Geologic maps are 2D images that show the location and extent of geologic features like rock units and faults and are made of the surface or subsurface. Many geologic features such as faults and boundaries demarking rocks of differing ages and types are 3D surfaces within the earth, and a surface geologic map displays the intersection of the earth’s topography with these subsurface surfaces. Surface geologic maps are most commonly displayed over a topographic base, often colorful, are of considerable value to society and are commonly used in a variety of endeavors such as geologic hazard and risk evaluations, water management, dam safety, resource and land management, resource exploitation, environmental evaluations, and education. Subsurface maps, with the surfaces commonly displayed as depth below sea-level, are arguably the most important geologic tool in active fault evaluations, carbon sequestration, some environmental evaluations, water management, natural gas storage field siting and operations, oil and exploration and field operations, and mining.
A geologic cross section displays a side view of the earth. The configurations shown in a cross section are interpretive and there can multiple interpretations in area of complex geology. The best constrained cross sections utilize data from wells (oil & gas, water) and geophysical techniques such as seismic reflection.
Integrating geologic mapping and cross sections produces a 3D volume that is much better constrained and less interpretive than standalone maps and cross sections. These 3D geologic volumes are much easier to produce with recent developments in geologic and geophysical mapping software and more powerful workstations.
Our Objectives
The Geologic Maps Foundation (GMF) was founded in 2016 with the following objectives:
- Provide public education on geologic maps that includes the uses and benefits of these vital data sets and interpretations, plus teaching map reading and map making skills. Educational opportunities are provided through geo-hikes (for hikers and geologists), professional geologic field trips, and courses. These events are listed and open for RSVPs at https://www.meetup.com/Geo-hikes/
- Preservation of unpublished and out-of-print geologic maps, cross sections, and other geologic data and interpretations, and make available to the public, researchers, and policy makers via GMF’s web page library. There are now nearly three hundred geologic maps of southern and central California* in the library (a combination of mostly 7.5′ and 15′ quads) Maps are free to download and are high resolution .pdf files: https://geologicmapsfoundation.org/geologic-maps/. *Most of the original field mapping was done by Thomas W. Dibblee Jr. from the late 1930s to early 2000. Thomas L. Davis Geologist and staff digitized the original mapping in various GIS software over the last decade or more and we recently donated the .pdf copies to the Geologic Maps Foundation.
- Perform geologic research that deals with the world’s changing energy challenges and associated environmental questions.
It is widely recognized that more scientific outreach and STEM education is needed in our society. Maps offer a unique visual bridge to address this need. For millennia humans have combined their cognitive-spatial intelligence with graphics to create maps. Some researchers believe that maps may predate writing. Geologic maps add additional layers of information on the rocks and their structure that are displayed in a spatial manner. Information about the earth is relayed in a more universal manner that commonly relies more on symbols than text. With time a student will appreciate the earth-history story told by a map, further creating an interest in the earth sciences and potentially other scientific disciplines. More generally, map proficient students will learn a useful skill that broadens their knowledge of the outdoors and science.
Many adults, teens, and older children find geologic maps interesting and colorful even if they do not fully understand the information conveyed. Perhaps a map indicates the presence of gold and silver, even oil deposits, or an earthquake fault, but shown in some mysterious way only discernable to a trained geologist. By and large, the public do not appreciate the complete language of geologic maps that are standardized and easily taught to individuals over 7 or 8 years of age. Students of geologic maps learn more than how to read a map. They learn earth history, more about the science of geology and earth processes. Many geologic concepts rely on basic chemistry, physics and biology, and geology is widely recognized as a more qualitative means of broadly teaching STEM. This can be seen at many universities and colleges where introductory geology courses are very popular and commonly serve as the physical science requirement for liberal arts majors.
Additional educational accomplishments: GMF authored The Geology of Santa Cruz Island, California,
published by the Geologic Society of America: https://pubs.geoscienceworld.org/gsa/books/edited-volume/2279/chapter-abstract/126263829/Santa-Cruz-Island-field-trip-Geology-history-and
Every ridge, canyon, and desert plain tells a story written in the rock type and its
distribution beneath our feet. Geologic maps translate that story into color and pattern,
showing where ancient seas once spread, volcanoes erupted, and continents separated
and collided. For hikers, naturalists, mountain bikers, and anyone who loves exploring
the outdoors, these maps deepen the experience of being on the land.
Understanding the Landscape
Geologic maps reveal why a trail climbs steeply through limestone cliffs over one trail
section and winds gently through soft shale in another. They show how valleys form
along fault zones, why springs and stream flows emerge where permeable layers meet
impermeable ones, and why soils, vegetation, and wildlife differ from slope to slope.
Reading a geologic map transforms an ordinary hike into an exploration through time—
helping visitors connect what they see on the surface to the processes that shaped it
and it history.
How to use a Geologic Map
Geologic maps are beautiful but may look complex at first glance. Their layout follows
clear conventions. Generally, each color on the map represents the distribution of rocks
of similar type and age, aka unit, formation, member, bed, etc. On the legend or
explanation, the rock units are arranged from oldest at bottom to youngest at the top.
