Galápagos Geology

     The Galápagos are a group of volcanic islands located above a hot spot near the intersection of the Nazca and Cocos tectonic plates.  The dominant type of volcano found on the islands is the shield volcano, some of which contain huge calderas.  Historically recent volcanism has occurred on Alcedo, Cerro Azul, Fernandina, Floreana, Marchena, Pinta, Santiago, Sierra Negra, and Volcan Wolf.  Some islands, such as Santa Cruz and San Cristóbal, have been active in recent geologic time, yet also show evidence of volcanism occurring as far back as over two million years ago.  The Galápagos Islands are home to many "textbook" examples of volcanic landforms, including the spatter cone, tombolo, caldera, and pahoehoe and aa lava flows.
 

Magill at Post Office Bay
  Matt on the beach of Isla Rábida, with stratified tuff in the background
  Magill, astounded by the beauty of the Sierra Negra caldera, Isla Isabela
  Fumarole on Isla Isabela
  El Grupo Whitman on top of Isla Bartolomé, looking west toward Isla Santiago
(tombolo in the background)
  Kate and Magill swallowed up by pahoehoe on Isla Santiago

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