SDAG monthly meeting
Thursday - November 20 |
Location:
The Old Spaghetti Factory
111 North Twin Oaks Valley Road
San Marcos, CA 92069
(760) 471-0155
Directions:
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6:00pm -
Social hour
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SDAG and AEG-IE Joint Meeting
6:00pm - Social Hour
7:00pm - Dinner
8:00pm - Program
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7:00pm
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Menu: Italian Buffet (includes Meat sauce, Mizithra, Fettuccine, and vegetarian options) includes salad, bread & spumoni ice cream
if pre-registered by the deadline, $5 extra if you did not make a reservation.
Click the SDAG member checkbox on the reservation form if you are a member.
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Cost: $ 45.00 Member; Non-Member $ 55.00; Student $ 20.00
Reservations:
Make/Pay your reservation online by clicking the button below
by 6:00pm Monday, November 17
RESERVATIONS CANNOT BE ACCEPTED AFTER by 6pm Monday, November 17
(Please note beginning January 2024 all meeting reservations will require on-line pre-payment due to venue costs,
venue contracts, and loss of money due to no shows.)
IF YOU DO NOT PRE-PAY YOUR FOOD RESERVATION, WE CANNOT GUARANTEE YOU A MEAL.
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8:00pm - Program
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"San Joaquin Hills, Santa Ana Mountains, Puente Hills, and the Whittier fault: The final(?) grand theory of Orange County's tectonic geomorphic evolution"
Speaker: Eldon Gath, Senior Consultant of Earth Consultants International
As my home, it has always puzzled me by how unstudied Orange County really has been. Sure there are geologic maps, and we can see the geomorphology out there,
but do we really understand it? And why not? Hence my decades (career) long effort to generate that understanding and communicate it to others as best I can.
This was never a solitary effort, there are too many to name who have helped in many ways: trench scraping, field trips, discussions, suggestions, and sometimes
laughter. To them I am deeply appreciative, but any errant conclusions within this talk are not their fault.
Orange County California is home to over 3 million people making it the sixth densest county in the U.S. From its high point atop Santiago Peak it is 5,689 ft
(1,734 m) down to the coastline at Laguna Beach, a distance just shy of 100,000 feet (30,000 m). The San Juaquin Hills at (height) and Puente Hills at (height)
bound the west and northern county. But at 3 Ma, none of this expensive real estate yet existed; Orange County was part of the Pacific Ocean. This talk will
try to explain how this came to be, by starting the clock at 3 Ma and ticking our way up to today.
The Santa Ana Mountains are an indenter (think hydraulic piston) driving northwesterly at ~6 mm/yr by the Elsinore fault. As they close the basin, the entire
Cretaceous - Pliocene sedimentary section is folded, faulted and piled onto the front of the indenter. Meanwhile the Puente Hills thrust forms in response to
north-south compression against the San Gabriel Mountains. As the compression tightens by 1 Ma, other structures begin to emerge as transpressional folds and
faults; the San Joaquin Hills and the Peralta Hills, while the Whittier fault accommodates about 3 mm/yr of right-lateral strain as the basin slides out to t
he west.
Today, the indenter is in full train-wreck mode as it completes the collision with the Puente Hills in Santa Ana Canyon. We can see this expressed in both the
geology and geomorphology of the Canyon. As that collision has tightened, the uplift rate of the Puente Hills has tripled to ~3 mm/yr today. Today we see
extensive landsliding in the Canyon area due to that jump in uplift rates for already crushed and seismically weakened Puente Formation rocks, as well as
hundreds of small faults, fractures and folds any of which could be candidates to accommodate (minor) deformation in a future earthquake. Orange County is
a happening place.
Eldon Gath is President and Senior Consultant of Earth Consultants International since founding the company in 1997. As a consultant he has worked on projects
in Turkey, Panama, Costa Rica, Taiwan, Japan, Mexico, Papua New Guinea and hundreds in California. He is also a Past-President (1987) of the South Coast
Geological Society (SCGS), an Honorary Member (2012) and currently serves as the SCGS Board Treasurer. He was President (1996-1997) of the Association of
Environmental and Engineering Geologists (AEG) and U.S. National Group Leader (2014-2018) and North American Vice-President (2017-2018) of the International
Association for Engineering Geology and the Environment (IAEG). In 2014-2015 he was the AEG/Geological Society of America’s (GSA) Richard H. Jahns Distinguished
Lecturer in Applied Geology. Along the way he has acquired other notable distinctions such as outstanding paper awards (2010 Burwell from GSA & 2012 Holdredge
from AEG), outstanding presentation awards (1995 Aki from S.C. Academy of Sciences and 2008 Hanson from American Association of Petroleum Geologists (AAPG)),
Johnston Service award from AEG (2008), GSA Fellow (2011), and others from the National Academy of Sciences, American Geological Institute, and the European
Geosciences Union. To date, he has 56 published papers, co-edited 7 SCGS Field Trip Guidebooks, has presented 61 times at professional conferences, and 230+
times at schools, professional societies, and community meetings.
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Upcoming SDAG meetings - 2025
November 19 - Joint Meeting with AEG Inland Empire Section - Eldon Gath on "San Joaquin Hills, Santa Ana Mountains, Puente Hills, and the Whittier fault: The final(?) grand theory of Orange County's tectonic geomorphic evolution" - Old Spaghetti Factory, San Marcos
December 17 - Traditional Holiday Celebration at the San Diego Natural History Museum with Tom Deméré on "150 years of Paleontology at the San Diego Natural History Museum"
Recordings of past meetings
Note: If the video or sound does not play, try using another web browser. Firefox and Chrome may work on some of the videos. MS Edge and Safari are most likely to work.
10/15/2025 Todd Wirths on "Eocene Paleontology at Tourmaline Surfing Park, La Jolla"
8/20/2025 Dr. Mario Caputo on "Newly Discovered Tetrapod Bones, Insect Trace Fossils, & Eolian Adhesion Structures- Upper Pennsylvanian Wescogame Formation, Supai Group, Grand Canyon, Arizona"
7/16/2025 Rachel Maxwell on a survey of the Mojave-Sonoran Desert Springs and their sources. "Is this spring connected to that Aquifer?"
6/18/2025 Development of the western Hollywood Basin and Cheviot Hills, and newly identified blind thrust in Santa Monica Bay - Dr. Miles Kenney
5/14/2025 Landslide Stabilization - Dr. Sebastian Lobo-Guerrero (Audio is very quiet first few minutes.)
4/16/2025 Constraining Natural and Anthropogenic Controls on Base of Freshwater and Underground Source of Drinking Water (USDW) In Central San Joaquin Valley - Emily Imperato
4/16/2025 Examination of Middle Cambrian hyoliths from the Manuels River Formation of Avalonian southeastern Newfoundland - Nicolas Oliver
2/19/2025 A New Seismotectonic Framework for Active Faults in Metropolitan San Diego - Karl Mueller
8/21/2024 Upper Cretaceous through lower Eocene strata in San Diego: Messages for the end-Cretaceous impact, extinctions, and paleoclimates - Dr. Pat Abbott
5/15/2024 Exploring Iceland's Geological Wonders: From a Regional Perspective to a Hiking Expedition - Don Barrie & William Buckley
3/19/2024 Mighty Bad Land: A Perilous Expedition to Antarctica Reveals Clues to an Eighth Continent - Bruce Luyendyk
Meetings are usually scheduled for the 3rd Wednesday evening of the month.
Meeting information on this website is normally updated the second week of the month.
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The submittal deadline for the next SDAG newsletter is the last Friday of the month.
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