How was the Galapagos Archipelago formed?

How were the Galapagos Islands formed?

 

The islands are located in the eastern Pacific Ocean, 973 km (525 nmi; 605 mi) off the west coast of South America.  The closest land mass is the mainland of Ecuador to the east (the country to which they belong), to the north is Cocos Island and to the south is Easter Island and San Felix Island.

The islands are found at the coordinates 1°40′N–1°36′S, 89°16′–92°01′W.  Straddling the equator, the islands in the chain are located in both the northern and southern hemisphere with Volcan Wolf and Ecuador on Isabela being directly on the equator line.  Española the southernmost island and Darwin the northernmost island are spread out over a distance of 220 km (137 mi).  The Galápagos Archipelago consists of 7,880 km² (3,040 sq mi)  of land spread over 45,000 km² (17,000 sq mi)  of ocean.  The largest of the islands, Isabela, measures 4,640 km² (1,790 sq mi)  and making up half of the total land area of the Galápagos.  Volcán Wolf on Isabela is the highest point with an elevation of 1,707 m (5,600 ft)  above sea level.

The group consists of 15 main islands, 3 smaller islands, and 107 rocks and islets.  The islands are located at the Galapagos Triple Junction.  It is also atop the Galapagos hotspot, a place where the Earth’s crust is being melted from below by a mantle plume, creating volcanoes.  The oldest island is thought to have formed between 5 million and 10 million years ago. As the plate moves the hot point does too, that's why some islands are still in formation process. The youngest islands, Isabela and Fernandina, are still being formed, with the most recent volcanic eruption in April 2009 where lava from the volcanic island Fernandina started flowing both towards the island’s shoreline and into the center caldera.

The Galápagos are located on the very northern edge of the Nazca plate, which is bounded by the Cocos (north), the Pacific (west),the South American (east), and the Antarctic (south) plates (see map below).  The Nazca plate itself is currently drifting southeast. The absolute motion of the Nazca Plate has been calibrated at 3.7 cm/yr east motion (88°), some of the fastest absolute motion of any tectonic plate.