Sunday sand: lost worlds of El Dorado and Canaima

 
These are old, old sand grains.

Amongst the treasures that my friend Carla so generously provided me with, I was delighted to find sand from the River Carrao of Venezuela. The reason for my delight was that this river is part of the great Orinoco system and flows through the towering flat-topped mountains, the tepuis, of the Canaima National Park, a region that I am very familiar with (although, sadly, not directly - a destination still on my list).

The truly bizarre environments of these almost completely inaccessible plateaus were the inspiration for Sir Arthur Conan Doyle’s story The Lost World, the lost treasures of El Dorado – and a significant chunk of my book. To introduce the epic and multiple journeys that an individual sand grain can take, I explored the saga of what could indeed be one of the quartz grains in the images above. Here’s a sampling:

Think, for example, of a sand grain born, for at least the second time in its life, in one of the most remote and spectacular places on Earth, the Canaima National Park in southeastern Venezuela, near the borders of Guyana and Brazil. It has been resting for some hundreds of millions of years in a sandstone that is one of the oldest in the world. Two billion years ago, great rivers flowed across this part of what we now call South America, meandering, flooding, constantly changing their routes, just as the Amazon and the Orinoco do today. And, as rivers always have, they carried with them huge cargoes of sand, traveling hopefully, born from the disintegrating rocks of ancient mountains long since subdued and flattened.

These ancient South American rivers flowed, as most rivers do, over the continent to an ocean. But this early version of South America looked very different than it does today; small ancient fragments of continent had only recently been welded together to form the kernel of what would become today’s continent. Close to a couple of billion years would pass before the Andes were plastered along its western edge. The ocean to which the rivers flowed has long since been swallowed up and obliterated by the voracious churning of the Earth’s plates, today’s Atlantic being only a distant, indirect descendant.

As the rivers slowed on approaching the sea, as floods abated each year and channels changed their course, the rivers lost the energy to carry their cargo of sand and dumped it in sandbars, estuaries, deltas, beaches, and offshore banks. This process continued, year after year, over millions of years, and these abandoned layers of sand eventually covered a vast area of the fledgling continent. As the rivers roamed over the landscape, the layers built up in places to an enormous thickness, their foundation sinking to accommodate the load. Buried under this great pile, the sands were compacted and solidified into hard, rocky sandstone.

Much, much later, the continent, buffeted by colliding plates along its edges, was heaved upward again. The sandstones were back at the Earth’s surface and began their battle with the elements, a campaign that they continue to wage today, hundreds of millions of years later; these two-billion-year-old sandstones form the extraordinary landscapes of the Canaima National Park. Vertical cliffs a kilometer or more high protect vast flat-topped plateaus that look out over hundreds of kilometers of forest and savannah. The layers of sandstone once covered these areas, but they lost the battle with the elements and were stripped away. The mountains are the resistant remnants and have probably looked very much the way they do today for more than three million years.

Incredibly, in spite of all the geological violence going on around them—the split from Africa, the opening of the Atlantic, the rise of the Andes, and the splintering of the Caribbean—these sandstone layers remain essentially as they were deposited two billion years ago, not tilted but horizontal. It is this that creates the great flat-topped peaks, dissected and isolated by erosion around them, but toweringly intact. Sir Arthur Conan Doyle set his story The Lost World on these virtually inaccessible plateaus (tepuis, table mountains, in the local Pemon language), imagining them with dinosaurs and sandbanks “spotted with uncouth crawling forms, huge turtles, strange saurians, and one great flat creature like a writhing, palpitating mat of black greasy leather, which flopped its way slowly to the lake.” The true ecology of these plateaus is only somewhat less incredible. Long isolated from larger communities, many of the amphibians and reptiles that live here are found nowhere else in the world, including blind black frogs a couple of centimeters long. Nine hundred species of higher plants have been identified on one mountain alone, of which 10 percent are endemic. Thirty species of birds are unique to the area, and the task of describing the character and diversity of the insect life will continue to occupy entomologists for a long time. Many of the mist-shrouded summits in the park, which was awarded World Heritage status in 1994, remain completely unexplored.

There is of course, more – Jimmie Angel and the falls named after him, unique and isolated ecosystems, the hunt for gold that continues today with disastrous environmental consequences, and the epidemic of dam-building along the tributaries of the Orinoco. But enough for now – except that Carla tells me that these sands have been known to sing, or at least squeak. But that’s for another day.

 

[Carrao River image courtesy of Berrucomons at Wikimedia Commons, under the GNU Free Documentation License; the image description is “View over the Carrao river toward three small tepuys (from left to right): Kurun Tepuy (Vulture mountain), Kusari Tepuy (Deer Mountain), and Kuravaina Tepuy (Blowgun mountain)” – look closely, and you can see the sand banks along the river.]

 

 

Comments

[F]

Beautiful!

[Jules]

Michael,

You may be aware of this, but as I finished reading Jan Zalasiewicz's book The Planet in a Pebble this week, I looked at his suggestions for further reading and he highly recommended your book.

[Sandglass]

Jules - I'm almost finished Jan's book myself and was hugely flattered to find his comment on my own efforts. I hope to be able to put together a review of The Planet in a Pebble in the not-too-distant future.

Thanks for the note!

[Karen Sue Loader]

I enjoyed this beautiful, originally creative, and scenic journey. Are you freely sharing your images with others? I would like to come to enjoy these quiet moments of intrigue again that creates such a peacefulness as I survey all of the many wonders of the Lord the Creator God and all of His wonders to survey, which you capture so very beautifully. Thank you and may God Bless!

Happy Talents,

SunshineDreamer