Darwin Island - Geology

Geology

Darwin Island is the remains of an extinct volcano that reaches 165 meters above sea level, it is situated north west of the main Galapagos Island group on the Wolf-Darwin Lineament that extends from the Galapagos Platform to the Galapagos Spreading Center, a mid ocean ridge separating the Nazca and Cocos tectonic plates. The formation of Darwin Island is different from the formation of the main Galapagos Islands. There are currently two theories on the formation of the lineament: the first is that magma rising from the mantle plume forming the main Galapagos Islands has been channelled towards the Galapagos Spreading Center; alternatively there has been a separate rise in magma caused by stress in the ocean lithosphere by a transform fault.

Darwin Island is the most northerly of the two peaks on the Wolf Darwin Lineament that reach above the surface, the other island Wolf Island is approximately 40 km away, although there are other sub surface peaks. The volcano that forms the island is extinct, with the last eruption believed to have been approximately 400,000 years ago, making it younger than Wolf. The lava flows around Darwin are homogenous, believed to be because of its young age and have a similar chemical composition to those of the Galapagos Spreading Center.

Darwin is believed to have had at least two eruptive periods in its history of two tuff layers separated by plagioclase ultraphyric basalt. Evidence also exists to suggest that Darwin Island is the remains of what was once a much larger edifice. Since the eruptive phase this would have been eroded.

Darwin Arch is a natural rock arch would at one time been part of this larger structure is located less than a kilometre from the main Darwin Island is a well known landmark to the few visitors to the island.