Day 3

Day 3: (0.37°S 91.55°W)

It took over a week of sailing for us to finally get here, but we arrived in Santa Cruz, the most populated of the Galapagos Islands, this morning! (The entire island chain only has a population of about 23,000) We had to travel all the way across the Pacific Ocean because the Galapagos are at the very eastern edge of the Pacific. I learned today that they are located at the northern edge of the Nazca Plate at its border with the Cocos Plate. On its east edge the Nazca plate borders with the South American plate. The Nazca plate is slowly moving south east away from the Cocos plate and into the South American plate. The Nazca plate is subducting under the South American plate. The Nazca plate is forced into the mantle, which is made of very tough and thick liquid rock. The outer parts of the mantle are coolest but as they near the center of the earth they become very hot and less solid.  As shown in this picture: 

http://en.wikipedia.org/wiki/File:Earth-crust-cutaway-english.svg

The Nazca plate melts when it is forced into the hot mantle, then its melt products make their way up to the surface and create volcanoes. The Andes were formed when the South American plate crumpled and rose up over the Nazca plate, they are highly volcanic. This movement of the Nazca plate also created the Galapagos Islands.  The Galapagos are thought to be produced by a mantle plume, which is a column of hot rock that rose from deep within the earth because it is hotter and less dense than surrounding rock.  Scientists believe mantle plumes must originate from very deep within the earth because they stay still relative to each other over tens of millions of years even though the lithospheric plates above them move around. The plume burns through the earth’s crust and creates a underwater volcano which eventually grows to an island but because the Nazca plate is moving the island eventually moves off of the hot spot (the plume) which makes room for a second volcano to form and then this one moves making space for a third and on and on.  In this picture you can see how the plate moves to the left after a volcanic island is formed and then a new one is formed:

http://people.rit.edu/rhrsbi/GalapagosPages/Vulcanism2.html

Though the Galapagos are among the most active volcanoes in the world they are not very seismically active. Eruptions in the Galapagos have taken place in historical times on the islands, Fernandina, Isabela, Pinta, Marchena, Santiago, and Floreana. The island chain is expected to keep on growing and adding new islands, while some of the old ones will submerge into the sea. The most recent volcanic eruption in the Galapagos was in April of 2009 on Fernandina, one of the youngest islands.  Check out this video of the eruption: 

http://www.youtube.com/watch?v=2PRkSFkxgmw

This picture shows Isabela from above, it’s one of the youngest islands.

http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/Galapagos_page.html

I gotta get some sleep, it's been a long day! Will post again soon.

Love ya'll 

Nancy