Welcome to the Cal Geographic Report – We look forward to sharing news and updates of the biogeography and physical geography of California’s living landscapes ~
Topics on this episode include expanded protections for White sharks, a significant earthquake on the Maacama fracture zone, the history of California’s geographic surveys from the peak of Mount Diablo, a rundown of our upcoming field trips, and more ~
Links and citations to the topics covered on the Cal Geographic Report podcasts can be found in the episode transcripts at Cal Geographic.com.
Thanks for tuning in, and please consider supporting our work at Cal Geographic so we can continue to share the geography of California’s living landscapes. Your contribution directly supports our research, reporting, and educational outreach.
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We are excited to announce our upcoming field trips and events for this summer and fall:
Please visit our Field Trips and Events page on Cal Geographic to register, for complete logistical information, and for updated events as they are scheduled:
On Friday, July 24, 2026, we are co-leading, Point Arena’s Coastal Geomorphology, Marine Terrace Evolution, and Ecosystems
Don’t miss Part Two of our successful field trip in June to Point Arena’s Stornetta Lands, co-led with the Bureau of Land Management ecology and wildlife staff. Please join us to view and discuss coastal geomorphology and tectonics, and the rare native ecosystems of Point Arena.
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On Saturday, September 12th, 2026, we are leading the field trip, Tectonics, Geomorphology, and Living Landscapes of Little Lake Valley on the Maacama Fracture Zone
This field day will be at the Willits Bypass Mitigation Lands, and in partnership with the Mendocino County Natural Resource Conservation District.
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On Tuesday, September 15th, 2026 at 7:00 pm, I will be giving an evening presentation, The Mighty Maacama: Tectonic Fracture Zone and Primary Plate Boundary,
At the Ukiah Civic Center (City Council Chambers), 300 Seminary Drive, in Ukiah, 7:00pm
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And on two Sundays: September 27th, 2026 and October 10th, 2026, from 10:00 am until Noon, Cal Geographic will be leading, Coastal Landforms and the Tectonic Landscape at the Mendocino Coast Botanical Gardens
We will explore the western edges of the Mendocino Coast Botanical Gardens to discuss and marvel at northern California’s coastal landscape and landforms. We will observe local geology, and explore the evolution of coastal landforms including marine terraces, the tectonic forces and mechanisms that are shaping the landscape, and the interplay between coastal geography and the native ecosystems adapted to it.
Cal Geographic Field Trips and Events Page
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The California Department of Fish and Wildlife is calling for information to aid in the recovery planning for Milo Baker’s lupine and Surf thistle under the California Endangered Species Act
Surf thistle (Cirsium rhothophilum) will undergo a five-year species review to determine if the conditions that led to its original listing of threatened under the California Endangered Species Act have changed, to provide recommendations regarding the species’ status and management to the California Fish and Game Commission, and to collect any information that will further recovery planning for this species.
Milo Baker’s lupine (Lupinus milobakeri) recently underwent a five-year species review and a status review by the Department with a recommendation of a listing status change from threatened to endangered. The Commission subsequently determined that a change in listing was warranted and listed Milo Baker’s lupine as endangered under California Endangered Speceis Act. We are seeking any additional information or opportunities for collaboration with interested parties that will further recovery planning for this species.
Surf thistle is a low-growing, short-lived perennial thistle that occurs on coastal dunes from Pismo Beach to Santa Barbara, occurring in San Luis Obispo and Santa Barbara counties. Milo Baker’s lupine is a tall, annual lupine that occurs in Round Valley in Mendocino County.
Take of these species is prohibited without the appropriate permits, including for scientific, educational, or management purposes.
As part of this process, the California Natural Diversity Database encourages anyone who has observed Surf thistle or Milo Baker’s lupine to submit their findings through the CNDDB Online Field Survey Form.
Questions or comments about the recovery planning process can be sent to CESArecovery@wildlife.ca.gov with the species name in the subject line. The deadline to submit information or comments is September 30, 2026, to allow sufficient time for evaluation.
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Earthquake on the Maacama Fracture Zone
For several months now my research and writing has been laser focused on the complex and intriguing setting of the Maacama fracture zone in Sonoma and Mendocino Counties, and on the morning of June 24th I had just sat down to wrap up the final edits of a presentation on the mighty Maacama that I will be giving this summer in Ukiah, when a robust earthquake released from a major strand of the Maacama fracture zone.
