9.9: Detailed Figure Descriptions

Intro Image

The map titled "Geomorphic Provinces of California" illustrates the diverse geological regions within the state. California is divided into distinct geomorphic provinces, each characterized by unique geological features and landscapes. These provinces include the Klamath Mountains in the northwest, known for their rugged terrain and ancient rocks, and the Modoc Plateau in the northeast, which is a volcanic highland area. The Cascade Range, found to the north of the state, is part of a major volcanic arc in North America.

Moving southward, the Northern and Southern Coastal Ranges run parallel to the Pacific coast, featuring a mix of mountain ranges and valleys. The Great Valley, located in the central part of the state, is a large and fertile agricultural region. The Sierra Nevada, one of the most prominent mountain ranges in California, runs north to south along the eastern edge of the Great Valley and is known for its dramatic peaks and alpine scenery.

To the east of the Sierra Nevada lies the Basin and Range province, characterized by a series of alternating basins and mountain ranges. The Mojave Desert, located in the southeastern part of the state, is a vast arid region with a unique desert landscape. The Transverse Ranges, located in southern California, run east to west, which is unusual compared to the general north-south orientation of most California mountain ranges.

Further south, the Peninsular Ranges extend into Baja California, featuring coastal mountains and valleys. Lastly, the Colorado Desert, situated in the southeastern corner of the state, is part of the larger Sonoran Desert and is known for its extremely arid conditions and distinctive desert features. Each of these geomorphic provinces contributes to the rich geological diversity of California, shaping its natural environment and influencing human activities within the state.

Figure 9.1.1 As Air Rises up the Windward/Western Side of the Sierra Nevada Mountains

The image is a simplified cross-sectional diagram illustrating the process of orographic lift, which affects weather patterns across California's diverse landscapes. Starting from the left, the image depicts the Pacific Ocean with a blue arrow indicating the movement of moist air from the ocean towards the land.

As the air reaches the Coast Range, a small mountain range shown in green, it begins to rise due to the topography. This rising air cools as it ascends, depicted by the blue arrow moving upwards over the range. As the air cools, it can hold less moisture, leading to cloud formation and potential precipitation, represented by a small cloud over the Coast Range.

The air then descends into the Central Valley, depicted as a flat, green area between the Coast Range and the Sierra Nevada mountains. The red arrow shows the air warming up as it descends, reducing the likelihood of precipitation in the valley.

Next, the air encounters the Sierra Nevada mountains, a larger and more prominent mountain range shown in a darker green. As the air is forced to rise sharply over these higher elevations, it cools rapidly, leading to significant cloud formation and precipitation, shown by a larger cloud and vertical blue lines indicating rain or snow on the windward side of the mountains.

Finally, the air descends into the Great Basin, depicted as a brown area on the far right. As the air moves down the leeward side of the Sierra Nevada, it warms up and dries out, represented by the red arrow continuing its descent. This results in a rain shadow effect, where the Great Basin and other areas east of the Sierra Nevada receive much less precipitation, leading to a more arid climate.

Overall, the image visually explains how the topography of California influences weather patterns, particularly the distribution of precipitation, which is critical for understanding the region's climate and ecosystems.

Figure 9.1.2 The Sierra Nevada mountain range is asymmetric with a shallowly sloped western side and a notably steeper eastern side

The image is a three-dimensional block diagram illustrating the geological structure of the Sierra Nevada mountain range in California. The diagram is oriented to show the relationship between the Sierra Nevada, the Central Valley of California, and the Mono Basin.

Starting on the left side, the Central Valley of California is depicted as a flat, tan-colored area representing the large, fertile basin located west of the Sierra Nevada. This valley is known for its extensive agriculture, benefiting from the fertile soils and relatively gentle topography.

Moving to the right, the Sierra Nevada mountains are illustrated in green, highlighting the rugged and elevated terrain that characterizes this mountain range. The diagram shows the complex network of rivers and streams (depicted as black lines) that drain from the higher elevations towards the Central Valley. These waterways originate in the high peaks and carve through the landscape, contributing to the dramatic topography of the region.

On the right side of the diagram, the eastern slope of the Sierra Nevada drops sharply towards the Mono Basin, represented by a grey area with vertical red lines indicating active faults. The Mono Basin lies in a tectonically active region, with faults contributing to the uplift of the Sierra Nevada and the subsidence of the basin. The arrows and red lines emphasize the geological forces at play, particularly the extension (pulling apart) occurring in the region.

