May 7, 2000.
The Geology of the Galapagos Islands- Part II
This Is Roger Payne aboard the Odyssey, speaking to you from the Galapagos Islands.
Last time I talked about how the Galapagos formed by the fusion of a series of underwater volcanoes. But I didn't have time to say that two undersea ridges lead away from the Galapagos: The Carnegie Ridge runs eastwards towards the mainland, and the Cocos Ridge runs northeast past Cocos Island to Costa Rica and Panama (the oldest part of it may perhaps even extend into the Caribbean). A short while ago, a sea mount in this ridge was found to be capped with smooth boulders. This indicated that it was probably once an island that was first eroded flat by waves (that's when the boulders got smooth) and later sank, as the sea floor on which it stood cooled and sank as well, until it reached its present depth of 2000 meters below sea level (over a mile down). If true, it seems likely that the hot spot which produced, and is still producing, the Galapagos Islands may have been active not for just five million years, but for ten or more million years.
Given our short lifetimes, ten million years seems like such a long time, but it is only one 450th of the earth's history, and therefore really a pretty recent event. Along with the Geologist Lyell, Darwin was one of the first people to appreciate that when enough time is available geological events that take place incredibly slowly create major features. For example, in the present case; for the island to have sunk 2000 meters and become a sea mount in 10 million years required a rate of descent of a fifth of a millimeter each year, that's less than an inch every 100 years. Yet the island is now a mile and a quarter down.
Darwin extended his thoughts of how long it took to accomplish extraordinary things slowly to the realization that given enough time, highly improbable things become highly probable.
When he was in the Galapagos he had recently been collecting fossils in South America. He had also started a separate notebook which he entitled "the Transmutation of Species.
In the summer of 1837, just under a year after he had returned from the Beagle voyage, he wrote in his diary; (quote) "In July opened the first notebook on Transmutation of Species. Had been greatly struck from about the previous March on character of South American fossils and species on Galapagos Archipelago. These facts (especially the latter) origin all my views." (End quote) The Galapagos Islands were the laboratory of Evolution that enabled Darwin to develop the ideas that changed the course of human history perhaps more than any other single discovery.
That's it for tonight. Next time I'll talk about how the strange species we see here may have gotten to the Galapagos in the first place. It's full of surprises.
© 2000 - Roger Payne