The June 24th Redwood Valley earthquake not only shook close to home and coincidentally occurred within a tectonic setting that I’ve been professionally consumed by, but it was also a rare tectonic event within this fracture zone, measuring at magnitude 5.6, and believed to be the largest earthquake occurring on the Maacama that is recorded in the USGS catalog.
The main shock of the June 24th’s earthquake appears to have emanated from the eastern bifurcated arm of the Maacama fault within the Redwood Valley strands, along Tomki Road. Unfortunately, the epicenter was within a rural residential area, and directly adjacent to a Buddhist Monastery in upper Redwood Valley. Within the first six hours following the magnitude 5.6 earthquake, there were at least 35 aftershocks over magnitude 1.3.
The Maacama Fracture Zone is a splintered network of fault strands branching out at angles from and semi-parallel to the mainstem of the Maacama fault. The Maacama system is so fractured that the vast majority of fault strands associated with it have yet to be identified, and
swarms of small earthquakes and interlocking faults along the fracture zone can be so numerous that they form what is known as a mesh, or a fracture mesh
In 2021, renewed investigations of the northern Maacama’s tectonic geomorphology revealed several new and active fault strands splintering up through Redwood Valley. The June 24th, 2026 5.6 magnitude earthquake and aftershocks occurred just north of these newly identified strands, which will undoubtedly instigate the identification of yet more fault strands extending up Redwood Valley and within the Maacama fracture zone.
For further information on the June 24th Mendocino county earthquake, and the tectonics of the Maacama fracture zone please read our articles and references posted on Cal Geographic.com, and linked to the transcript for this podcast.
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The following are excerpts from the Finding of Emergency Statement and the Proposed Emergency Action from the California Fish and Game Commission, with regard to Recreational Gear Restrictions for White Sharks, as of June 18, 2026
Statement of Facts Constituting the Need for Emergency Regulatory Action –
Background on the issue:
White sharks (Carcharodon carcharias) are an important apex predator in the marine ecosystem, and are protected under state and federal fishing regulations. There have been several recent incidents involving pier and beach anglers either intentionally targeting white sharks, or accidentally hooking them with very heavy fishing gear. These incidents have resulted in the death of at least three white sharks this year. Additionally, in 2014, a swimmer was bitten by a white shark that had been hooked by a pier angler.
This year, a forecasted strong El Niño oceanic event is anticipated to increase the presence of white sharks in California coastal waters, which will increase their availability to anglers and the potential for human interactions with hooked sharks. Young white sharks are already being observed in significantly higher numbers in southern California. Because of this, there is an immediate need to curtail illegal targeted fishing for white sharks, help ensure accidentally hooked sharks are released alive, and help prevent another incident where a hooked shark bites an ocean user, or the heavy gear used to catch such sharks entangles a person in the water.
Proposed Emergency Regulations:
Proposed amendments would require that any white sharks that are caught be released immediately, and would prohibit removing white sharks from the water. These changes are necessary to improve the chances for white sharks to survive following release after being hooked incidentally, and to reduce the risk of injuries to people who might attempt to handle or lift the white sharks out of the water.
Proposed amendments would prohibit the use of wire or metallic lines or leaders, as well as hooks greater than one and one-half inches in maximum inside measurement, when fishing in ocean waters south of Pigeon Point (San Mateo County, 37° 11′ N. lat.). This restriction would apply to anglers fishing from the shoreline (including beaches, banks, piers, jetties, breakwaters, docks, and other man-made structures connected to the shore) or within 1,000 yards of the mean high tide line.
These changes are necessary to better protect white sharks from illegal targeting, allow incidentally hooked white sharks to more easily break free from the line, and prevent sharks from being released with trailing wires that can entangle the shark after release.
The proposed boundary is set south of Pigeon Point because aggregations of juvenile white sharks have not previously been observed north of Santa Cruz, and Pigeon Point is an established, easily identifiable, geographical management line.
Findings for the Existence of an Emergency:
The Fish and Game Commission considered the following factors in determining that an emergency currently exists. The Department has indicated that increased shark aggressions are occurring in Southern California Waters this year. Juvenile white sharks usually move into Southern California waters in the summer months, as waters to the south become too warm. During warm water events, the sharks are present in greater numbers and are present farther north.