The overall image provides a clear visual representation of the topographic and geological relationship between the Central Valley, the Sierra Nevada, and the Mono Basin, illustrating the tectonic processes that have shaped this dynamic landscape.

Figure 9.1.3 Relief and fault map of the Sierra Nevada

The relief map of the Sierra Nevada region illustrates the diverse topography and significant geological features, including various fault lines that shape the landscape. Elevation is color-coded, with green indicating lower elevations and brown to white representing higher elevations. The map highlights several major faults, including the Fort Sage Fault, Kern Front Fault, Hilton Creek Fault, Kern Canyon Fault, Owens Valley Fault, Southern Sierra Nevada Fault, Garlock Fault, White Wolf Fault, and Little Lake Fault. These faults are marked prominently with black lines, indicating their locations and extents.

The map also shows key geographical features and cities such as San Francisco, San Jose, Sacramento, and Fresno, providing a reference for the location of these faults within the broader context of California's geography. Additionally, the elevation scale provided on the map gives a clear understanding of the varying altitudes across the Sierra Nevada region, from the low-lying valleys to the high mountain peaks. This detailed depiction aids in comprehending the complex interplay between tectonic activity and topography in the Sierra Nevada, offering insights into the region's geological history and ongoing processes.

Figure 9.1.4 The major river systems in California

The image is a detailed map showing the major rivers of California. The map is oriented with north at the top and highlights the extensive network of rivers and water bodies across the state.

California's rivers are depicted in blue, with the most prominent ones labeled, including the Sacramento River, San Joaquin River, Kern River, and the Colorado River. The rivers meander across various regions of the state, flowing from the mountainous areas toward lower elevations, eventually draining into the Pacific Ocean or inland basins.

The map also shows major lakes and reservoirs in light blue, such as Lake Tahoe, Clear Lake, and the Salton Sea. Dry lakes, indicated by dashed lines, are visible in areas like the Mojave Desert, highlighting the state's diverse hydrological features.

The terrain's topography is subtly represented, showing the Sierra Nevada mountain range along the state's eastern edge, the Central Valley through which many of the rivers flow, and the coastal ranges to the west. The map provides a comprehensive overview of California's water system, emphasizing the importance of rivers in the state's geography and ecology.

Overall, this map serves as a vital tool for understanding the distribution and flow of water across California, showcasing the intricate connections between its rivers, lakes, and the surrounding landscape.

Figure 9.2.1 An illustration of what western North America may have looked like during the Paleozoic era

The image depicts a cross-sectional diagram illustrating the process of ocean-to-oceanic convergence. The diagram shows two tectonic plates, the oceanic crust, and the continental crust, converging at a subduction zone.

On the left side, the oceanic crust is descending beneath another section of oceanic crust into the Earth's mantle, forming a deep oceanic trench at the boundary. This process is known as subduction. As the oceanic plate descends, it melts due to the high temperatures and pressures within the mantle, leading to the formation of magma.

The magma rises through the overlying plate, eventually reaching the surface, where it forms volcanic islands known as an island arc. These islands are typically located parallel to the trench on the oceanic plate that is not subducting. The diagram also shows the lithosphere and asthenosphere, with the lithosphere being the rigid outer layer of the Earth and the asthenosphere being the more fluid, underlying layer that the lithospheric plates move on.

This image provides a clear representation of how ocean-to-oceanic plate convergence leads to the creation of trenches and volcanic island arcs, key features in understanding plate tectonics and the dynamic processes that shape the Earth's surface.

Figure 9.2.2 Features formed by the intrusion of plutonic igneous rock into preexisting country rock

The image illustrates a cross-sectional diagram of a pluton, showcasing magmatic structures within it, with both concordant and discordant contacts. At the top, the diagram shows "country rocks," which are the surrounding older rocks into which the pluton has intruded. The boundary between the country rocks and the pluton is irregular, reflecting the complex interactions between the intruding magma and the existing rocks.

The pluton itself is depicted in pink, with several notable features. "Xenoliths," or fragments of country rock that have been incorporated into the magma, are scattered throughout the pluton. These xenoliths represent pieces of the surrounding rock that were not completely melted by the intruding magma.