The rock units are separated by lines, often thin and black, where one rock unit meets
another. Geologists call these boundaries contacts. Thicker lines, sometimes green,
show the tract where folded rock layers meet the surface of the earth. The folds are
called anticlines if the oldest rocks are in the interior of fold or synclines if the youngest
rocks are in the interior of the fold. Even thicker lines, sometimes red, are faults, and
show the break where rocks or the surface of the earth have been displaced by
movement. All of the lines for contacts, folds, and faults can be solid, dashed, or dotted
depending on the certainty of location of the feature. Strike and dip symbols show the
compass orientation and tilt of layered rocks, mostly commonly sedimentary rocks.
Other specialized symbols show complex structure, mineral zones, volcanic features,
etc. and are defined in the explanation. Comparing the rock-unit map patterns and
various symbols, to what is in the field, it is possible to identify the rocks, folds, and
faults underfoot and visualize how they continue below the surface. A geologic map,
using colors, lines, and symbols, is a representation of the intersection of the landscape
and the geologic framework below the earth’s surface.
Before a hike, studying a geologic map helps identify areas of interest such as fault
zones, lava flows, or fossil-bearing beds. During a hike, it is useful to carry a printed or
digital map to match outcrops and formations to the mapped units. Afterward,
reviewing the map allows you to trace your route across time—seeing how you moved
through rocks that might span hundreds of millions of years. With practice, the colors
and symbols of a geologic map become as familiar as trail signs, offering a new way to
see and appreciate the land.
Safety and Awareness
Knowing the geologic layout also enhances safety outdoors. Trails that cross landslide-
prone slopes, areas susceptible to rock fault, fault scarps, mining areas, or volcanic
deposits can pose unique hazards. Geologic maps highlight such features, allowing
outdoor users, land managers, and even property owners to identify unstable terrain,
locate reliable water sources, and plan safe routes. Mining areas should be avoided and
entering mine shafts, abandoned and active, is very dangerous. For backcountry
travelers and search-and-rescue teams, understanding the terrain’s geologic framework
can be as critical as reading a topographic contour line.
Discovery and Appreciation
For naturalists and educators, geologic maps offer a guide and a colorful graphical
display of hidden treasures like fossil-bearing strata, mineralized veins, and striking rock
formations. Geologic maps encourage curiosity about a region’s geologic history,
evolution of the landscapes, and foster an understanding and respect for nature.
Mountain bikers tracing ridgelines or hikers standing atop mountain panorama will
appreciate that they are viewing the results of millions of years of Earth’s history.
Connecting Science and Recreation
Modern geologic maps, often available online or as smartphone layers, merge
seamlessly with GPS and trail apps. These digital tools allow outdoor enthusiasts to
overlay geology with trail networks, helping interpret what they see in real time. The
combination of recreation and science builds a deeper bond with nature—turning every
outing into a field trip through the planet’s evolving past.
There are now nearly three hundred geologic maps of southern and central California*
in the library (a combination of mostly 7.5′ & 15′ quads). Maps are free to download and
are high-resolution .pdf files: https://geologicmapsfoundation.org/geologic-maps/
*Most of the original field mapping was done by Thomas W. Dibblee Jr. from the late
1930s to early 2000. Thomas L. Davis Geologist and staff digitized the original mapping
in various GIS software over the last decade or more and we recently donated the .pdf
copies to the Foundation.
To date our operational costs have been funded by small donations from individuals and
field trips. For donations to our effort please use the following link: https://gofund.me/3579b963d
Focus
Geo-hikes is open to hikers, geologists and geology students.
It’s for anyone interested in learning a little geology while hiking and backpacking.
Visit Events\Calendar\Past on the Meetup page for the last few years for a quick appreciation, with photos, of Geo-hikes events,
Crooked Creek, White Mtns, https://www.meetup.com/https-www-meetup-com-geo-hikes/events/305325528 and https://www.meetup.com/https-www-meetup-com-geo-hikes/events/305488597
Santa Cruz Island, https://www.meetup.com/https-www-meetup-com-geo-hikes/events/306925451 and https://www.meetup.com/https-www-meetup-com-geo-hikes/events/306202687
Deep Canyon and Santa Rosa Mtns, https://www.meetup.com/https-www-meetup-com-geo-hikes/events/306197727
Mojave National Preserve, https://www.meetup.com/https-www-meetup-com-geo-hikes/events/306976854
Hikers, do you want to learn a bit of field geology and map reading skills while hiking, and sometimes camping in the western USA? Interested in participating in Geo-hikes and trips to scenic, and sometimes remote, locations? Want to learn about the fascinating history of the earth at these locations while on the move? If yes, then events hosted and led by the Geologic Maps Foundation might be of interest to you. Plus, the participants meet others with similar interests while getting great exercise. You do not have to be a geologist to attend but an eagerness to learn some basic geology and map reading skills are a must.
Professional geologists can share their knowledge and experiences (as co-leaders) with geology students and non-geologists while exercising and returning to, for many, why they got into geology in the first place.
Geology students (at any level) will gain field experience, an opportunity to interact and make contacts with professional geologists that could be helpful in the future, and with lots of outdoor exercise in interesting geologic settings.
