Rock Star GeoTours

07/31/2023

Saw some beautiful columnar joints at the Columns of the Giants on Hwy 108 (Sonora Pass) in the Sierras. Interesting feature! Had never been there before. Looks like 2 phases of cooling: maybe a lava lake followed by an irregular flow?

07/21/2023

Just one more day until Bodega Head Rocks! Join Rock Star GeoTours from 10am to 1pm at Bodega Head to learn about local geology, rocks, the San Andreas Fault, and the Hole in the Head. Hope to see you there! Learn more and register at

Ever wonder about local geology, the San Andreas Fault, and the Hole in the Head? Learn about rocks, faults, and California’s landscape.

07/07/2023

Two more weeks until Rock Star GeoTours has an outing at Bodega Head on Saturday, July 22! Learn about local Sonoma County geology, coastal erosion, the San Andreas Fault, and human creation of the Hole in the Head! Register at Eventbrite:

Eventbrite brings people together through live experiences. Discover events that match your passions, or create your own with online ticketing tools.

06/28/2023

Bodega Head Rocks! Saturday, July 22nd, from 10am to 1pm, join like-minded geo-nerds at the Bodega Head to learn about movement on the San Andreas Fault, the famous Hole in the Head, and Sonoma County's geologic history. Hosted by Rock Star GeoTours.

05/09/2023

This is just about right!

05/08/2023

Cave pearls in Carlsbad Cavern, New Mexico

Carlsbad Caverns National Park is a United States National Park in the Guadalupe Mountains of southeastern New Mexico. The primary attraction of the park is the show cave, Carlsbad Cavern.

The cave deposit, also called speleothem, any of the crystalline deposits that form in a solution cave after the creation of the cave itself. These deposits are generally composed of calcium carbonate dissolved from the surrounding limestone by groundwater. Carbon dioxide carried in the water is released as the water encounters the cave air; this reduces the water’s capacity to hold calcite in solution and causes the calcite to be deposited. These deposits may accumulate to form stalactites, stalagmites, flowstone, helictites, cave pearls, and many other formations. Deposits formed along ceiling cracks may produce drip curtains or draperies that may then reach the floor to become walls. Speleothems may grow in pools to form the nodular encrustations of cave coral or the natural dams that continually elevate themselves through accretion of calcite. The pure white of the calcium carbonate is often tinted with hues of red, yellow, and gray and may even be translucent. The growth rate of speleothems is highly variable due to seasonal variations in the rate of flow, carbon dioxide content, and other factors. Caves owe most of their beauty and much of their interest to these secondary growths.

05/08/2023

05/05/2023

Is this not amazing?!?! Columnar joints and a mid-ocean ridge make Iceland a spectacular geological playground.

Studlagil Canyon in Iceland 💚 💙
📷

05/01/2023

The Cedars Ecological Preserve is an otherworldly place to study geology, more closely resembling the surface of Mars than Earth. Largely made of serpentinite, there is ongoing active serpentinization happening at this location – on land, in Sonoma County! The serpentine soils are host to a whole community of plants that are endemic to just this piece of property. Enjoy a beautiful grotto with waterfall, various mineral pools, and epic views. The property is BLM land surrounded by private property, so the Cedars is not accessible without a pre-arranged tour.

Join Rock Star GeoTours on June 24th for an 8-hour geotour to and around the Cedars property led by naturalist Roger Raiche. For more information and to sign up, go to:

Discover unique natural beauty at the Cedars Ecological Preserve! Learn about geology, serpentinization, endemic plant ecology and more...

04/26/2023

Isn’t geology just amazing?

📸 Polished Moss Agate cab from Indonesia.
Credit Geology Wonders
Photo: Georgios Chatziparaskevas
NFS - Not For Sale.