12.8: Detailed Figure Descriptions

Intro Image

An image of the Geomorphic Provinces of California with the Great Valley highlighted. The Great Valley is highlighted in the center of the image, which represents the central portion of California and runs up and down the image (truly north and south) and covers approximately 11% of California’s land mass.

Figure 12.2.1: Paleogeography of the Great Valley during the Middle Miocene

This image is a geological map highlighting tectonic activities during the Middle Miocene period, approximately 20 to 15 million years ago. The map shows the western coast of North America, including parts of present-day California and Baja California, with various geological features and tectonic movements labeled and indicated with arrows. Key elements and annotations on the map include the initiation of the Mendocino Triple Junction located off the northern coast of California, indicated by a blue arrow pointing to a yellow line representing the plate boundary; the initiation of strike-slip motion, indicated by another blue arrow pointing towards the southern part of California where the San Andreas Fault is located; the rotation of the Transform Ranges Microplate, shown with a blue arrow pointing to the southeastern region indicating the microplate's rotation; and the rift valley formation, highlighted with a blue arrow pointing towards the lower right of the map, showing the beginning of a rift valley formation along the Baja California region.

The map also shows various tectonic features such as subduction zones depicted in yellow, transform faults depicted in red and blue lines, volcanic arcs and basins marked with purple text, and block rotation and rift formation indicated with green and blue lines. The overall image presents a detailed view of the tectonic activities and geological changes during the Middle Miocene, with significant emphasis on the movements and interactions of different tectonic plates and microplates in the region.

Figure 12.2.2 Cross section through the southern Sacramento Valley

This image is a geological cross-section depicting the stratigraphy and fault structures of the Great Valley Sequence in California in the Sacramento Valley. The cross-section runs from west (W) to east (E) and includes detailed labels of various geological formations and features.

The left side of the cross-section shows undifferentiated nonmarine strata and volcanics, with specific layers labeled as Markley and Nortonville. Below these layers are undifferentiated marine strata, depicted in gray to indicate shale dominance, and a section labeled Martinez. The Kirby Hills Fault, marked by a red dashed line, separates these layers from the main Great Valley Sequence.

The Great Valley Sequence, predominantly sandstone-dominant and shown in light yellow, is divided into several formations including Mokelumne River, Starkey, Winters, Sacramento Shale, and Forbes. The Midland Fault, another significant fault, is also marked and separates different sections within the Great Valley Sequence.

Towards the right side of the cross-section, undifferentiated nonmarine strata are depicted again, along with the Basement Complex shown in pink, indicating older, pre-Upper Cretaceous rocks.

The top of the cross-section features labels indicating various geographic locations such as Suisun Bay, Kirkly Hill, Denverton Creek, Lindsey Slough, River Island, Walnut Grove, Thornton, Highway 99, Galt, and Lodi. The lower right corner includes an inset map of California, highlighting the area covered by the Great Valley Sequence with a shaded region.

Overall, this geological cross-section illustrates the complex stratigraphy and fault structures within the Great Valley Sequence, showing the relationships between different geological layers and the significant fault lines that affect them.

Figure 12.2.3: Astronaut photograph of Sutter Buttes

This image is an aerial view of a landscape, showing a central mountainous area surrounded by agricultural land and urban development. The central feature is labeled as the "central core," which appears as a rugged, elevated area with radial patterns of erosion. Surrounding the central core is a region labeled "moat," which appears to be a lower-lying area encircling the central core.

Further out from the central core and moat is a larger area labeled "debris apron," which consists of material that has spread out from the central core, forming a fan-like pattern. This debris apron is a mix of rough terrain and flatter areas used for agriculture.

To the right of the central core and debris apron, the landscape transitions into a grid of fields and agricultural plots. The fields are green and brown, indicating different stages of crop growth or types of land use. On the far-right side of the image is Yuba City, an urban area with a denser network of streets and buildings.

The overall image captures the geological and human-modified features of the landscape, highlighting the relationship between the natural mountainous region and the surrounding agricultural and urban areas.

Figure 12.2.4: Cross section through the southern San Joaquin Valley

This image is a geological cross-section depicting the stratigraphy and fault structures of the Great Valley Sequence in California, in the San Joaquin Valley, specifically focusing on the area from west (W) to northeast (NE). The cross-section includes detailed labels of various geological formations and fault lines, illustrating the complex subsurface geology of the region.

On the left side of the cross-section, labeled as "B," the stratigraphy includes formations such as Paso Robles, Simmler, and Kreyenhagen. These layers are separated by the prominent San Andreas Fault, marked by a red line with arrows indicating relative motion. To the right of the San Andreas Fault is the Granitic Basement, indicating older, more stable rock formations.

Moving eastward, the Great Valley Sequence is depicted as a series of alternating shale-dominant (gray) and sandstone-dominant (light yellow) layers. Key formations within this sequence include the San Joaquin, Reef Ridge, Etchegoin, Antelope, Stevens, and Fruitvale. Several fault lines, marked with red and black dashed lines, cut through these layers, indicating significant geological activity.

Further to the northeast, the Kern River and the Kern River Fault are prominent features. The Kern River Fault is marked by a red line and indicates a significant geological boundary. The formations in this area include Santa Margarita, Vedder, and the Basement Complex, consisting of Jurassic granitic and pre-Cretaceous meta-sediments, shown in pink.

