Galápagos Microplate

The entire Galapagos Microplate, which covers an area of 13,000 km², was formed to accommodate the motions of three major moving plates. Before the formation of the Galapagos Microplate, the Galapagos Triple Junction was a conventional ridge-ridge-ridge junction. The history of the microplate can be traced back to 1.4 million years ago, as evidenced by the trace of the southern triple junction ridge on the Pacific plate that constitutes the southern boundary of the Galapagos Microplate. At that time, the southern boundary of the microplate was then starting to form by an active hotspot located beneath the East Pacific Rise. The hotspot drifted from the Pacific Plate to the Nazca Plate approximately 1.2 million years ago and a seamount chain began to develop on the Nazca Plate. As the hotspot continued to migrate, rifting of the Nazca Plate developed along its track. This boundary is now known as Dietz Deep Volcanic Ridge, which extends to the northeast and grows at a velocity of 39 mm/year. The Dietz Deep Ridge terminates at the Dietz Deep Basin, an extensional feature with high elevational relief. The seamounts have been volcanically active with ongoing eruptions and continue to uplift the Dietz Deep Volcanic Ridge.

The local shape of the East Pacific Rise has varied with the development of the Galapagos Microplate. Approximately 1.5 million years ago, the East Pacific Rise was convex towards the west. Over time, the axis of the East Pacific Rise straightened and the triple junction began to migrate southward.[2]

The microplate is divided into two regions between north (Northern Galapagos Microplate) and south (Galapagos Microplate). The Galapagos Microplate is bounded by the Dietz volcanic ridge at 1°10'N, south of the Cocos-Nazca Ridge, and the Northern Galapagos Microplate (NGMP) is bounded by the Incipient Ridge at 2°40'N, north of Cocos-Nazca Ridge.[1][3] The westward propagating and slowly diverging Cocos-Nazca Ridge cuts between the two sub-plates toward the East Pacific Rise. However, the tip of Cocos-Nazca Ridge does not fully meet the East Pacific Rise[4] and, in fact, the westerly propagating Cocos-Nazca Ridge generates secondary transient rifts by shear stresses.[5][4] The tip of the Cocos-Nazca ridge has maintained a distance of 50 km from the East Pacific Rise and slightly moved its position into the eastern part of the microplate due to clockwise rotation of the GMP.