GEOLOGY

The islands are essentially the peaks of gigantic undersea volcanoes, composed almost exclusively of basalt. Most of them rise from about 2,000 to 3,500 m above the surrounding seabed, but over 7,000 m above the deepest parts of the adjacent ocean floor to the west of Fernandina. The highest summit is Volcano Wolf on Isabela island which is 1,660 m above sea level. Eruptions have taken place in historical times on Fernandina, Isabela, Pinta, Marchena and Santiago . The most active today are Fernandina, Isabela, Pinta and Marchena where fumarolic activity may be seen intermittently on each of these islands. The islands are also very gradually drifting eastward, due to the movement of the tectonic plate on which they rest. Hence the oldest islands lie to the east, including San Cristobal and Espanola which are approximately 3-3.5 million years old. The youngest islands, Fernandina and Isabela, are located in the west of the archipelago and have been in existence for some 700,000 to 800,000 years.

LAST NEWS
Galapagos: Fernandina erupts again
Early in the morning of May 13th 2005 the Galapagos Islands witnessed the start of a new period of volcanic activity. Studying satellite images, experts from the Geophysical Institute (GI) found a thermal anomaly on Fernandina volcano that had been previously undetected. The Director of the Galapagos National Park subsequently confirmed the information, indicating that a new volcanic eruption was taking place on the Galapagos Islands. During an observation flight over the volcano, the Galapagos National Park Service (GNPS) noted that the activity was occurring on a fissure on the Western side and reported the information to GNPS staff working in the area. They recorded a two kilometre-wide column of vapour and gases rising to a height of 7 km. There was also a high possibility of vegetation catching fire due to the flows of lava. Northerly winds carried ash from the volcano and deposited it as far as the Wolf and Ecuador volcanoes.

Fernandina is one of the most active volcanoes in the Galapagos. 1746m high, the island is the furthest West of all the islands and features a crater 6.5 by 5kms wide. The last eruption in January 1995 took place on the south-eastern side of the volcano, its lava flows reaching the sea. The eruption finished a few months later in April. Nearly all of the eruptions have taken place inside the volcano. However the last couple of eruptions have occurred on the sides of the volcano and lava flows have reached the sea on several occasions. The World Volcano Catalogue lists a total of 23 eruptions since 1813. The most famous of these occurred in 1968, with a massive collapse of the crater walls – only the second time that this natural phenomenon has been recorded.

Thermal images taken by scientists from the Geophysical Institute in March this year showed no signs that the volcano was about to erupt. The seismic station installed by the GI in 1996 to the extreme northeast of the island is currently out of service.

Source: Patricio Ramon and Hugo Yepes, Geophysical Department, National Polytechnic Institute
13/05/05