Sonoma Land Trust hikes to explore Sonoma County geology

Sonoma Land Trust is offering a series of geological hikes that will take rock hounds over protected lands as well as the coastal Kortum Trail.

Geologist Glen Melosh will lead the series of three hikes over the weekend of Aug. 14 to 16. A free introductory talk Aug. 13, open to everyone, whether they attend the hikes or not, will cover basic geologic concepts and large-scale processes that result in geologic formations.

Participants can attend as many of the events as the choose, but are encouraged to take in the whole series, called “The Geology Transect of Sonoma County,” to get a fuller understanding of the county’s complex geology. A transect by definition is a straight line along which observations are made. The series aims to cultivate an understanding and appreciation of the geological processes that literally formed the bedrock of Sonoma County.

The weekend kicks off with the introductory talk from 7 a.m. to 8:30 p.m. in Santa Rosa.

On Friday August 14 the group will take an afternoon and evening hike, exploring Bodega Head, looking at the granite rocks on the Pacific plate, crossing over onto the North American plate for a walk down onto Shell Beach to see the Franciscan Formation and then venturing along the Kortum Trail to observe rocky outcrops that once served as scratching posts for giant mammoths. The 3 p.m. to 8 p.m. hike will include a picnic supper.

On August 15, hikers will visit the Harrison Grade Ecological Reserve to examine its serpentine rocks, then travel past Cazadero onto the land trust’s Ward Creek conservation easement property with its varied array of rock types. That hike will go from 9 a.m. to 3 p.m.

The land trust’s Live Oaks Ranch in Knights Valley is the destination for the final hike on Sunday Aug. 16. It will include a look at the volcanic rocks at the base of Mount St. Helena and an interpretation of the entire trip from a large-scale, earth’s crust point of view.

Melosh, a consulting geologist for Geothermal Geoscience, is interested in the fact that Sonoma County has so many geological formations compressed into a relatively small area.

“Sonoma County rock exposures reveal the powerful and dynamic processes that shaped the western U.S.,” he said in a release. “We

will build a vision of these processes across the county down to about 10 kilometers depth and over the last 150 million years. Over three days of hiking we’ll see pieces of the earth that have been scraped, slid, rolled erupted and flowed into place to build the county from the coast to the flank of Mount St. Helena.”

The introductory lecture is free. A $50 Sonoma Land Trust membership is required to attend any or all of the subsequent hikes, a $90 value. All field trip participants will receive a ‘Sonoma Geology” t-shirt.

For more information or to register visit sonomalandtrust.org or call 526-6930, ext. 110.

You can reach Staff Writer Meg McConahey at meg.mcconahey@pressdemocrat.com or 521-5204. On Twitter @megmcconahey.