The top of the cross-section features labels indicating various geographic locations such as Elk Hills, North Cross Levee, CA Canal, Strand, McClung, Bellevue, Frendale, and Round Mountain. The lower right corner includes an inset map of California, highlighting the area covered by the Great Valley Sequence with a shaded region.

Overall, this geological cross-section illustrates the complex stratigraphy and fault structures within the Great Valley Sequence, showing the relationships between different geological layers and the significant fault lines that affect them. The cross-section provides a detailed view of the subsurface geology, highlighting the interaction between different formations and fault systems in this region.

Figure 12.2.5: Diorama of deposition from the moving Salinian Granitic Block

This image is a 3D geological cross-section diagram depicting the complex fault structures and stratigraphy of a region in California. The diagram is oriented with north (N) at the top and includes a map inset of California in the lower left corner, showing the location of the cross-section. The cross-section illustrates a series of faulted and folded geological layers, with labels indicating various formations and geographic locations.

Key features include the San Andreas Fault, which runs diagonally from the lower left to the upper right, marked prominently as a major fault line. The Buena Vista Hills are located centrally, with various geological layers shown folded and faulted around this area. To the left side of the diagram are the Elk Hills and Buena Vista Hills, with the Elk Hills showing a complex structure of faulted layers. Towards the upper right, the areas of Fruitvale and Rosedale are indicated, showing regions affected by the geological structures. Various geological layers are labeled with names such as Stevens, Vedder, Paloma, Chanac, and others, shown in different colors and patterns to indicate their composition and geological age.

The diagram also includes features like the CAL Canal, Bakersfield area, Edison High, and the Sierra Nevada to provide geographic context. The vertical scale on the lower left shows measurements in meters and feet, while the horizontal scale indicates distances in miles and kilometers. Overall, this 3D cross-section provides a detailed view of the geological structures in the region, highlighting the interaction between different formations and the impact of major fault lines like the San Andreas Fault. The diagram effectively conveys the complexity of the subsurface geology, showing how various layers have been deformed and displaced over time.

Figure 12.2.6: From the bottom of the image to the top: Rhythmic layering of shale and sandstone

This image shows a close-up view of a rock outcrop with distinct stratification, featuring layers of different rock types. A pen is placed horizontally across the outcrop, providing a sense of scale and highlighting a specific layer. The rock layers exhibit variations in color and texture, with darker and lighter bands alternating. The darker layers appear to be shale or mudstone, characterized by fine-grained material and a more weathered surface. The lighter layers are likely composed of more resistant materials such as sandstone.

The pen, positioned near the center of the image, serves as a reference point for the thickness and orientation of the layers. The presence of the pen also emphasizes a particular feature within the rock, possibly a vein of quartz or calcite, which stands out due to its lighter color and crystalline appearance. This vein runs parallel to the stratification of the rock, indicating a secondary geological process that occurred after the initial deposition of the sedimentary layers.

Overall, the image provides a detailed view of the rock's stratigraphy and highlights the different compositions and textures present in the outcrop. The inclusion of the pen for scale helps to contextualize the size and features of the rock layers, offering insights into the geological history and processes that formed them.

Figure 12.2.7: Scanning electron microscope image of diatomite

This image is a scanning electron microscope (SEM) photograph showing a highly magnified view of microstructures. The main part of the image reveals a complex arrangement of tiny, intricate structures with various textures and patterns. The magnification scale indicates that the image includes features at a microscopic level, with a scale bar showing 100 microns for reference.

In the lower right corner of the main image, there is a broken, circular structure with a pattern of holes, resembling a diatom, which is a type of microscopic algae. This circular structure is labeled with a scale bar indicating 100 microns, helping to provide a sense of scale for the other features in the image.

In the upper right corner, there is a zoomed-in inset showing a close-up of a specific area from the main image. This inset focuses on a detailed section with a perforated, lattice-like pattern, similar to the structure of diatom frustules. The scale bar in this inset shows 10 microns, illustrating the fine details of the microstructure.

A label at the bottom of the image states, "A human hair is approximately 70 microns, give or take 20 microns." This provides a point of reference for understanding the size of the structures in the image, emphasizing how small these microscopic features are in comparison to something familiar like the diameter of a human hair.

Overall, this SEM image provides a detailed view of microscopic structures, showcasing the intricate and delicate patterns that are not visible to the naked eye. The included scale bars and comparison to the size of a human hair help contextualize the extreme magnification and the tiny scale of the observed features.

Figure 12.2.8: Oyster beds in the Santa Margarita Formation

This image shows an exposed geological outcrop in a semi-arid landscape. The outcrop consists of several distinct layers of rock and sediment, visible as horizontal bands of varying color and texture. The upper part of the outcrop is capped with a dark, coarse-grained layer, likely composed of basalt or another volcanic rock, which is more resistant to erosion compared to the layers below it.

Below this dark cap, there are several lighter-colored layers of sedimentary rock, which may include sandstone, siltstone, or mudstone. These layers appear to be more easily eroded, as evidenced by the more rounded and weathered appearance of the slope. The outcrop is situated on a hillside covered with sparse vegetation, including dry grasses and small shrubs, typical of a semi-arid environment.

In the foreground, there are more dense bushes and grasses growing along the base of the outcrop. The presence of these plants suggests some accumulation of moisture and soil at the lower levels of the slope. The overall scene depicts a clear example of sedimentary layering, weathering processes, and the impact of vegetation on the landscape in a dry environment.