There are a number of geo-hikes scheduled for the 2023 season and more will be added. “Spreading the word” about these events is most appreciated. Interaction of professional geologists and geology students with hikers, that are not geologists, informs the public about geology and its importance.
Geo-hikes also organize and lead customized geologic field trips for professional organizations and companies to various areas in the western US and Baja California. Trips are great educational and team building experiences. Please email us at: geologicmapsfoundation@gmail.
Our Objectives
The Geologic Maps Foundation (GMF) was founded in 2016 with the following objectives:
- Provide public education on geologic maps that includes the uses and benefits of these vital data sets and interpretations, plus teaching map reading and map making skills. Educational opportunities are provided through geo-hikes (for hikers and geologists), professional geologic field trips, and courses. These events are listed and open for RSVPs at: https://www.meetup.com/Geo-hikes/
- Preservation of unpublished and out-of-print geologic maps, cross sections, and other geologic data and interpretations, and make available to the public, researchers, and policy makers via GMF’s web page: see Library pull down menu at: https://geologicmapsfoundation.org/library/.
It is widely recognized that more scientific outreach and STEM education is needed in our society. Maps offer a unique visual bridge to address this need. For millennia humans have combined their cognitive-spatial intelligence with graphics to create maps. Some researchers believe that maps may predate writing. Geologic maps add additional layers of information on the rocks and their structure that are displayed in a spatial manner. Information about the earth is relayed in a more universal manner that commonly relies more on symbols than text. With time a student will appreciate the earth-history story told by a map, further creating an interest in the earth sciences and potentially other scientific disciplines. More generally, map proficient students will learn a useful skill that broadens their knowledge of the outdoors and science.
Many adults, teens, and older children find geologic maps interesting and colorful even if they do not fully understand the information conveyed. Perhaps a map indicates the presence of gold and silver, even oil deposits, or an earthquake fault, but shown in some mysterious way only discernable to a trained geologist. By and large, the public do not appreciate the complete language of geologic maps that are standardized and easily taught to individuals over 7 or 8 years of age. Students of geologic maps learn more than how to read a map. They learn earth history, more about the science of geology and earth processes. Many geologic concepts rely on basic chemistry, physics and biology, and geology is widely recognized as a more qualitative means of broadly teaching STEM. This can be seen at many universities and colleges where introductory geology courses are very popular and commonly serve as the physical science requirement for liberal arts majors.
Additional educational accomplishments: GMF authored The Geology of Santa Cruz Island, California, published by the Geologic Society of America: https://pubs.geoscienceworld.org/gsa/books/edited-volume/2279/chapter-abstract/126263829/Santa-Cruz-Island-field-trip-Geology-history-and
Board of Directors
Thomas L. Davis, PhD, President and Director. California Professional Geologist #4171
Davis is a California State registered geologist and an author on a number of geologic publications-especially dealing with the structural geology and petroleum potential of California. Davis has worked as a consultant and researcher worldwide, for numerous public and private energy companies, several national oil companies, the United States Geological Survey (USGS), Southern California Gas Company, and the Playa Vista development in the Los Angeles basin. Formerly Davis was a partner in Davis & Namson Consulting Geologists, and prior worked for the Atlantic-Richfield Corporation.
David Kimbrough, PhD, Vice-President and Director. Professor of Geology, California State University San Diego
Dr. Kimbrough completed his PhD at UCSB (on geology of Cedros Island, Baja California) and served as a SDSU faculty member since 1989. He has led research and education efforts in the circum-Pacific region (Antarctica, New Zealand, Australia, Japan, Canada, Mexico, South America) supported mainly by NSF grants.
Adam Wolf, Esq., Director. Peiffer, Rosca, Wolf, Abdullah, Carr & Kane, A Professional Law Corporation
Adam is an attorney and a Shareholder in the law firm Peiffer Wolf Carr Kane Conway & Wise, LLP. He handles complex civil lawsuits, litigates constitutional and civil rights claims, and represents clients in appeals. Adam has argued in the United States Supreme Court, in addition to numerous federal and state courts of appeals.
Monica Davis, MBA, Treasurer and Director. Chief Operating Officer of Mental Health America of Los Angeles (MHALA)
Monica Davis, MBA is the Chief Administrative and Contracts Officer for Mental Health America of Los Angeles. She has spent 20+ years working in the public mental health system, performing roles of outcomes collection and analysis, business operations, finance, and county contracting. From 2001 – 2007, Monica was the coordinator of the department that collected, analyzed, and reported the statewide data that was used to advocate for the Mental Health Services Act.
Lindsey Hronek, Secretary and Director. PhD Student West Virginia University
Lindsey Hronek has worked at Thomas L. Davis Geologist for ten years doing administration, book-keeping, drafting, and GIS assignments. Lindsey is also working on her PhD in Behavior Analysis at the West Virginia University.
The Geologic Maps Foundation, Inc. (GMF) is a tax-exempt nonprofit, IRS 501 (3) (C), with a scientific educational and research focus. Donations are tax deductible and pay for GMF and Geo-hikes event expenses and operating costs.