Also present are "mafic enclaves," which are darker, denser portions of the pluton, possibly representing earlier or more mafic (rich in magnesium and iron) magmas that were mingled with the main body of the pluton.

"Schlieren," shown as dark streaks or lines within the pluton, represent elongated, lens-shaped concentrations of minerals that form due to the movement and flow of magma. These schlieren often indicate the direction of magma flow and can provide clues about the dynamics of the magma chamber.

Above the pluton, a "roof pendant" is depicted, which is a portion of the overlying country rock that has been left suspended within the magma chamber as the surrounding magma solidified.

Finally, a "stock" is shown on the right side of the diagram, representing a smaller, cylindrical body of intrusive rock that has been fed by the main pluton.

This diagram highlights the complexity of magmatic processes and the variety of features that can form within a pluton as it interacts with the surrounding country rocks.

Figure 9.2.3 Mt. Morrison roof pendant visible from Convict Lake

The image shows a serene mountain landscape at sunset, with a calm lake in the foreground that perfectly reflects the surrounding scenery. The water is still, mirroring the rocky shoreline composed of large boulders that extend into the water, creating a natural barrier. The mountains in the background rise steeply, with rugged, angular peaks that are bathed in a soft, pinkish-purple light from the setting sun. The cliffs of the mountains show a mix of gray, brown, and white tones, highlighting the geological layers and textures. Sparse vegetation can be seen on the slopes, and a few trees are visible along the shoreline, adding subtle green and yellow hues to the otherwise rocky landscape. The sky above is clear, with a subtle gradient from the light of the sunset, creating a tranquil and almost ethereal atmosphere. The reflection in the lake captures the entire scene, doubling the beauty of the rugged mountain backdrop.

Figure 9.2.4 An exotic terrane attached to subducting oceanic crust approaching the continent

The image is a diagram illustrating the geological process of terrane accretion, where fragments of the Earth's crust are added to a tectonic plate at a convergent boundary. On the left side of the diagram, an "Incoming Terrane" is approaching the boundary. This terrane is part of the oceanic crust, moving towards the continent. As it approaches, it encounters an "Active Accretionary Wedge," which is a mass of sediment that has accumulated and is being scraped off the oceanic plate as it subducts beneath the continental plate.

To the right of the accretionary wedge, an "Active Volcanic Arc" is shown. This volcanic arc forms as a result of the subduction process, where the oceanic plate is forced down into the mantle, causing melting and the rise of magma, leading to volcanic activity. The volcanic arc is depicted with active volcanism, including an erupting volcano.

Moving further to the right, the diagram shows an "Older Accreted Terrane," which is a previously accreted fragment that has become part of the continental crust. This terrane is shown as more stable, with vegetation growing on it, indicating that it is no longer tectonically active.

Next, a "Suture Zone" is depicted, representing the boundary where the older accreted terrane has joined the "Older Part of the Continent." This zone marks the location of the collision and welding of the terrane to the continental margin.

To the right of the suture zone, the "Extinct Volcanic Arc" is illustrated, representing an older volcanic arc that formed during a previous subduction event. This arc is no longer active, and its remnants have become part of the continental crust, covered with layers of sediment and vegetation.

Finally, the diagram ends with the "Older Part of the Continent," which is a stable, long-established portion of the continental crust, showing little to no tectonic activity and covered with a thick layer of soil and vegetation. The diagram as a whole demonstrates the dynamic process of terrane accretion, where pieces of the Earth's crust are gradually added to continents over geological time scales.

Figure 9.2.5 Major exotic terranes of the northern Sierra Nevada province

The image is a geological map of a section of the Sierra Nevada region, illustrating the distribution of various geological formations and terranes. The map uses different colors to represent specific geological units and features. The olive green color represents the Middle to Late Jurassic Arc Sequence, which consists of rocks formed during the Middle to Late Jurassic period, associated with volcanic and sedimentary processes of that era. This sequence is primarily found in the western portion of the map. The dark green color represents the Jura-Triassic Arc Belt, composed of rocks formed during the Jurassic and Triassic periods, also associated with volcanic activity. This belt lies adjacent to the Middle to Late Jurassic Arc Sequence. The brown color indicates the Calaveras Complex, consisting of a mix of volcanic, sedimentary, and metamorphic rocks. It is positioned further east and is a significant geological feature in the Sierra Nevada region. The navy blue color represents the Feather River Terrane, characterized by metamorphic rocks and forming part of the larger Sierra Nevada geological structure. This terrane occupies the northeastern part of the map. The teal color marks the Northern Sierra Terrane, another distinct geological unit within the Sierra Nevada, consisting of older metamorphic and igneous rocks. It occupies the northeastern part of the map. The maroon or red color represents the Sierra Nevada Batholith, a large, intrusive body of igneous rock that underlies much of the Sierra Nevada. This batholith forms the core of the Sierra Nevada mountains and is a prominent feature on the map.

