Greenville HS Students Travel through Geologic Time
Geology rocks! Imagine getting into a time machine and traveling back over five hundred million years ago when the middle of Nevada was beachfront property. That’s what Greenville High School students from the Earth Science class did recently. They began the geologic journey near the Greenville “Y,” at the confluence of Indian and Spanish Creeks.
The fieldtrip was funded through a partnership with Plumas National Forest Storrie Fire Restoration project and the Plumas Unified School District (PUSD).
Rob Wade, Outdoor Education Coordinator for the PUSD, helped the students assemble the pieces of the geologic puzzle that make up the Feather River Canyon. Through the process of plate tectonics, the Pacific plate has been colliding and subducting under the North American plate for hundreds of millions of years. Picture two flimsy paper plates pushing against each other: one of them will give under the other; that’s subduction really simplified. Rock, mud, and earth build up layer after layer against the subduction zone creating a messy “parking lot” of geologic material.
If we dig through the layers of California, we would uncover a “big train wreck of rock pushing and pushing, heating and cooling, creating a pile-up of rocks.” Wade says the Feather River Canyon is more “fruitcake” geology that “layer cake.” The oldest rock can’t be counted on to be at the bottom.
Over time, the layers created four major belts observable in our Feather River Canyon. The Eastern Belt on this trip covered three formations, the Taylor, Arlington and Shoefly. From Shoefly Bridge, namesake of the formation, all the way to Rush Creek, students got an up-close look at the twists and turns of geologic history in all of its metamorphic glory. At the Paxton Ledge, near Paxton Lodge, the students saw evidence of rock laid down and pushed up, plate tectonics in motion! Over time mud at the bottom of the ocean becomes bedrock on the tops of mountains and then begins to erode only to head back toward the ocean again!
Near Rush Creek, students explored the Melones Fault, where the Eastern Belt gives way to the Feather River Peridotite Belt (four-hundred twenty million years ago). Eastern Belt metamorphic rock in the form of slate attracted the students to “slate-board” down a slope, while Feather River Belt serpentine and its related soil turned the Feather River Canyon into a place that plants seemed to avoid.
Continuing west to Rich Bar, the students encountered the Rich Fault, where gold was the most abundant in the canyon during the rush of the 1850’s. While noting the California Gold Rush, it was shared that the abundant serpentine that Serpentine Canyon is named for, is the California State Rock. Here, we transitioned to the Central Belt (largest belt of the Feather River Canyon). This transition zone was clearly defined on both sides of the canyon with sparse vegetation just to the east and a healthy forest zone to the west.
Onward into the Central Belt we stopped at Grizzly Dome, which is actually a granitic pluton. Once buried, the Feather River cut through and exposed this igneous rock. Here, where Grizzly Creek meets the North Fork of the Feather River, students saw bands or little intrusions of quartz transecting the pluton. Students even walked through a nearby cave cut through the solid pluton. Near the parked bus, they also found evidence of a ladybug hatch with thousands of reddish-orange sisters. Geologic time and ladybug time in all their glory!
The last stop near the Pulga Bridge revealed the emergence of the Western Belt that formed approximately one hundred sixty million years ago. The iron-rich rock gives the weather- exposed rock a reddish hue as our geologic journey in the Feather River Canyon came to an end. As we contemplated the end of the line for our Feather River Canyon geology study a student shared, “This is pretty cool, I never knew any of this!”
And yes, geology does R-O-C-K!