Geologic History of San Diego County: Recap of Don Albright’s Talk
By Jeanie Anderson
Did you ever pick up a rock and ponder where it came from and how it was formed? Did you ask yourselfwhat your backyard looked like millions of years ago? How did Black Mountain happen? Did you know that we are on a plate called the Pacific Plate along with Baja California – moving northwest and away from the North American Plate?
Geology seeks to discover answers to these questions through a sort of forensic analysis to piece together the equivalent of a crime scene -- chronologically – essentially how did the now happen from the past and where are we headed in the future.
Well, on Saturday Sept. 14 th , we were treated to a fascinating presentation by our own Geologist and co- founder of the Friends of Los Penasquitos Canyon Preserve, Don Albright. Don is a native of San Diego County, growing up in Chula Vista and later Mission Beach. His early passion for geology drove him to academic studies, where he became the first San Diego State University student to graduate with a Geology Degree in 1956.
Don sharing a Rock Pick with Jeanie
Don’s presentation, The Geologic History of San Diego County, featured a slide deck of geologic epochs, hand colorized to represent geologic rock types and zones. It was created for his long-time program at the San Diego Museum of Natural History where he was part of the geology department, teaching the public about our unique geologic history. Please note, The Friends will publish Don’s presentation online soon. Because it is a challenge to wrap our heads around millions of years of time, 2 handouts on geologic time scales are provided, one from the late Proterozoic to Cenozoic (650 – 2.6 million years) and the other providing the Cenozoic Epochs from 65.5 million years ago to today. Stay tuned!
Below is one of the slides representing the middle Miocene - 20 MYBP – Million Years Before Present.
Don shared the story of the February 1956 earthquake – magnitude 6.8 -- which occurred while he was a senior at SDSU. Because there was no GPS or satellite tracking, he and fellow students used seismometer data from 3 locations to interpolate the location of the earthquake – which revealed the location to be in the mountains east of Ensenada Mexico in the Ojos Negros area. They launched an expedition in the springtime and did indeed discover the earthquake fault, standing in the large crack to experience it first-hand!
In addition to the slides, Don shared a vast collection of rock types, explaining them in detail. Folks got to handle them as well, a great way to learn. Thank you to the team for carrying the rocks from Don’s van to the Ranch House - a heavy lift.
Don showing a rock to the crowd
We learned so much about geological processes – for example, how when magma cools deep in the earth it creates granite batholiths. We learned that Black Mountain is comprised of a mineral known as Andesite – named after the Andes Mountains.
In conclusion, we thank Don Albright for all his time and insightful stories about the fascinating geologic history of San Diego County. We invite all of you to view and listen to this thru our website, once it is posted in our video section.
The study of geology can be all encompassing or start with the rocks in your area. Whichever direction you take, please remember not to take it for granite!
It was my pleasure to assist with this presentation, learning so much from our local rock star, Don Albright.
Additional Resources
Video: A Hike Through Geologic Time ~ The Geology of Los Penasquitos Canyon
Join geologist, Don Albright, for a virtual hike thru Geologic Time. From the mesa rim rocks of the Linda Vista Formation to the andesite volcanic bedrocks at the Waterfall on the canyon floor, Penasquitos Canyon spans 150 million years. Along the way, you will learn about vernal pools, mima mounds, the little cliffs that give Penasquitos its name, and much more. Video is 6 minutes in length.
Book: The Rise and Fall of San Diego: 150 Million Years of History Recorded in Sedimentary Rocks (Sunbelt Natural History Guides) by Pat Abbott
https://sunbeltpublications.com/shop/rise-and-fall-of-san-diego/
For reference, you can go to this website for more info on Geological Resources for San Diego County & Southern California:
