STRI Tracks Mountain on the Move in Colombia

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The Sierra Nevada de Santa Marta, a UNESCO world heritage site just 26 miles off the Caribbean coast of Colombia, is the tallest coastal mountain in the world. It's peak towers at 18,942 feet, and it hosts 36 different streams and rivers.

No human force—be it faith or muscle—could move such a mountain. Nevertheless, the mountain has moved.

A recent collaborative study from researchers in Colombia, Europe and at the Smithsonian Tropical Research Institute (STRI) reveals that the Sierra Nevada de Santa Marta has traveled 1,367 miles from northern Peru to its current location over the past 170 million years.

One major indicator that the mountain had moved was discovered using a technique called paleo-magnetism, which analyzes the direction in which certain types of rock crystallized. (Crystals are influenced by the Earth's magnetic field.) "The magnetic signature of these rocks says that they cannot be from where they are right now," says Agustin Cardona, a postdoctoral research fellow with STRI and one of the authors of the study.

The study shows that the Sierra Nevada de Santa Marta began its initial move from northern Peru due to pressure by the tectonic plates of the Pacific. Over millions of years, the mountain moved constantly, undergoing periods of more accelerated movement, and finally joining the Colombian Andes. Then, around 45 million years ago, the Pacific plates isolated the Santa Marta from the Andes, pushing it all the way out to the Caribbean coast.

By measuring the depths of specific minerals (silicon, for example) in the rock, researchers were also able to date some specific parts of the mountain. They discovered that its ancient foundation is over one billion years old, dating to the Pangean supercontinent. They also learned that the mountain contains many rock fragments that were uprooted in the course of its journey. This is likely responsible for the equally fragmented fossil record of the Santa Marta area.

"The next step is to test which fragments have moved, and which have stayed in place," says Cardona. "Then we'll have a truly robust paleo-geography for the region."

With this complete geological history, Cardona says scientists will be better suited to understand the specific effects of global phenomena such as climate change on the highly biodiverse environment of the Santa Marta mountains. The mountain's height, combined with its tropical location, has created numerous microclimates that provide habitat for many rare species, including 46 amphibian species and 628 different species of bird, not to mention unique mammals like the giant anteater and the white-lipped peccary. Some 26,500 indigenous people also live on the mountain, including the Kogi, Arhuaco and Wiwa tribes, among others. "This is a living, breathing, mountain," says Cardona.

And the mountain is still on the move. Though the Pacific forces have stopped acting on it, the tectonic plates of the Caribbean are now pushing the mountain. The entire region is slowly shifting towards the Caribbean, and is not scheduled to stop anytime soon. Of course, we will barely notice the change during our lifetimes. But the odyssey of the Sierra Nevada de Santa Marta will continue nonetheless.

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