Figure 12.2.9: Arcida (oyster) from the Santa Margarita Formation

This image shows a close-up view of a fossil specimen, specifically a fossilized oyster, placed on a dark background. The fossil has a rough, irregular surface with a light beige to tan coloration and appears to have a weathered, cracked texture. Next to the fossil is a white measuring card with metric and imperial units, providing a scale for the specimen. The measuring card has a large black arrow pointing to the right, marked with "Z" at the arrowhead and labeled with increments in centimeters along the top and left edges, and inches along the right edge.

The fossil is roughly oval in shape and measures approximately 10 centimeters in length, as indicated by the measuring card. The surface of the fossil shows various cracks and fractures, suggesting that it may have been subjected to weathering or pressure over time. The fossil's texture and appearance indicate it is a fossilized oyster, showcasing the preserved details of its ancient shell.

The overall image provides a clear view of the fossil's size, shape, and texture, with the measuring card serving as a useful reference for scale and orientation. The close-up nature of the photograph allows for detailed examination of the fossil's surface features and composition.

Figure 12.2.10: Carcharodon hastalis (shark) tooth

This image shows two fossilized shark teeth from the extinct white shark species *Carcharodon hastalis*. The teeth are displayed against a dark background, highlighting their distinct features. Both teeth have a triangular shape with sharp, smooth edges and a broad, robust base.

The teeth are labeled with their origin: "Temblor Fm. (Round Mountain Silt), Kern Co. (Sharktooth Hill), CA, USA," indicating that they were found in the Temblor Formation in Kern County, California, specifically at Sharktooth Hill, a well-known fossil site. The slant height of the teeth is noted as "1 9/16” (40 mm)," providing a measurement for the size of the fossils.

Below the image, the scientific name *Carcharodon hastalis* is prominently displayed, along with the common name "Extinct White Shark." The detailed labels and clear presentation emphasize the significance of these fossils as valuable specimens from an extinct species of shark.

Overall, the image provides a detailed and informative view of the fossilized teeth, showcasing their size, shape, and origin, and offering insights into the paleontological significance of these remains.

Figure 12.3.1: Based on the dominant processes operating within a river system

This image is an illustration showing the process of sediment transport in a river system, from its source to its deposition in a sink. The diagram is divided into three main sections: source, transport, and sink, each depicted with corresponding landscapes and processes.

On the right side, labeled "SOURCE," the illustration shows mountains with streams and rivers originating from slopes and migrating river channels. This section highlights that erosion from slopes and river channels generates a lot of sediment. The rivers are shown as blue lines running down the mountains, carrying sediment with them.

In the middle section, labeled "TRANSPORT," the diagram illustrates how rivers move sediment downstream. The rivers are depicted flowing through a more leveled landscape, continuing to carry sediment towards lower elevations.

On the left side, labeled "SINK," the illustration shows the sediment being deposited across natural river deltas and floodplains as the rivers reach their mouths. The rivers are shown spreading out into multiple channels, depositing sediment into a body of water, likely a bay or sound.

To the right of the diagram, there is an explanatory text that reads: "Sediment is the sand, mud, and pebbles that were once solid rock. Sediment flows in tributary streams and river channels of the Skagit, from the Cascade Mountains to Skagit Bay and Puget Sound."

Overall, the illustration provides a clear and simplified view of the sediment transport process in a river system, from its initial erosion in the mountains, through transport by rivers, to its final deposition in deltas and floodplains. The accompanying text helps contextualize the illustration by explaining what sediment is and describing the specific example of the Skagit River system.

Figure 12.3.2: Major rivers of the Great Valley Province

This image is a detailed map of California, focusing on the Great Valley Province and its major rivers. The map shows a shaded area in light blue, representing the Great Valley Province, which stretches from the northern to the southern parts of the state. The Great Valley Province is bordered by various national forests and parks, including Trinity National Forest, Lassen National Forest, Mendocino National Forest, Tahoe National Forest, Eldorado National Forest, Stanislaus National Forest, Inyo National Forest, and Sequoia National Forest.

The map highlights major rivers within the Great Valley Province in blue. Some of these rivers include the Sacramento River, Feather River, American River, Cosumnes River, Mokelumne River, Calaveras River, Stanislaus River, Tuolumne River, Merced River, Chowchilla River, Fresno River, San Joaquin River, Kings River, Tule River, Kaweah River, White River, and Kern River. These rivers are shown flowing through the valley and contributing to the region's hydrology.

The San Andreas Fault is marked with a red line, running parallel to the California coast from the northern part of the state down through the central region, highlighting a significant geological feature.

Several cities and towns are labeled, including Redding, Chico, Sacramento, Fairfield, Santa Rosa, Napa, Concord, San Francisco, Livermore, Fremont, San Jose, Salinas, Modesto, Stockton, Fresno, Bakersfield, and San Luis Obispo. Additionally, nearby states and regions are indicated, with Reno and Carson City in Nevada marked to the east of California.

The map includes a compass rose in the upper right corner for orientation, showing directions (N, S, E, W) and a scale bar at the bottom indicating distances in miles.

Overall, this map provides a comprehensive view of the Great Valley Province in California, emphasizing its major rivers, the San Andreas Fault, and the surrounding geographic and political features.

