Monday, September 16, 2013

How the Amazon Fills Up

Well, I was thinking about ayahuasca, brujeria, Matses' stealing people who became my friends, and the rise in the Amazon annually and had about 10 pieces I wanted to write. But dinner--simple sauteed/baked chicken breasts with a light sauce of garlic, olive oil, diced onion, tomato and capers with a side of small baked red potato and an organic arugula/greens salad with a nice balsamic vinagrette--is cooking so I only have time for one story.
     So here is the story of how the Amazon Basin fills up every year, rising up and sustaining an eight to 13 meter increase in height for several months--and having that rise and sustained water happen all over the entire Amazon Basin--close to the size of the entire USA--at the same time.
     While I'm not an hydraulic engineer, this is what I see happening: The Andes mountain on the West of the basin, and the north ridge of South America fill up with water during the wet season. In the Andes, particularly, that water freezed either inside the mountains or atop them as snow. Now you might imagine that when those mountains begin to thaw, the Amazon would start to fill up from just east of those mountains and that water, via the river system, would make it's way across the continent over the next several months. But that's not what happens. When the water rises three feet or three meters in the rivers closest to the mountains, it's also rising simultaneously--or within a couple of days--all across the basin.
     What's happening is similar to your old high school experiment, where you put two small plastic tubs next to one another and made holes between them to connect them. Then you put several sponges filled with water in one of them: The water drained into the second plastic but never overflowed. And as the water in the second plastic evaporated, the sponges put out more, until there was an equal amount of water in both plastic tubs. And at that point there was no more draining from one to another.
     So how do the Andes simultaneously feed rivers nearly three thousand miles apart? Well, it's got to do with the makeup of the mountains and underlying stone of the basin: It's primarily limestone. And limestone is soft enough that water will work it's way through, making tunnels, carving out vast lakes within the mountains and so forth. But the limestone is also beneath the basin and so there are little straw-like tunnels--and larger ones as well--that run from the Andes to the East Coast of Brazil. And those tunnels fill up with water at the same time the rivers on the west do, and feed out through beneath the ground--particularly into lakes, swamps and rivers--filling the entire basin simultaneously.
     Rains may raise a river a meter or two for a day or so, but then that water has washed downstream, and if that were the primary device for filling the rivers and lakes, the lakes on the Western side of the Continent would be empty once the rains stop. But they're not. And that's because they are filled by thousands of springs--holes in the limestone tunnels beneath the basin. And in some lakes you get the fantastic effect of hot and cold springs, by the hundreds, within a few feet of one another. The hot springs are fed by rivers that have been exposed to the warm air; the cold springs are fed by water that's been frozen for months and has never seen the sun since it was rain.
     And that's how the Amazon does it.
     You can all return to whatever you were doing now.

1 comment:

Devon Wright said...

love it, thanks for the good read!