Guide to Galapagos: Formation
One of the most interesting aspects of the Galapagos is the confluence of factors which made them what they are. But how did it happen?
The islands are a series of volcanoes. They were all formed by a single hot spot (at Fernandina Island).
That's a fixed point in the earth's mantle where magma spills out at the point where the Pacific & Nazca plates meet.
The Nazca plate then moves at 3 inches a year (give or take) steadily east towards the South American plate where it is subducted i.e. pushed down towards the earth's core.
So as the Galapagos Islands are formed they then start to drift east and sink beneath the South American plate.
Think of a slow moving conveyor belt set up over the top of a hot spot which is spewing out magma. Islands are formed then they drift off to the east, next island please?
So that's the geology of it - a series of remote volcanic islands in the middle of the Pacific.
Presumably a stroke of luck meant that this hot spot happened to occur at a point where three completely different oceanic currents converged.
The Peru current brings cold water life such as penguins, albatross and fur seals.
The warm Panama current enourages animals such as turtles, iguanas and dolphins.
Finally, the deep Cromwell current surges up with rich marine algae from the ocean floor to feed everyone.
So we have a remote archipelago at the crossroads of major oceanic currents with plentiful supplies of food.
Time to bring on the animals.
This is where you really come upon serendipity. In terms of behaviour, the animals are defined by the fact that they have really all washed up there together and by and large live symbiotic lives.
The Galapagos are the only remaining archipelago with an almost complete species composition. That's what makes them special.
It's really a question of some luck that lions didn't wash up there and just eat everything.
The best guess is that giant tortoises came down from Central America on the Panama current, floating on their backs. They can survive for up to a year without food or water so long sea voyages are not unlikely.
The iguanas presumably ended up here floating over on reeds or palm fronds.
Birds were perhaps blown off course during a storm and ended up settling here.
Marine life would have simply followed the currents and found a home with abundant food and decided to stay.
For this reason you have a unique mix of species - sea turtles swimming with penguins.
It is thought that the evolutionary changes evident in the islands indicate a longer time span than the islands can have existed.
That is to say that, extraordinarily, evolutionary time is longer than the geological age of the islands.
Today's Galapagos are therefore probably the second iteration of the islands. Version one is now under the ocean somewhere closer to the mainland.