Sunday, March 30, 2008

The Seismic Legacy of Volcan Barú

We live in the foothills of Volcan Barú (11,398 ft); we're at about 2000 ft; the pueblo itself, about a kilometer and a half away, is at 3200 ft. At the moment, Volcan Barú is a dormant volcano, but it wasn't always asleep. The last major eruption occurred around 500 C.E. but there was a minor eruption around 1550 C.E. In 2006, there occurred what geologists call an earthquake swarm, a series of minor temblors occurring over a short period of time. We felt one of them here in Potrerillos, which caused a certain amount of curiosity; minor temblors are frequent, although this was stronger than most. Still, there was no damage to our house, which is built in the traditional Panamanian style, and therefore pretty impervious to anything but a major quake. In Boquete, it caused a major panic, with people in the streets, screaming. Well, that's Boquete. We're a sturdier sort here in Potrerillos

The former eruptions left plenty of evidence around. The ground here in Potrerillos, more so than in Volcan or Boquete, is littered with rocks that range in size from huge boulders to small stones. We moved into our house in June, 2005. At that time, I hired a small backhoe to remove the worst of the rocks from the rest of the property (the house area had relatively few above ground) and move them to the quebrada area. The picture at the upper left shows what's left of those rocks--these are by no means the biggest moved. Behind the fence, you can just see the outlines of some of the huge boulders the backhoe moved to the edge, piling some on top of others in the expectation that we would eventually build a stone fence on that foundation. For various reasons that didn't happen. The rocks in the picture are part of a small mountain piled up by the backhoe. Those rocks and other removed from the ground manually by means of a tool called a coa were used to build our stone fences of the type so commonly seen in this area. There are some stunning examples that you can see as you drive up the carretera from David.

But these are a fraction of the rocks that still exist on the property. Especially this year, we've been making an effort to remove as many rocks as we can. Maintaining the property with power tools such as weed eater and lawn mower is the only way to keep the grass and jungle under control. But the rock problem was so bad when we moved in that we had to maintain nearly the entire 3 acres first by having it cleared by hand (2 workers with machetes) and then by weed eater. As we slowly cleared, we were able to introduce a lawn mower. We're still working at increasing the area we can do with the lawn mower; I'd estimate that we now maintain about a half acre by weed eater.

Unfortunately, there's more to it. This is ranching country, thus our cattle ranch neighbor. Bermuda grass grows rapidly here and is an excellent pasture grass. It's also one sign of poor soil. You would think that as a consequence of volcanic activity that, as a compensation for the rocks, we would have the benefit of rich volcanic soil. Wrong.

Actually, we don't so much have soil here; it's more of a matrix for small rocks and smaller stones, nearly impossible to grow anything with a serious root system. This particular piece of land was pasture before we bought it, although cattle hadn't been run here for a few years. There are trees; we have a swath of jungle anywhere from 50 ft to 80 ft wide that extends probably 2/3 of the length of the north end of the property. If we didn't mow and otherwise clear back there, the jungle would be much closer to the house than it is at present (about 30 ft away). And left to itself, the jungle would eventually reestablish itself even on the worst parts of the property that have so many small rocks and stones embedded in the soil that it can be problematical to walk--you do have to be careful--and murderous to weed eat--I recharge the line spool 2-3 times an hour, which is a LOT of line, but the rocks tear it up. Native (and invasive but benign) trees and shrubs do appear spontaneously, even in the worst areas, where I let them grow. A lot easier than weed eating!

Not all the problem is due to volcanic activity. The phrase "torrential downpour" was coined for the tropics and it certainly applies here in Panamá. We have watched in awe in September and October as the rain came down in sheets that made it impossible to see beyond the porch--for hours. We have no way at present of measuring the rainfall here, although we're getting a weather station in October, at the height of the rainy season. But near Panama City, the capital, rainfall in October and November averages 12"-13". We are probably slightly wetter here in Potrerillos. The rain can vary rather dramatically just within a few kilometers; we'll have rain here when it's not raining or raining mcuh less in Las Asequias about 6 km down the road.

One of the consequences of this hard rain is that it beats the living daylights out of the ground, causing spectacular runoff--and erosion. A lot of this area used to grow (and still does) sugar cane, which is hard on soil. Combined with the heavy rains and the fairly steep slope of the ground, I suspect that a good part of what we experience is due to erosion. But there's too much rock buried too far under the surface to be just that.

It means that even though I long to put in an extensive garden, this year was the first year I was able to do anything, because first we needed to build raised beds and haul in soil from outside--another story! I have been too busy doing maintenance, finding out where to get equipment repaired, seeing to (and working on myself) a fence to contain Fred, planting fruit trees and shrubs to do much about a vegetable garden. But this year I managed, with the help of Darío, our marvelous part-time gardener/general handyman and jack-of-all trades, to get two built using rocks we (and I mean we--I operate a mean coa) cleared from the ground. I'm terribly proud of our pepper and eggplant farm that you see here, with sweet potato vines in the foreground in the second bed. I cemented the upper layers of rocks in this masatera (flower/vegetable bed), simply because I wanted to make sure they would be able to resist the pressure of so much soil and water. It's not usual here to do so with fences--they're strictly "dry" stone fences, and for the most part, that's true of ours.

I've had to reduce my expectations of what we can do with this property, but I suppose that's all to the good. I spend a lot of time working around the property; maintenance takes up a serious amount of time. I am doing enough now in the veggie garden to keep me plenty busy; it's probably a good thing I really can't do a small farm. Really. I keep telling myself.

Addendum: I just looked up precipitation data from a weather station,, run by Lloyd Cripe over near Boquete. The climate is different there--I think we may actually have more annual rainfall here--but until we get our weather station, it's a guess. has only been in operation a year, but has excellent data for that time; for the month of October, 2007, the records show 34.81" of rain. We had abnormally high rainfall last year, so that's not totally typical, but it gives you an idea, anyway.

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