Figure 12.3.3: A series of terraces along a river

This image is a diagram illustrating the formation and structure of river terraces in a valley. The diagram shows a cross-sectional view of a valley with multiple river terraces, labeled as T1, T2, T3, and T4, each representing different stages of terrace formation. The terraces are colored green and are located at different elevations above the modern floodplain, which is colored yellow. The river itself is depicted in blue, meandering through the modern floodplain.

The key elements of the diagram include the modern floodplain, shown in yellow, representing the youngest and most recent sediment deposition area. River deposits are represented by dotted areas within the floodplain, indicating zones of active sediment deposition by the river. Terrace surfaces are labeled T1, T2, T3, and T4, with T1 being the oldest terrace surface and T4 being the youngest or future terrace. These terraces are depicted in green. Beneath the terraces and floodplain is bedrock, shown in a striped pattern, indicating the solid rock foundation of the valley.

The diagram includes additional annotations and a formula: r1 = h1 / h2, indicating the average rate of incision, where h1 is the height of the T1 terrace, and h2 is another height measurement related to the terrace surfaces. The term t1 represents the age of the T1 terrace surface, while h1 denotes the height of the T1 terrace.

Overall, the diagram provides a visual explanation of how river terraces are formed over time through processes of erosion and deposition. The terraces represent different periods of river activity, where the river has cut down into its bed, leaving behind elevated surfaces that mark previous levels of the floodplain. The inclusion of labels and the formula helps to contextualize the diagram, offering insights into the geological processes that shape river valleys and their terraces.

Figure 12.3.4: Ione formation river terrace near Merced Falls

This image is a black-and-white photograph depicting a pastoral scene with a grassy field in the foreground and a hill in the background. The field is dotted with a few scattered trees, one of which stands prominently in the center of the image. The trees appear to be deciduous, as they are without leaves, suggesting the photo might have been taken in the late fall or winter.

In the background, atop the hill, there is a structure or collection of structures, partially obscured by trees and the hill's slope. These structures appear to be ruins or possibly an old fortification, as indicated by their rough, stone-like appearance and irregular outlines. The hill itself is sparsely vegetated, with patches of grass and some small shrubs.

The overall scene is tranquil and seems to be set in a rural or semi-rural area, characterized by open spaces and natural elements. The photograph captures a moment of stillness, highlighting the contrast between the open, grassy field and the more rugged, structured hill in the background. The lack of leaves on the trees and the presence of the ruins give the image a somewhat desolate yet serene atmosphere.

Figure 12.4.1: Land subsidence near Hanford, CA

This image is a comparative photograph showing land subsidence in the San Joaquin Valley, California, over several decades. The image is divided into two parts, each highlighting a specific time period and amount of subsidence.

The left part of the image, taken in 1977, shows a man standing next to a utility pole with a sign reading "San Joaquin Valley, California, BM 5861, Subsidence 9M, 1925-1977." The sign indicates the amount of land subsidence that has occurred between 1925 and 1977. The pole is marked with the year 1955 near the top, showing the level of the ground in 1955, and the man stands next to a marker indicating the ground level in 1977. The background features a field of crops, illustrating the agricultural setting of the area.

The right part of the image, taken in 2016, shows a woman standing next to a measuring rod with signs indicating subsidence levels for the years 1988, 2004-2008, and 2016. The woman holds a sign reading "San Joaquin Valley, California, Subsidence 6.2 ft, 1988-2016, USGS 2016." This part of the image also highlights the amount of land subsidence that has occurred over the specified period. The background shows a concrete barrier and an open field, emphasizing the ongoing nature of the subsidence issue.

Together, these photographs provide a visual representation of the significant land subsidence in the San Joaquin Valley over multiple decades. The images effectively illustrate the dramatic changes in ground level and highlight the impact of subsidence on the region. The presence of the individuals and markers for different years offers a clear and tangible sense of the extent of subsidence over time.

Figure 12.4.2: 2017 map of the San Joaquin Valley showing the measured subsidence from synthetic aperture radar (SAR)

This image is a map depicting the measurements of land subsidence in the San Joaquin Valley, California, for the year 2017. The map uses a color gradient to illustrate varying levels of subsidence, with dark purple representing less subsidence and bright yellow to orange indicating greater subsidence. The color scale on the map ranges from -0.5 feet to 1.5 feet, showing the depth of subsidence across the region.

The San Joaquin Valley is outlined in black, encompassing a large central portion of California. Major cities and towns within and around the valley are marked, including Stockton, Modesto, Turlock, Merced, Atwater, Los Banos, Fresno, Hanford, Tulare, Visalia, Delano, Porterville, Bakersfield, and more.

The map shows significant subsidence areas particularly in the central and southern parts of the valley, with noticeable concentrations around Merced, Atwater, Los Banos, and Fresno, where the colors shift towards bright yellow and orange, indicating higher subsidence levels. Northern and peripheral areas of the valley show less subsidence, represented by darker purple shades.

Surrounding geographical features and landmarks such as the Sierra National Forest, Yosemite National Park, Kings Canyon National Park, and Los Padres National Forest are also labeled, providing context for the valley's location within the broader landscape of California.

The map includes a compass rose in the upper right corner for orientation and a scale bar at the bottom indicating distances in miles, helping to understand the spatial extent of the subsidence. The title "2017 Subsidence Measurements" along with "SAR 2017" indicates that the data was collected using Synthetic Aperture Radar (SAR) technology.

