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 The
Galapagos Islands are thought to have formed about 3-5 million years
ago, relatively recent in geological terms.
They probably are the product of volcanoes that formed beneath
the sea and which continued to rise until they broke through the water's
surface and became islands. The islands on the east, especially the Island of Espanola,
seem to be much older than the western islands by a million years or so.
This is consistent with the "hot spot theory," which theorizes
that the Galapagos are situated right over a "hot spot," an area
of extreme heat within the earth's mantle. As the tectonic plates on which
the islands are placed move (at a rate of about 3 inches a year), magma
from these hot spots wells up through the new boundaries, forming a string
of new islands as well as causing earthquakes and several volcanic eruptions.
Today,
the Galapagos are one of the world's most active volcanic areas,
with over 50 eruptions in the last 200 years.
The most active volcanoes are the ones on Fernandina, which
last erupted in 1995, and the Cerro Azul on Isabela, which last
erupted in October 1998. All
of the volcanoes are still active (with the exception of the Ecuador Volcano
on Isabela Island), but most of the eruptions have been small.
 Other
common geological activity includes uplifts, which are caused when
magma beneath an island hardens and lifts the land through and above the
waters surface, and large depressions called calderas, which happen
when magma beneath the summit of a volcano cools and contracts, causing
the entire peak to collapse inward.
For
a closer look at volcanoes and their fascinating features, special
tours are available to the rim of the Alcedo Volcano, with
a spectacular view of the caldera, and a 1-2 day trip to the rim of the
Sierra Negra Volcano, the oldest volcano on Isabela Island.
There are also many hikes to and around different volcanoes, such
through the Highlands of Santa Cruz Island or the Sugarloaf
Volcano on San Salvador Island.
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