Key locations such as Downieville, Alleghany, Grass Valley, and Confidence are marked on the map, along with the Mother Lode, Melones Fault, and Bear Mountain Fault. These faults and terranes are crucial to understanding the complex geological history and structure of the Sierra Nevada region. The map provides a visual representation of the different geological components that make up this area, illustrating the relationship between various terranes and fault lines.

Figure 9.2.6 Chlorite schist like that found in the Shoo Fly Complex

The image depicts a sample of chlorite schist from the Shoo Fly Complex. Chlorite schist is a type of metamorphic rock that is characterized by its foliated texture, meaning the minerals are aligned in layers or bands, giving the rock a distinct layered appearance. The rock sample in the image exhibits a range of greenish hues, typical of chlorite minerals, which are a major component of this rock type. The surface of the rock shows the fine-grained, sheet-like layers that are a hallmark of schist, with some areas appearing more coarse or rugged due to the presence of larger mineral grains or inclusions. The texture and color variations on the rock's surface reflect the complex geological processes that have acted upon the original material, transforming it into the metamorphic chlorite schist seen here. The label attached to the rock, marked with the number "150," indicates its identification within a collection, possibly for educational or research purposes. This chlorite schist is part of the Shoo Fly Complex, a geologically significant formation within the Sierra Nevada region, known for its diverse and complex rock types, which have undergone extensive metamorphism and deformation over geological time.

Figure 9.2.7 Map showing plutons and accreted terranes of the Sierra Nevada, California

The image is a geological map of a region in Northern California, showing various geologic units and structures with different colors and patterns to represent different rock types and ages. The map is oriented with north at the top and includes a scale bar in kilometers for reference.

On the left side of the map, the Great Valley Alluvium is shown as a broad band stretching from the north to the south of the map. This region is depicted in light gray, representing the unconsolidated sedimentary deposits that fill the Central Valley. To the west of this alluvium, the Coast Ranges are illustrated with various shades of green and yellow. These colors indicate different geological units, such as the Franciscan Complex, a highly deformed and metamorphosed suite of rocks that are part of an accretionary wedge. The San Andreas Fault is prominently marked with a thick black line running through the Coast Ranges, separating different blocks of geological formations.

To the east of the Great Valley Alluvium, the Sierra Nevada foothills and mountains are represented by a range of colors, including purples, browns, and reds, indicating a variety of rock types, including metavolcanic, metasedimentary, and granitic rocks. These colors correspond to different geological terranes, such as the Sierra Nevada Batholith, the Smartville Complex, and the Shoo Fly Complex. The map also shows several major fault lines, including the Melones Fault, which runs parallel to the eastern edge of the map.

The map provides a detailed view of the complex geology of this region, highlighting the interactions between different geological terranes, fault systems, and the processes that have shaped the landscape over millions of years.

Figure 9.2.8 Generalized map showing the Kings River ophiolite

The image is a detailed petrotectonic unit map of the Kings-Kaweah ophiolite belt in central California, depicting various geological formations and structures. The map includes a legend that explains the colors and patterns used to represent different rock types and ages, as well as tectonic features.

The map is oriented with north at the top and covers a region that includes Fresno and the surrounding areas, particularly focusing on the Kings River and Kaweah River regions. The map is divided into various geological units, each represented by different colors and patterns.

The legend indicates that the light gray color represents the Early Cretaceous Sierra Nevada batholith, which includes rocks such as gabbro, diorite, tonalite, and granodiorite. The green areas on the map represent the Foothills Metamorphic Belt, which includes several different formations such as the Late Jurassic Owens Mountain complex (depicted in dark green) and the Middle to Late Jurassic Mill Creek intrusive complex (shown in a lighter green).

