Guatemala: A Microcontinent All Of Its Own

Vulcan de AguaGuatemala occupies a strange place on the map of the world. Take a look at it. The best way to understand Guatemala geographically and geologically speaking is this: picture a very fat reversed capital “L.”

Across the bottom, horizontal, line is the Cordillera, a very high mountain range created by the subduction of the Cocos plate under the Caribbean plate, for good measure the North American plate pushes down on Guatemala. Most of the rocks in this range are igneous, usually volcanic but there are some places in Guatemala where one can find mantle rocks. Mantle rocks are rocks created when the plates separate in the deep mid-oceanic ridges and eons later, after moving across the bottom of the ocean, are thrust high up into the skies by continents colliding. This is why you find fossilized seashells in the Dolomitic Alps, which once were a great coral reef. Mantle rocks are found, exclusively in mountains where they have been uplifted, like Cyprus, California and other places. California’s serpentinite is a good example, as seen in two photos attached, one close-up and the other an outcrop near Yosemite National Park.

Like most “highlands,” languages proliferate, such as in the Caucasus and Papua New Guinea, which both have hundreds of languages. In Guatemala there are roughly 20 languages up in the mountains, which is one good reason to return: just to see and experience so many different cultural groups crammed into one small area. I do not know the native dialect the Mayans of the Peten region; I’ve been told it’s Yucatecan, but I’ve also heard of at least two more Mayan languages, both of which I could never pronounce, even if I tried. I will discuss the languages of Guatemala, later, in a separate post.

More dramatically, along the east-west axis of the bottom line of our “L” volcanoes are very common. In fact, I am looking at one right now.

SerpentiniteThe vertical line of our imaginary capital “L” is karstic, limestone, hilly, eroded, uneven and covered in a blanket of deep pile, luxuriant green jungle. The vertical “L” is also mostly one geological unit: the North American plate’s margin, a vast limestone plateau and former seabed of soft, malleable rock. In some places Karst topographies can take wild shapes, like the area around Guilin, China and Ha Long Bay near Hanoi, Vietnam. I’ve also seen some strange karst in Belize, but have no photos. This kind of geological unit is also prone to sink holes and caverns, hence the perpetual fascination with sinkholes that just “appear” in Guatemala. (Side note: sinkholes, or cenotes, also serve as great places for archeology, as the Classical Maya used them as garbage dumps.) Peten Itza, the lake we stayed on in Flores, is a shallow depression in this geological feature that has filled up with water. This limestone is not, as the geologist would say, a competent rock. A product of uneven, unsteady erosion the lake is proof of the incompetent rock.

Now, run a diagonal line at 45* between the vertical line and the horizontal: this northeast to southwest running line roughly corresponds to the Rio Motagua valley, the main river that drains this massive rain shadow valley. The valley is semi-arid, complete with cacti, other succulents and sandy soils that are perfect for growing the tasty cantaloupes and honeydew melons. As I mentioned earlier this valley is smashed between three mighty geological units: the Cocos Plate, the Caribbean Plate and the North American Plate.

I mentioned all of this mostly for your edification, but also for two separate but fascinating reasons.
Serpentinite
First, as we were driving down the valley, literally down, but bearing northeast, I spied what looked to be like green rocks to me. A clear hint of the trauma the rocks in the hills have undergone were the shattered roadcuts, outcroppings and multiple faults visible in the roadside. Imagine what the underlying rock looks like? This little country is the earthquake hotel and its own microcontinent all rolled into one.

Some of the stone was hard igneous, some was sandstone, some metamorphic and other plain limestone. But here and there about halfway down the mountains green rocks proliferated. I simply had to stop and look at the rock. Indeed, it was serpentinite.

“Now,” you ask, “why do I give fig about a green rock?”

Answer: there is a very special element that precipitates through serpentinite. Its abbreviation in the Periodic Table is “Au,” and the Spanish had a sickness for it that destroyed two great empires and countless smaller societies. Over time gold will, indeed, given enough pressure, rain through serpentinite. It’s one of the chief reasons so many people went to California in the 1840s. Further, I have a hunch, although my geological knowledge is only basic, that this serpentinite I was looking at was probably a proto-jadite stone, which would make sense because jade was more valuable to the Mayans and Aztecs and Zapotecs than was gold, or silver.Crustal Collision Zone

The second reason is this photo  (also pictured in the post) I took on the flight from Flores to Guatemala City this morning. Take a look at it. It’s a collision zone, where the soft margins of the North American plate are running into the harder rock of the Caribbean and Cocos. The mountains look like you’ve shoved a carpet against the wall. One narrow valley is even more interesting. I suspect what’s happened to it, the one that looks kind of like a ladder, is that the rock was pushed together and then pulled apart briefly creating stretch marks, and then pushed back. (This feature can be seen in the Appalachians, as well, which are extremely ancient mountains compared to these in Guatemala.)

The next question, which I am unqualified to pretty much even speculate on, is how the geology and geography effects politics. I reckon I’ll be needing to call a buddy of mine in Austin who is a Guatemalteco and ask him.

More soon . . .

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