Overall, this map provides a clear visualization of the areas within the San Joaquin Valley that experienced varying degrees of land subsidence in 2017, highlighting the regions most affected by this geological process.

Figure 12.4.3: Approximate extent of Tulare Lake

This image is a map illustrating the approximate historical extent of Tulare Lake in California. The main map shows a detailed satellite view of the region with Tulare Lake marked in light blue, indicating its former size and location.

Major rivers that feed into the lake, such as the San Joaquin River, Kings River, Tule River, and Kaweah River, are highlighted in blue. These rivers are significant in the region's hydrology and their connections to the lake are clearly depicted. The San Andreas Fault is marked with a red line, running through the southwestern part of the map, indicating its geological significance in the area.

The map labels various towns and cities within and around the former lakebed, including Fresno, Clovis, Hanford, Lemoore, Visalia, Tulare, Delano, Wasco, Shafter, and Bakersfield. The agricultural and urban landscape surrounding the former lake is visible, with numerous fields and grid-like patterns indicating extensive farming activities.

In the top left corner, there is an inset map providing a broader view of California, showing the location of the main map area in relation to the entire state. The inset map includes major cities such as San Francisco, Los Angeles, and other landmarks to provide geographic context.

The map includes a compass rose in the upper right corner for orientation and a scale bar at the bottom indicating distances in miles, which helps in understanding the spatial extent of the historical lake.

Overall, this map effectively visualizes the historical extent of Tulare Lake, highlighting its size and the major rivers that contributed to it, along with the current geographic and urban features of the region.

Figure 12.4.4: A March 2023 pineapple express storm brought the resurgence of Tulare Lake

This image shows a road that is partially submerged in water, with a clear "ROAD CLOSED" sign prominently displayed in the foreground. The road extends straight ahead into the distance, bordered by water on both sides, suggesting that it is either a causeway or a road through a flood-prone area.

In the foreground, the "ROAD CLOSED" sign is accompanied by orange traffic cones, sandbags, and barriers to prevent vehicles from proceeding further. The sign is mounted on a barricade with two orange warning lights on top, which are likely to be flashing to alert drivers of the hazard. Additionally, there is another smaller sign behind the main barricade that reads "WATER OVER ROAD."

The scene is set under a blue sky with scattered clouds, and the water level appears calm but high enough to have submerged part of the road. Power lines run parallel to the road, stretching into the distance, and the surrounding landscape appears flat and expansive.

The image effectively captures a moment of road closure due to flooding, illustrating the impact of high water levels on infrastructure and the measures taken to ensure safety by closing the road and warning drivers of the hazard. The peacefulness of the scene contrasts with the underlying issue of flooding and the potential disruption it causes.

Figure 12.4.5: Dry Tulare Lake south of Lemoore, CA

This image is a map showing the approximate extent of the historical Tulare Lake, which is now dry. The main map features a detailed satellite view of the region with the outline of Tulare Lake marked in light blue, indicating where the lake once existed. Major rivers, including the San Joaquin River, Kings River, Tule River, Kaweah River, and White River, are highlighted in blue, showing their pathways and connections to the lake area.

The San Andreas Fault is indicated with a red line running through the southwestern part of the map, marking its significant geological feature. The map includes several towns and cities, such as Fresno, Clovis, Visalia, Tulare, Hanford, Lemoore, Delano, Wasco, Shafter, Bakersfield, Huron, Avenal, and Coalinga, providing context for the surrounding human geography.

In the top left corner, an inset map shows the broader geographical context of California, highlighting the location of the main map area within the state. This inset includes major cities such as San Francisco and Los Angeles for reference.

The map features a compass rose in the upper right corner for orientation and a scale bar at the bottom, indicating distances in miles. The title "Approximate Extent of Tulare Lake" along with the legend differentiates between major rivers, the San Andreas Fault, and the historical extent of Tulare Lake.

Overall, this map provides a visual representation of the historical extent of Tulare Lake, emphasizing the major rivers that contributed to it and the current geographical and urban features in the region.

Figure 12.4.6: “Shaking Hazard Potential”

This image is a map depicting the shaking hazard potential in California and parts of neighboring states. The map uses a color gradient to represent different levels of seismic hazard, ranging from blue for the lowest hazard to red for the highest hazard. This gradient shows areas at risk for seismic activity and potential ground shaking.

The San Andreas Fault, a major geological feature known for its seismic activity, is prominently marked on the map. Other faults are also indicated, contributing to the overall understanding of seismic risk in the region. The map highlights the Great Valley Province with a blue outline, encompassing the central valley of California.

Major cities and towns are labeled, including Sacramento, San Francisco, San Jose, Fresno, Los Angeles, San Diego, and more. The map also extends to neighboring regions, showing parts of Nevada, with cities like Carson City and Las Vegas marked. Medford in Oregon and Boise in Idaho are also labeled, providing a broader geographic context.

The highest hazard areas are concentrated along the San Andreas Fault, particularly around the Los Angeles and San Francisco regions, where the color shifts to red. Lower hazard areas are indicated by blue and purple shades, found in the central and eastern parts of California and extending into Nevada.