Other significant units include the Permo-Carboniferous Kaweah serpentinite mélange, represented by a dotted pink pattern, and the Early Ordovician Kings River ophiolite, depicted in a pink color. These formations are associated with complex tectonic processes, including the accretion of oceanic crust onto the continental margin and subsequent deformation and metamorphism.

The map also includes the locations of major rivers, such as the Kings and Kaweah Rivers, and major roads, including Highways 180 and 198. Additionally, there is an inset map in the upper right corner showing the regional context within central California, including the location of the map area relative to the Sierra Nevada Batholith (SNB) and the San Andreas Fault.

Overall, the map provides a comprehensive view of the geological history and structure of the Kings-Kaweah ophiolite belt, highlighting the diverse rock types and tectonic features that have shaped this region over hundreds of millions of years.

Figure 9.2.9 A zoomed in and generalized map showing the Kings River ophiolite

The image is a detailed geological map of the area surrounding Pine Flat Lake, Kings River, and nearby mountain ranges such as Dalton Mountain and Bald Mountain. The map provides a visual representation of various rock units, structural features, and geological formations, along with a comprehensive legend explaining the colors and patterns used to represent different geological entities.

The map is oriented with north at the top and covers a region that includes Pine Flat Lake, Hughes Mountain, and the Mill Creek Valley. The legend in the upper right corner of the image describes the different geological units and their corresponding colors. The map shows that the area includes several significant geological formations. The Early Cretaceous tonalite, pyroxene quartz diorite, and hornblende gabbro of the Sierra Nevada batholith are shown in light gray. These are some of the oldest rocks in the region and form the core of the Sierra Nevada range. The Middle to Late Jurassic Mill Creek intrusive complex, represented by a complex pattern of light green, pink, and brown colors, includes a mixture of diorite, gabbro, and leucotonite dikes, as well as volcaniclastic sediments and metamorphic rocks. The Permian to mid-Triassic Calaveras complex, shown in purple, consists of bedded radiolarian chert, siliceous argillite, and chaotic chert-argillite mélange with subordinate siliciclastic and volcaniclastic turbidites and marble lenses. The Early Ordovician Kings River Ophiolite (KRO), depicted in dark brown with a distinctive texture, includes pillow basalts, sheeted dikes, layered clinopyroxenite, troctolite, and rare cherts, representing a portion of the ancient oceanic crust that was accreted onto the continent during tectonic collisions. The Permo-Carboniferous Ductile Shear Zones and Mélange, shown in red with a distinct pattern, contain metabasite, meta-chert, and metaperidotite blocks within a serpentinite matrix, indicative of significant tectonic activity and deformation.

The map also highlights several key structural features, such as oceanic mantle ductile shear zone extensions, strong constrictional fabrics, and steeply dipping crustal sections. These features are important in understanding the tectonic evolution of the region and the processes that have shaped the Sierra Nevada and surrounding areas. Overall, the map provides a detailed and informative view of the complex geological history of this part of California, illustrating the relationships between different rock units and the tectonic forces that have influenced the region over hundreds of millions of years.

Figure 9.3.3 Subduction and Volcanic Arc

This image illustrates a detailed cross-sectional view of a subduction zone, where an oceanic plate is being forced beneath a continental plate. The image shows the different layers and structures associated with this tectonic process. The oceanic crust, shown on the left, moves towards the continent and descends into the Earth's mantle at an ocean trench, marked by a deep groove in the seafloor. As the oceanic crust is subducted, it enters the lithosphere, the rigid outer part of the Earth, which includes the crust and upper mantle. The subducting slab pushes into the asthenosphere, a more ductile layer of the mantle below the lithosphere, where it begins to melt due to the increasing pressure and temperature.

The image also highlights the creation of an accretionary prism, which forms from sediments scraped off the subducting plate and accreted onto the edge of the overriding continental plate. Above this zone, a volcanic arc is shown forming on the surface of the continental crust, fed by magma generated from the melting of the subducting slab. The magma rises through the lithosphere, accumulating in magma chambers, and eventually reaching the surface to form volcanoes.

The Moho discontinuity, which marks the boundary between the Earth's crust and the mantle, is also illustrated. This boundary is crucial for understanding the difference in material properties and seismic behavior between the crust and the underlying mantle. Additionally, the image depicts rising diapirs, blobs of less dense material that ascend through the lithosphere from the mantle, contributing to the complex processes within the subduction zone. Overall, this cross-section provides a comprehensive view of the dynamic and interconnected processes occurring at a convergent plate boundary.

