Tuesday, April 10, 2012

New Mexico Geology: Where Rocks Grow out of the Ground

I had this mostly written back in January, but then I got distracted and forgot about it. I will do my best to finish the New Mexico Geology series. Sorry for the delay

Almost a year ago I participated in a community service project called Eastern In Action, which is basically a beautification project for the town, and if you had ever seen a town in Southeast New Mexico you would think that would be sorely needed. Unfortunately, there is no oversight process so anybody can ask for help, so instead of being sent to help the elderly, disabled, or disenfranchised who needed the help, my group was sent to help a well off farmer in his fields. Now besides doing 'charity' work for a man who could afford to pay for that service, I was most annoyed at the fact that the problems in his fields were his own fault.

Why you might ask? Well you have to understand that the area I live in has a classic arid soil referred to as caliche soil. Caliche is easily identifiable due to the layer of calcite at varying layers within the soil. So what does this have to do with the greedy farmer? I'm getting to that; calcite dissolves in water so on the rare occasion that we do get rain, the mineral goes into solution, and then in the more common high heat, the water evaporates and as it does it pulls the calcite towards the surface. So when the farmer was watering his fields he was speeding up the caliche forming process, pulling up the calcite very quickly and creating numerous evaporite rocks in his fields. Thus we toiled in his fields for several hours in order to rid the field of the rocks he created.

Moral of the story? Mostly that trying to grow water intensive crops in an arid (well semi-arid, but it feels like a desert) environment is not a good idea. However, if you feel like doing so learn from the cultures who have been successful in that goal. One such group are the Mormons in Utah.  When they built their society in Utah the only water they had access to was from the Great Salt Lake, so in order to water their crops without salting the land and rendering it useless they saturated the soil pushing the salt deeper into the ground away from the plant roots. However, when there is very little water to go around this doesn't work, and since we rely on fossil aquifers this solution is unworkable and would kill the area..

However, here are a few photographs of a cut into the soil, with the caliche soil is brilliantly displayed.

The white rocks are evaporite calcite minerals

This is right above the main layer, with a hammer for scale

Here is the main layer with a hammer in it
 So this is probably the most interesting geology near the college, but there is one more thing. The area is a very slight valley and this is because it was once a large meandering river. The water dried up after the last ice age when the Pecos River was formed; this River is much faster and thus moved up through what is now New Mexico and pirated the ancient streams that once flowed off of the Rio Grande Rift.

After the river was cut off, some of its water was stored in the sands it once carried forming a perched aquifer (an aquifer sitting on top of an impermeable layer) so when settlers first came to Portales they had ample water and like all humans they quickly depleted them. In fact there used to be year long lakes in Portales where the ground dropped beneath the water table, something most of the students at the university would find quite surprising. Well I exaggerate, there is still one aquifer that hasn't been depleted, but the geniuses out here put a dairy on top of it because there is no way that the dairy could pollute the aquifer with E.coli.

Luckily we do have the Ogallala Aquifer to fall back on

Right there, where the star is, you know where it is losing water instead of recharging. Hey, can I come live with one of you? I don't think there is going to be much water here anymore.

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