The science that Garry Hayes loves isn’t made up of esoteric polynomial equations or invisible dark matter. It’s as solid as the rocks he climbs on and as visual as the stunning photographs he posts on his geology blog, Geotripper.

Hayes, who teaches geology at California’s Modesto Junior College, just came back from an off-the-grid trek through the Sierra Nevada mountains, in the eastern part of the state, and he’s posting photographs of his trip accompanied by the story of how the peaks and valleys came to look the way they do. They pretty much make you want to be a geologist.

You see the vast plain near Owens River Gorge, for example, where a massive volcanic eruption “put 150 cubic miles of hot ash into the atmosphere 760,000 years ago, blanketing the entire American West.” The eruption, he says, caused the crust to collapse into a 20-by-11-mile hole that subsequently filled with the layers of earth Hayes photographs from the plain’s eastern boundary.

On a trip to British Columbia this month, he posted images from “the ancestral edge of the North American continent,” now 600 miles inland. Some 400 million to 900 million years ago, he writes, limestone and other sediments from across the Pacific were deposited to create the cliffs above the Kicking Horse River — where finely ground pale clay in the turbulent water can make the river look like “flowing milk.”

Hayes give geology a sense of dramatic immediacy, and his blog is jampacked with links to other lively sites: on mining history, science radio, volcano webcams and (students, take note!) “geotripper images” in case you “need a geology-themed image for a report or paper.”