Figure 9.3.4 Exfoliation jointing, or sheeting, on Half Dome in Yosemite National Park

This image depicts the iconic Half Dome in Yosemite National Park, California, a massive granite rock formation known for its distinct shape, resembling a giant dome that appears to have been cleaved in half. The smooth, rounded side is contrasted by the steep, vertical face on the opposite side, which towers above the valley floor. The rock surface is a light gray, characteristic of the granite that forms much of the Sierra Nevada mountains.

A significant geological feature visible in the image is the process known as exfoliation jointing or sheeting. This process involves the peeling away of outer layers of rock, much like the layers of an onion, due to the reduction of pressure as overlying material is eroded away. In the case of Half Dome, these exfoliation joints are evident in the form of parallel, curved cracks and fractures that follow the contours of the dome. These joints create the appearance of horizontal layers, which can be seen clearly near the summit and along the steep faces of the formation. The sheeting results in large, slab-like sections of granite that eventually break off and fall, contributing to the smooth, rounded shape of the dome over time.

Visible in the image are the cables used by hikers to ascend the final steep section of the dome, a popular but challenging route. The cables are affixed along a narrow, steep path that climbs toward the summit, illustrating the scale and difficulty of the ascent. In the foreground, a few resilient pine trees cling to the rocky surface, adding a touch of greenery against the stark, towering rock. The bright blue sky overhead provides a clear and vibrant backdrop, emphasizing the sheer height and majesty of Half Dome as it rises dramatically from the surrounding landscape.

This scene captures not only the awe-inspiring natural beauty and the geological grandeur that make Half Dome a symbol of Yosemite but also the dynamic geological processes like exfoliation that continue to shape this iconic formation, making it a destination for adventurers and nature lovers alike.

Video 9.3.1 Half Dome Flyover

The video provides a dynamic flyover of Half Dome, an iconic granite formation located in Yosemite National Park. The camera starts from the northwest, gradually approaching Half Dome, showcasing its imposing height and the smooth, curved face that has been sculpted by geological processes over millennia. As the perspective shifts, the viewer is taken around the southeast side of the dome, offering a sweeping view of the dramatic drop-offs and the surrounding landscape.

As the flyover continues, the video highlights the exfoliation jointing, or sheeting, on the surface of Half Dome. This geological feature is characterized by large, curved slabs of rock peeling away from the main granite body, much like layers of an onion. These layers are a result of the release of pressure from overlying rock, causing the granite to expand and fracture in a series of concentric sheets. The video captures these joints in detail, emphasizing the rounded, stair-like appearance they give to the surface of Half Dome, which is particularly visible as the camera loops around the formation, providing a close-up view of the intricate patterns formed by the exfoliation process. The video concludes by pulling back to reveal the full majesty of Half Dome in its natural setting, framed by the surrounding wilderness of Yosemite.

Figure 9.4.1 Large Gold Nugget (Placer Gold) From California

The image displays a large, naturally formed gold nugget against a black background. The nugget has a rough, irregular surface with a slightly flattened shape, showcasing the distinctive luster and bright yellow color characteristic of pure gold. The surface appears uneven with various indentations, which are typical of gold nuggets as they are shaped by natural processes such as erosion and weathering over time. This nugget likely formed over millions of years as gold-rich water deposited tiny particles of the metal into a larger mass. The image effectively highlights the texture and brilliance of the gold, making the nugget a striking example of native gold in its natural form.

Figure 9.4.2 Calaverite Sample

The image shows a piece of rock with visible gold veins running through it. The rock is primarily composed of a pale purple to lavender-colored fluorite, which serves as the host for the bright yellow gold that appears in irregular, branching patterns across its surface. The contrast between the dull, opaque fluorite and the shiny, metallic gold makes the veins stand out prominently. The gold appears to be embedded within the fluorite, indicating it was deposited within the rock during the mineralization process. This type of specimen is typical of fluorite veins where gold is often found in hard rock mining environments. The rock is placed against a wooden background, which provides a neutral contrast to the vivid colors of the fluorite and gold.

