, Bartolome, Pinzon, Santa Cruz and Floreana Islands.

[3] An Eastern Province consists of older (1.1-2.8 Ma), extinct and eroded hot spot volcanoes also of mixed magma provenance. These volcanoes have subsided significantly below sea level with drift off the hot spot high, leaving off shore remnants of tuff cones that originally formed near the coast line. Eastern Province islands include SW Cristobal, Hood (Espanola), Santa Fe and Baltra Islands and the NE margin of Santa Cruz Island.

[4] A Northern Province of recently active (0.0-0.7 Ma) volcanoes with mid-ocean spreading ridge affinities is in close proximity to the Galapagos Spreading Ridge. Northern Province islands include NE Cristobal, Genovesa, Marchena and Pinta Islands.

ITAR undertook two expeditions in the archipelago in early 2009 to coincide with the 200^th anniversary of Charles Darwin's birth. The aim of this fieldwork was to document the geology and volcanic processes evident at each of the terrestrial sites open to the public. This was part of the broader ITAR research stategy to investigate first hand a range of active tectonic settings, including oceanic plateaux (Galapagos) and continental magmatic arcs (Peruvian Andes), that are significant to models being developed for older provinces being investigated by ITAR (i.e. Yilgarn Craton [1]). The opportunity to undertake fieldwork in Galapagos was made possible by Wendy Meijer and Enchanted Expeditions who made all logistic arrangement to support the fieldwork. The guides Monica Plaza and Darwin Alvarez are thanked for sharing their profound knowledge of, and enthusiasm for, all things Galapagos. The professional crews of the "Beluga" are thanked for making it all happen and the fellow expeditioners are thanked for their shared observations, insights and fun conversations.

Below are links to diagramatic representations of most of the different sites open to the public in the archepeligo and different volcanoes and geological features. These are intended for general interest only and contain numerous errors, omissions and are not correctly scaled. More detailed accurate geological maps and report on the geology of the archipelago for the general public will be posted on this site in the future.