Geology

The Galapagos islands are located in one of the most active oceanic volcanic regions on earth, It is located on the Nazca Plate, close to its junction with the Pacific and Cocos Plate. The islands are moving south and eastward at a rate of more than 7 cm/yr., which may not seem fast but would, over a million years , amount to 70 km of movement!
Where a sea floor plate is moving toward a continental mass, the sea floor plate is forced under the continent. This process is called subduction, occurs on the west coast of South America where the nazca plate is colliding with the American continent. There are many earthquakes along the Coast because of this process , the building of the Andes and the presence of volcanoes .
The evidence that the plate on which the islands sit is moving eastward is that the oldest islands are in the eastern part of the archipelago. There is also volcanic activity where the western island are now. In fact, it is on these Western Islands where all the recent volcanic activity has occurred, while the Eastern Islands are the oldest . The "Hot Spot Theory" states that in certain places around the earth, there are more or less stationary areas of intense heat in the mantle. These hot spots cause the crust to melt in certain places and give rise to volcanoes.
The Galapagos and Hawaiian Islands have mild volcanic eruptions where volcanic material comes out gently to form large lava flows rather than explosions. The molten magma forming these eruptions are made of basalt. The result of these type of formations gives the greatest combination of tropical volcanic islands , where you can see abundant marine life, as well as terrestrial fauna and flora , all in one unique diverse eco-system.