The map includes a compass rose in the upper right corner for orientation and a scale bar at the bottom, indicating distances in miles. The legend titled "Shaking Hazard Potential" explains the color gradient used to represent different levels of seismic risk, along with markings for faults and the Great Valley Province.

Overall, this map provides a comprehensive visualization of seismic hazard potential in California, highlighting areas most at risk for significant ground shaking due to earthquakes. It emphasizes the importance of understanding seismic risks for urban planning and safety in these regions.

Figure 12.4.7: “Nunez Fault: 1983 Coalinga-Naschmarkt Earthquake Location”

This image is a detailed map illustrating the location of the 1983 Coalinga-Naschkmarkt Earthquake along the Nunez Fault. The map covers a region in California near the city of Coalinga and highlights various fault lines and geological features.

The Nunez Fault, where the earthquake occurred, is prominently marked in red. The map shows other faults in the region, including the San Andreas Fault, which is highlighted in red with a thick line and significant historical rupture points marked with dates such as "1857" and "1901." The San Andreas Fault runs along the western side of the map, illustrating its major impact on the region's geology.

The map includes several labels for geographic locations and features, such as the Diablo Range, Alcalde Hills, and Pleasant Valley. The town of Coalinga is marked with a magenta outline, showing its proximity to the Nunez Fault. Other notable locations include the Lemoore Naval Air Station and various hills and valleys in the area.

Various fault types are indicated with different line styles, explained in the legend at the bottom of the map. The legend details the symbols used for surface rupture points, fault certainty, structural discontinuities, pre-Quaternary faults, and Quaternary faults. This comprehensive legend helps interpret the geological features and fault lines displayed on the map.

In the top right corner, an inset map provides a broader geographic context, showing the location of the main map area within California. Major cities such as San Francisco, Los Angeles, and San Diego are marked, helping to situate the earthquake location within the state.

The map includes a compass rose for orientation and a scale bar indicating distances in miles and kilometers. The title "Nunez Fault: 1983 Coalinga-Naschkmarkt Earthquake Location" clearly defines the map's focus, and the date "7/19/2023" indicates the publication or update date of the map.

Overall, this map provides a detailed and informative view of the geological features and fault lines in the Coalinga region, emphasizing the location and context of the 1983 earthquake along the Nunez Fault.

Figure 12.4.8: Building at 187 South 6th Street, Coalinga, CA

This image is a black-and-white photograph showing the aftermath of an earthquake, likely from the 1983 Coalinga earthquake, given the previous context. The scene depicts significant structural damage to buildings and scattered debris.

In the foreground, there is a car covered in debris, suggesting that parts of the nearby structures collapsed onto it. Behind the car, a person is walking through the rubble, which covers the ground extensively, indicating a considerable amount of destruction. The person appears to be either a rescue worker or a bystander assessing the damage.

The background shows a building that has partially collapsed. The structure's upper floor has fallen, causing the lower part of the building to crumble and disintegrate. Walls and ceilings are visibly damaged, with interiors of rooms exposed due to the collapse. The remains of the building are surrounded by a large amount of debris, including bricks, concrete, and other construction materials.

Overall, the photograph captures the severe impact of the earthquake, highlighting the destruction of infrastructure and the chaotic scene in the aftermath. The presence of the person in the image adds a human element, emphasizing the scale of the disaster and the immediate response to assess and address the damage.

Figure 12.5.1: Map of the San Joaquin basin during the late Miocene

This image is a geological map illustrating the distribution of various geological formations and features in the San Joaquin Valley, California during the late Miocene. The map highlights both marine and non-marine environments, with a focus on volcanic formations and major fault lines.

The San Andreas Fault is prominently marked in red, running diagonally from the bottom center of the map near Santa Cruz, continuing up past Coalinga, and into the region near San Francisco. This fault line is a major geological feature in California known for its seismic activity.

Marine environments are indicated with blue shades. Basins, where deeper marine sediments are found, are colored dark blue, while shelves, representing shallower marine areas, are colored light blue. These areas are primarily located along the western edge of the map, adjacent to the Pacific Ocean.

Non-marine environments are depicted in different colors. Volcanic areas are shown in pink, with labels such as "Quien Sabe Volcanics," "Stanislaus Volcanics," and "San Joaquin Volcanics" indicating the locations of these formations. Lowlands, which are areas of lower elevation, are colored beige, and highlands, which are higher elevation areas, are colored yellow.

Several cities and geographical features are labeled on the map. These include San Francisco, Santa Cruz, Coalinga, Stockton, Fresno, Bakersfield, and Mount Diablo. Rivers and water bodies are depicted in blue lines, showing the drainage patterns and hydrology of the region.

The map also includes a compass rose for orientation, pointing north, and a scale bar indicating distances in kilometers. The legend in the lower right corner explains the color coding and symbols used on the map to represent different geological and geographical features.

Overall, this geological map provides a comprehensive overview of the diverse geological formations and environments in the region, highlighting key features such as volcanic areas, marine basins, and the San Andreas Fault.

Video 12.5.1: Oil and Gas Formation

What drives our cars, buses and planes, powers our electricity and allows us to cook our food and heat our water? Most of today's energy needs are met by fossil fuels like coal, oil and gas. These unique high energy fuels are non-renewable resources that took millions of years to form. About two billion years ago, marine organisms like algae and microscopic animals and plants died and settled on the ocean floor.

