A Forest Service geologist has been giving monthly talks about the geology of Grant County.
Seventy-four people packed into the St. Thomas Episcopal Church to see Hannah Grist’s presentation on the sedimentary rocks of the Aldrich Mountains March 8.
She explained a variety of deposition environments, ranging from glacial to oceanic, in which sedimentary rocks are formed.
Through crowd participation and examples, Grist revealed the Aldrich Mountains were formed by marine shoreline and offshore deposition processes. This is known based on the presence of chert-rich conglomerate, beach sand, marine shell fossils and marine microfossils, such as plankton and other small organisms.
“Sedimentary rocks are the great recyclers of the world,” Grist said.
The next talk, focusing on the granites of Dixie Butte, will be April 12. A field trip to explore fossils, chromium mines and stitching plutons is planned for a yet-to-be-decided date in May.
Grist said she started the talks after hearing observations, interpretations and questions about the geology from local miners.
She wants people who attend the talks to take away an understanding of local geology, allowing them to make observations and draw conclusions of their own while out recreating.
Grist said Grant County is an interesting place to study geology because there have been no lava flows to cover the process of accretion, the addition of material to a tectonic plate, which shaped the west coast. This has left the process that formed the region available to study.
Susan Church, the priest at St. Thomas, said she thought Grist was a great teacher and enjoyed the interactive portions of the lecture, especially the rock identification.
“It was wonderful to learn about the area I live in,” Church said.
She was grateful to learn more about the local geology and about how the Aldrich Mountains had formed. She expressed interest in seeing similar events on different topics and planned on attending next month’s meeting as well as the field trip in May.
For Church, it was also about building community. In the wake of recent divisive events, she said it was nice to be able to find common ground with other groups.
“It’s a way for people who hold different ideas and positions to come together and talk,” Church said.