Download Volcanic Origin of the Galapagos Islands Formation of the

Volcanic Origin of the Galapagos Islands
Formation of the Archipelago
The Galapagos archipelago is located in the eastern area of the equator line in the
Pacific Ocean, approximately 1 000 km away from the Ecuadorian coast. Just like the rest
of archipelagos of the world, it has a volcanic origin. Its origin is an exit point of magma
known as a hotspot which is beneath the earth surface. The eruptions produce lava that is
accumulated until it forms islands, which moves eastwards moving away from the point
where the magma is coming out.
The patterns of movement of the plates that gave origin to the Galapagos are complex,
but, in general terms, the big islands, which are younger, conform the western side of the
archipelago. The eastern islands are older.
The Nazca, Cocos and Pacific plates, and the topography of Galapagos.
In comparison with most of the rest of oceanic archipelagos, Galapagos is very young. Its
first islands were formed approximately 10 000 000 years ago, when the volcanic
eruptions started to open a path through the oceanic floor. Finally they formed submarine
mountains. The marine floor around the Galapagos Islands is formed by mountains,
heights, plateau and valleys. Satellite studies show the islands as the upper part of huge
submarine volcanos, many of which got united to form the submarine platform of the
Galapagos.
According to the theory of plate tectonics, the earth crust is
composed by several rigid layers of continental or oceanic floor
named plate tectonics. They all move about 10 cm per year due to
processes that occur in the depths of Earth.
The tectonic situation that involves Galapagos
represents the expansion of the oceanic floor, zones of
subduction and also transformation faults. The
situation in Galapagos is complicated because there
are three plates that are very close to each other: the
Pacific plate, the Nazca plate and the Cocos plate. The
Galapagos Islands are located over the Nazca plate,
very close to its union to the Cocos plate.
As a result of the moving of the floor, the islands move to the south and the east more than
7 cm per year. This doesn’t seem to be very much, but in a million years this might mean
the islands may have moved more than 70 km. One million years is little time if compared
to the estimate age of Earth (4 600 millions of years), especially when it is believed that
the oldest islands in Galapagos are 5 000 000 years old. The calculations estimate that
that the islands could have been formed at a distance of 350 km northwest from their
current position.
Volcanic Eruptions
According to the world patterns, the volcanic eruptions that occur in the Galapagos are
soft. This is because the volcanic material emerges gently to form great flows of lava. It
doesn’t emerge violently with explosions. This is because the melted rock or magma that
forms the eruption is formed from basalt, this means the lava doesn’t have a lot of water
and flows more easily than the eruptions rich in silica. The result is that the bigger
volcanoes of Galapagos tend to present soft edges with form of shields and rounded tops.
The magma that flows through a volcano emerges from inside of the Earth, and is formed
by melted rock and gases. While the magma emerges, the pressure of the rocks that
covers it decreases and the gases inside it try to escape. The gas can escape easily in
magmas of basalt, letting the melted rock, which in its majority doesn’t contain gas, flows
forming rivers of lava.
The younger volcanoes of Galapagos have an outline similar to a soup plate turned
upside down. Its heights are big depressions called craters. They are formed by the
sinking of the upper part of the volcano. This happens when the structure becomes weak
and the magma goes back. Most of these volcanoes were formed after a series of lava
flows. When the magma of basalt emerges to the surface, it is at 1 100 °C and presents a
red-yellowish color. The lava cools down in contact with the air and forms the crust.