Beneath other sediments in the ocean and in the absence of oxygen, these fossils changed into a substance called kerogen. Under heat and pressure, kerogen gradually changes into oil or gas. The whole process usually takes at least a million years.

At the molecular level, oil and gas are hydrocarbons made up of hydrogen and carbon atoms. The constant pressure and movement of the Earth's crust squeezes oil and gas through the pores or spaces within rocks. Some oil and gas reaches the Earth's surface and seeps out naturally into land or water.

Often it is trapped beneath the surface by impermeable layers or rock structures like faults and folds. Within the crust, oil or gas deposits build up and form reservoirs. Reservoirs are like vast sponges filled with oil and gas.

They can be as large as a city. To find oil and gas deposits, geologists use a number of different survey techniques, including seismic surveys, gravitational surveys and geological mapping. Seismic surveys use reflected sound waves to produce a 3D view of the Earth's interior.

New technologies, such as four dimensional projections and sophisticated graphic renderings of rock structures, are improving the way we find conventional oil and gas deposits. Energy resources that are currently difficult or expensive to extract are called unconventional oil and gas. In a world with limited energy resources, people are looking at more efficient ways of tapping into unconventional oil and gas or at alternative and renewable sources of energy from biofuels or the sun.

What do you think will be the energy sources of the future?

Figure 12.5.2: "Migration of oil and gas”

This image is a cross-sectional diagram illustrating the geological processes involved in the formation and migration of oil and gas. The diagram shows different layers of rock and the conditions under which oil and gas are trapped and stored.

The top layer of the diagram is labeled "Impermeable cap rocks," shown in brown. These rocks act as a seal, preventing the upward movement of oil and gas. Below this layer are "Reservoir rocks," depicted in a lighter color, which are porous and capable of storing hydrocarbons.

Beneath the reservoir rocks are the "Source rocks," highlighted in shades of green and red. These rocks contain organic material that, under heat and pressure, transforms into oil and gas. The depth of these layers is marked on the left side of the diagram, ranging from 0 to 5 kilometers.

The diagram also shows different types of traps where oil and gas can accumulate. An "Anticline trap" is formed by the upward arching of rock layers, creating a pocket where oil and gas can collect. A "Fault trap" is created by the movement of rock along a fault line, which can trap hydrocarbons in the displaced rocks. A "Stratigraphic trap" is formed by variations in rock layers, such as changes in rock type or thickness, which can trap hydrocarbons. A "Reef or salt trap" is formed by the presence of a reef or salt dome, creating a barrier that traps oil and gas.

The diagram highlights the migration of oil and gas with red dashed arrows, showing the movement from the source rocks to the reservoir rocks. The "Oil window" and "Gas window" are also indicated, representing the depth ranges where temperatures and pressures are sufficient to convert organic material into oil and gas, respectively.

Overall, this diagram provides a detailed overview of the geological conditions and processes involved in the formation, migration, and trapping of oil and gas, illustrating the complexities of hydrocarbon accumulation in the Earth's subsurface.

Figure 12.5.3: Diagram showing the structure of several different types of oil and gas traps

This image is a series of four cross-sectional diagrams illustrating different types of geological traps for oil and natural gas. Each diagram shows how hydrocarbons are trapped in the Earth's subsurface and how they are accessed by drilling.

The first diagram, labeled "Anticline Trap," shows a fold in rock layers forming an arch, with oil and natural gas accumulating at the crest of the fold. The layers include impermeable shale clay (A), porous reservoir rock (B), and source rock (C). An oil well (D) is depicted drilling into the reservoir rock, extracting the trapped hydrocarbons.

The second diagram, labeled "Fault Trap," depicts a geological fault where rock layers are displaced. The fault creates a barrier, trapping oil and natural gas in the reservoir rock against the impermeable shale clay. The oil well (D) drills into the reservoir rock to access the hydrocarbons.

The third diagram, labeled "Oil Traps on Salt Dome Flanks," illustrates how a salt dome can create traps for hydrocarbons. The salt dome pushes upward, deforming the surrounding rock layers. Oil and natural gas accumulate on the flanks of the dome, trapped by the impermeable shale clay and fault structures. An oil well (D) is shown drilling into the reservoir rock on the flank of the salt dome.

The fourth diagram, labeled "Stratigraphic Trap," shows how variations in rock layers can create traps for hydrocarbons. Changes in rock type or thickness can isolate pockets of oil and natural gas in the reservoir rock, with impermeable shale clay forming a seal. The oil well (D) drills into the reservoir rock to extract the trapped hydrocarbons.

In all diagrams, the key elements are labeled: A represents impermeable shale clay, B represents porous reservoir rock, C represents source rock, and D represents the oil well. These diagrams provide a clear visual explanation of the different mechanisms by which oil and natural gas can be trapped and accessed in the Earth's subsurface.

Figure 12.5.4: Wildcatters pushing their luck at drilling oil wells

This image is a black-and-white photograph depicting a group of oil workers posing in front of an oil drilling rig. The scene appears to be from an earlier era of oil exploration, likely in the early to mid-20th century, judging by the attire and equipment.

The workers, about twenty in number, are dressed in work overalls and hats, many of them covered in oil and grime, indicating they have been working hard in the field. They are standing and crouching in rows, looking directly at the camera with expressions ranging from serious to slightly smiling. The group is positioned in front of the oil rig, which towers above them and dominates the background.

