Laminated into mountains over the course of a billion years

Earlier this month, the New York Times took its readers to Angel Falls, Venezuela, and onto the terrain of a lost supercontinent called Gondwana.

[Image: A remnant glimpse of a lost supercontinent, via the New York Times; photographer unknown. "The path in some stretches was completely overgrown with trees, reminding me how oppressively dark the jungle can be," we read].

Throughout Venezuela, we read, there are dozens of sandstone mesas, or tepuis. Tepuis are the "remnants of what geologists believe were the mountains of the ancient supercontinent known as Gondwana."

Incredibly, some of these "isolated mesas," as National Geographic describes them, "are two billion years old, preserving an array of unique plant and animal life that rivals that of places like the Galápagos."

According to the New York Times, some of the "distances involved" in flying from one mesa to the other can be so extreme that many species of bird cannot make the trip; each mesa thus acts as a kind of evolutionary island, where genetic lines develop in complete isolation over thousands of generations. Weird birds and flowering plants thrive. Studying these sites might therefore give us a glimpse into "what the world was like more than a billion years ago."

That last quotation is from Charles Brewer-Carías, a man the New York Times says is "a Caracas-based naturalist and explorer who is an eminent expert on Auyantepui and the country's other mesas." He is also an "ex-dentist."

In fact, during no fewer than "186 expeditions into Venezuela's backlands, Mr. Brewer-Carías has discovered the world's largest sinkholes, on a tabletop mountain called Sarisariñama, and practiced dentistry among the Yekuana tribe, whose language he speaks fluently." And he's still going: "Accompanied by Czech speleologists" in early 2006, Brewer-Carías "documented what may be the world's largest quartzite cave."

In any case, it's the tepuis that fascinate me here; these "sandstone mountains," Brewer-Carías explains, "are the majestic leftovers of an enormous washover of sand that came from Africa." This makes them "a window into what once was Gondwanaland" – that is, they are laminated dunes of a lost desert – the remnant geography of a world that no longer exists.

(Vaguely – in fact, more or less not even slightly – related: Z).

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2 Comments:

Anonymous Anonymous said...

The statement that these mountains are "two billion years old" is incorrect I'm afraid. Although they are composed of rocks that are billions of years old, the formation of the current mesa and mountain landscape is much more recent. In the order of a few millions of years, and related to subduction of the Nazca plate and the formation of the Andes. It's unfortunate that author of the NYT article has passed on such a fundamental mis-understanding. This seems to be a unfortunate symptom of current science journalism where the journalist do not have adequate education in the topics on which they report on....discuss...!

January 28, 2007 7:09 PM  
Blogger hlebar said...

one of those tepuis has a cave that goes all the way through it - it's speculated this is the remnant of an underground river system

January 28, 2007 10:45 PM  

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