Western Meadowlark in the Volcanic Barrens of the Sierra Nevada Foothills

The western foothills of the Sierra Nevada are one of the least-known parts of the range. Every year, millions of tourists drive quickly through the grasslands on their way to Yosemite Valley or the recreational lakes towards Sonora Pass. They pay little heed to the barren landscape, but in so doing they are missing out on one of the most dramatic parts of the geological story of the Sierra Nevada.

Nine or ten million years ago, the Sierra Nevada was a different place. The range was lower, and Cascades-style volcanoes were active in the summit regions around Sonora and Ebbets Passes. There may not have been large-scale glaciers, but the volcanoes may have been covered with snow at times, and erupting ash would have produced volcanic mudflows (lahars) that traveled dozens of miles down the western slopes. The mudflows came to rest in the foothills where today the deposits are called the Mehrten Formation.

In some circumstances, the volcanic muds could produce rich soils, but yearly rainfall is only enough for prairie grasses to grow. It's not a desert, but it's not a woodland either. The grasslands do provide excellent habitat for the Western Meadowlark (Sturnella neglecta), and it's a rare trip when I don't see one in the area. These pictures are from a short excursion a week or two ago on Willms Road near Knights Ferry on the Stanislaus River. One can just make out the bird on the rocks in the foreground of the first picture, but zooming in I got a better view. I love the colors of the lichens on the rocks.