The drilling rig itself is a tall, lattice-like structure made of metal, typical of the oil rigs used during that period. There is a significant amount of equipment and machinery at the base of the rig, with piles of earth and materials scattered around. In the background, there are some industrial buildings and storage tanks, likely used for processing and storing the oil extracted from the well.

The landscape around the rig is barren, with sparse vegetation and signs of heavy industrial activity. Utility poles with wires stretch across the scene, suggesting the presence of necessary infrastructure to support the drilling operations.

Overall, this photograph captures a moment in the daily life of oil workers during the early days of oil exploration and drilling, highlighting the physical demands of the job and the industrial nature of the work environment. The image serves as a historical snapshot of the oil industry's development and the people who worked in it.

Figure 12.5.5: Sediment core

This image shows a collection of sediment cores taken from the ocean, displayed in vertical sections. Each core is housed in a long, narrow box, allowing for a clear view of the different layers of sediment that have accumulated over time. The cores are aligned side by side, with labels at the top indicating specific depths or sections.

The sediment cores display a variety of colors and textures, ranging from lighter shades of beige and brown to darker tones of gray and black. These variations represent different types of sediment and geological periods, providing valuable information about the ocean's history and environmental changes.

The layers within each core are distinct, showing horizontal stratification that indicates different depositional events. Some layers appear more homogeneous, while others show more variation and complexity, such as changes in grain size or the presence of distinct sedimentary structures.

The cores are meticulously labeled, with small tags at the top of each section to ensure accurate identification and reference. At the bottom right corner of the image, a notation "14 PS1920–" is visible, likely serving as an identifier for the specific core or collection of cores.

Overall, this image captures the detailed and informative nature of ocean sediment cores, showcasing their importance in understanding the geological and environmental history of the Earth's oceans.

Figure 12.5.6: “Corcoran Clay Thickness”

This image is a map depicting the thickness of the Corcoran Clay layer in California's Central Valley. The map shows variations in the thickness of the clay layer using a color gradient, with darker colors representing greater thickness and lighter colors indicating thinner layers. The gradient ranges from light yellow to dark brown, and the legend at the bottom left indicates that the thickness varies from 6.88 feet to 198.24 feet.

Contour lines are overlaid on the color gradient to provide precise measurements of the clay thickness. These lines are labeled with numerical values indicating the thickness in feet, offering detailed information about the distribution of the clay layer. The study area is outlined in black, encompassing a significant portion of the Central Valley, providing a clear boundary for the analyzed region.

Major cities within the study area are labeled, including Stockton, Modesto, Merced, Fresno, Tulare, Lemoore, and Bakersfield. These labels help provide geographic context for the clay thickness data, making it easier to understand the implications for different parts of the valley. Additionally, a compass rose is located at the top right corner of the map, indicating north for orientation, and a scale bar at the bottom right corner provides a reference for distance, indicating 0, 12.5, 25, and 50 miles.

The map highlights that the thickest areas of the Corcoran Clay layer are located primarily in the western and central parts of the valley, with thinner layers towards the eastern edges. This distribution is critical for understanding groundwater flow, subsidence, and agricultural practices in the region, as the Corcoran Clay acts as a significant confining layer affecting these factors. Overall, this map provides a detailed and informative visualization of the Corcoran Clay thickness across the Central Valley, helping to understand its geological and hydrological implications.

Figure 12.5.7: “Great Valley Province oil and gas fields”

This image is a detailed map showing the Great Valley Province in California, highlighting oil and gas fields, the San Andreas Fault, and surrounding geographical features. The Great Valley Province is shaded in light blue, encompassing a large portion of central California, known for its significant agricultural and industrial activities.

The map marks oil and gas fields within the Great Valley Province in green. These fields are distributed throughout the region, with notable concentrations near Bakersfield, Fresno, and Stockton. The presence of these fields indicates areas of active or potential hydrocarbon extraction, which is crucial for understanding the region's economic and industrial landscape.

The San Andreas Fault, a major geological feature known for its seismic activity, is prominently marked with a red line running diagonally from the northwest to the southeast, passing near cities such as San Francisco, San Jose, and Bakersfield. This fault line is a key factor in the geological stability and earthquake risk of the area.

The map also labels major cities and towns, including Redding, Chico, Sacramento, Stockton, Modesto, Fresno, Visalia, Bakersfield, Santa Rosa, Napa, Fairfield, Concord, Livermore, Fremont, San Jose, Salinas, San Luis Obispo, and Santa Maria. These labels provide context for the human geography of the region, showing the proximity of urban centers to the oil and gas fields.

Surrounding natural features and national forests, such as the Trinity National Forest, Mendocino National Forest, Lassen National Forest, Tahoe National Forest, Eldorado National Forest, Stanislaus National Forest, Sierra National Forest, Sequoia National Park, and Sequoia National Forest, are also marked, highlighting the diverse landscapes that make up California.

The map includes a compass rose in the upper right corner for orientation and a scale bar at the bottom indicating distances in miles, providing a reference for the scale of the area depicted. The title "Great Valley Province Oil & Gas Fields" along with the legend helps to interpret the map's focus on hydrocarbon resources within the broader geographical context of the region.

Overall, this map provides a comprehensive visualization of the Great Valley Province, emphasizing the distribution of oil and gas fields, the significance of the San Andreas Fault, and the region's major urban and natural features.