The National Oceanic and Atmospheric Administration (NOAA) is forecasting a strong El Niño event, beginning this summer that will bring warmer than normal waters to the California coast. These warm water events have historically led to increased presence of white sharks in California, and a northward shift in the range of juvenile white sharks. In early April 2026, 20 juvenile white sharks were caught in a single day from the Hermosa Beach Pier. Additionally, at least three white sharks have been documented to have died this year after being hooked and released with heavy fishing gear consisting of wire leaders and large hooks.
The magnitude of potential harm:
As white shark presence is expected to increase during the summer months, it is likely that dozens of sharks could be killed through incidental and illegal targeted fishing activities over the course of the year. This could have a substantial negative impact on white shark populations.
The existence of a crisis situation:
No white sharks (Carcharodon carcharias) are allowed to be taken recreationally, as they are an important apex predator in the marine ecosystem and are protected under state and federal fishing regulations. White sharks are slow-growing, long lived, and have low reproductive rates compared to other fish species. As a top-level predator, healthy populations are necessary to maintain a balanced ecosystem.
Benefits of the Regulation:
The Commission anticipates benefits to the State’s environment by sustainably managing California’s ocean resources by limiting the potential increase of white shark take. The Commission also anticipates improved public safety, by reducing the chance that an incidentally hooked shark remains on the line and either bites someone in the water or injures a person with a trailing wire leader.
The Commission conducted an evaluation of existing regulations, and this regulation is neither inconsistent nor incompatible with existing state regulations.
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California State Parks, in partnership with the Mount Diablo Surveyors Historical Society and the Mount Diablo Interpretive Association, invites the public to celebrate the 175th anniversary of the Mount Diablo Initial Point Meridian on Saturday, July 18, from 10 a.m. to 4 p.m. at the summit of Mount Diablo State Park.
Established in 1851, the Mount Diablo Initial Point and meridian became the reference point for surveying property boundaries across much of California and all of Nevada. The Initial Point played a critical role in mapping land ownership during California’s early development and continues to serve as the foundation for property surveys throughout the region today.
The celebration will feature demonstrations of antique and modern surveying equipment, hands-on activities, informational exhibits, and guided tours highlighting the original survey monuments housed inside the Summit Visitor Center. Land surveyors and historians will also be available to answer questions and share the history and significance of the Initial Point.
Visitors can learn about California’s land surveying history while taking in spectacular views from the summit of Mount Diablo, stretching from the Farallon Islands to the west, across the Central Valley and to the Sierra Nevada to the east.
For directions and logistics, please check the Mount Diablo Interpretive Association website: https://www.mdia.org/event-details/175th-anniversary-of-mount-diablo-initial-point-1
Here’s a word from Cal Geographic:
I would just like to reflect, that while this is a worthy event offering a tangible and unique exploration of California’s historic and significant geographic surveys, and at a very cool geographic and geologic location, it is also important to consider that the history of land surveying for the purpose of property acquisition and settlement has led to the destruction of much of California’s native landscapes and natural resources. So, for me it’s another quandary, or oppositional relationship between California’s historic (human) geography and the study of our state’s physical geography.
Here’s a little bit about the physiography of Mount Diablo:
Mount Diablo is a young tectonic landform and is very young for a mountain of almost 4000 foot elevation. For two million years, Mount Diablo has been compressed, uplifted, and transported by the Mount Diablo blind thrust, which is warping and deforming the earth’s crust as it takes up transpressional forces and energy of some of the major neighboring transform faults including the Greenville, Franklin Canyon, Concord, and Calaveras faults. Mount Diablo is a prime specimen of Coast Range tectonic geology and geomorphology – constructed of uplifted Franciscan formation and ophiolite components of the Farallon plate subduction complex, and rimmed by younger sedimentary rock units that display intriguing characteristic erosional landforms such as tafoni, concretions, hogback ridgelines, and fossil beds. So enjoy the geologic environment and tectonic geomorphic spectacle that is Mount Diablo if you travel to the summit for the 175th anniversary of the survey point and meridian.
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Thank you for listening – You can find citations, links, and references for the topics covered in this episode of the Cal Geographic Report on our website – CalGeographic.com. We look forward to further explorations and investigations of the biogeography and geomorphology of California’s Living Landscapes
