Thursday, January 29, 2009

Dirt 101

My mom will forever take the credit for my becoming a soil scientist. "Remember that time I drove the car on that construction site to see what kind of dirt piles those were?" She'd reminisce. Of course I was 12 and MORTIFIED that my mother would look at dirt.

Alas, I love it so. I like to dig too, but I'll cover that some other time when I'm discussing shovels. (I promise I will discuss shovels as my love for Razorback sharpshooters knows no bounds.)

Soil is a total sensory overload for me. It smells good (there are exceptions, I'll get there) and it's pretty. A way of categorizing or classifying soil involves a tool called the Munsell Color Book. It's a book of dirt-colored paint chips. Munsell color covers the entire visible spectrum, but the soil colors are generally in the red-yellow-brown-grey family. Also neat about soil are the terms. Soil scientist get to use technical terms like "mud--a mixture of soil and water, muck--finely decomposed organic matter, and gley--grey color from reduced iron.

This is an ash soil from nearby Kruzof Island. Isn't it pretty? Now, technically, this isn't soil it's parent material, but it's so striking. All the layers are cemented together by iron and aluminum oxides that leach out thanks to 150 inches of rain.



These layers are from several bursts from Mt. Edgecumbe and crater mountain. Most of the volcanic activity is from about 11,000 years ago.

Below, is an actual soil. She's a cute lil spodosol. Her name is Sarkar and she's from limestone parent material.



Spodosols are the rainbows of the soil world. They almost always have striking white, black, and red horizons. Layers in soil are called horizons.

That tool pictured is a U-dig-it. I wear it on my belt the way some folks have leathermen or cell phones. I'm cool like that.

I said not all soils smell good. That good, earthy, dig-your-toes-in smell is actually from a microorganism called actynomycetes. This little critter is responsible for breaking down organic matter in the soil. The by-product is that wondeful dirt smell. Some soils smell like rotten eggs, thanks to other critters who thrive in an oxygen-poor environment. Under these conditions, these little bacteria start breaking down the sulphur in the soil, creating a nasty smell. Like everything else in the world of dirt, this is used as a tool to help classify and understand the soil and site. I know if I smell rotten eggs, that the soil is a wetland soil.

Below is a funky mess. This soil is on the edge of a large, glaciofluvial (Glacially-influenced river) delta. The soils comes from very fine glacial silts. That's why its that grey, I mean gley, color. It was a sunny day for this photo, but the bugs were hideous.




Sigh, I know I've bored you to bits but I LOVE what I do.

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