Geology is a critical component of agriculture. The recessional glacial outwash plains around Lynden in northwest Washington formed some of the best agricultural lands in western Washington. The narrow gap at Wallula in the Horse Heaven Hills backed up ice age flood waters which in turn filled the Yakima and Walla Walla valleys with thick blankets of silt (lake-lewis-and-wallula).
I had a nice geology outing with a soil scientist last week. It was informative interaction and we were traversing through country where Jay had completed soil mapping projects. Jay noted subtle features in the soil I would never have noticed without him.
Note tiny tan grains
The small grains in the soil are tiny pieces of volcanic tephra. Given the central Washington location and the distribution of the grains Jay described, the source of the tephra is likely from Glacier Peak (Porter, 1978 and Kuehn and others, 2009).
(Kuehn and others, 2009)
This seeming small feature is a big deal to the local agricultural productivity. The tephra fragments allow the soil to hold a lot more moisture and thus adds significantly to the productivity of the fields where the volcanic material is present. The various tephra deposits are an important dating tool and thus tephra deposits are of great interest to more than geologists. Glacier Peak had a particularly violent eruptive period during and after the last glacial period. Mount Saint Helens and Mount Mazama also deposit tephra over a large areas. The three volcanoes have left dating markers over wide swaths of teh northwest.
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