Figure 9.4.3 Placer Gold Flakes

The image displays a pile of finely crushed gold flakes spread out on a light-colored surface, possibly paper or fabric. The flakes are irregular in shape, with a bright yellow color typical of pure gold. These flakes vary in size but are generally small, with some almost appearing as dust while others are slightly larger. The overall texture of the pile gives the impression of a shimmering mass due to the reflective properties of the gold, which catches the light and highlights the individual flakes' glossy surfaces. The light background enhances the brightness of the gold, making the pile stand out prominently. This type of gold is often referred to as "placer gold" and is commonly found in alluvial deposits, where gold particles accumulate after being eroded from larger veins.

Figure 9.4.4 Gold Bearing Quartz from the Mother Lode, CA

The image shows a specimen of gold-bearing quartz from the Mother Lode region. The quartz, which appears as a white, translucent mineral, is the host rock that contains visible streaks and patches of gold. The gold is seen as bright yellow metallic flecks and veins interspersed throughout the quartz, contrasting with the white background. Additionally, areas of the specimen have dark, almost black mineralization, which could be associated sulfide minerals that are commonly found alongside gold in quartz veins. The overall appearance highlights the rich, natural occurrence of gold within its host quartz matrix, a characteristic feature of the Mother Lode gold deposits.

Figure 9.4.5 Tectonic Setting of Most Common Gold Deposits

The image is a geological cross-section diagram illustrating the formation of various mineral deposits in different tectonic settings. It is divided into distinct regions, each labeled according to its tectonic environment and associated mineralization processes.

On the left side of the diagram is the continent, representing the continental crust. This region features labels indicating the presence of Epithermal Au (gold) deposits. Adjacent to the continent is the oceanic arc, which represents a volcanic arc formed by subduction. It shows deposits of Epithermal Au, VHMS (Volcanogenic Massive Sulfide) Cu-Au, and Porphyry Cu-Au (skarns).

Positioned behind the volcanic arc is the back arc area, characterized by extensional tectonics and containing VHMS Cu-Au and Porphyry Cu-Au (skarns) deposits. Further inland on the continent, the continental arc section shows Epithermal Au and Porphyry Cu-Au (skarns) deposits. The accreted terranes region represents terrains that have been accreted to the continent, featuring Orogenic Au deposits.

At the far right, the back arc extension region indicates extensional tectonics behind the arc, featuring Epithermal/Hot Spring Au and Carlin-style Au deposits.

Below the cross-section, a legend explains the various geological features depicted in the diagram. The accretionary wedge is represented in dark brown, indicating the accumulation of sediments and oceanic crust.

Figure 9.4.6 Venting Black Smoker

The image depicts a hydrothermal vent located on the ocean floor. In the center of the image, there is a venting chimney emitting dark, smoky plumes of mineral-rich fluids. These fluids are released into the surrounding water, creating a dense cloud of black smoke due to the high concentrations of sulfide minerals.

Surrounding the vent, the ocean floor is covered with vibrant red and white tube worms, indicating a thriving biological community. These tube worms rely on the chemicals released by the vent for their energy source, forming a symbiotic relationship with chemosynthetic bacteria.

In the upper part of the image, equipment and cables are visible, indicating the presence of scientific instruments used to study the hydrothermal vent. On the right side, a diver or remotely operated vehicle (ROV) can be seen, providing a sense of scale and highlighting the efforts to explore and understand these unique underwater ecosystems. The overall scene captures the dynamic interaction between geological activity and biological life at hydrothermal vent sites.

Figure 9.4.7 The Origin of Placer Gold Deposits

The image is a black-and-white diagram titled "Origin of Placer Gold." It illustrates the geological process through which gold becomes concentrated in streambeds. The diagram shows mountainous terrain labeled "Mother Lode," where gold is embedded in quartz veins. Over time, the gold is liberated through weathering and erosion, eventually being carried down into streams. As the stream flows downhill, the heavier gold particles settle out of the water when it slows down, particularly around rough areas in the streambed and as the water flows around bends. This settling of gold particles in the streambed leads to the formation of placer gold deposits.

Figure 9.4.8 1852 miners in California work their "long tom" to separate gold from gravel

The image is an old black-and-white photograph from 1852, depicting miners in California working at a mining site. The focus is on a group of four miners engaged in using a "long tom" to separate gold from gravel. In the foreground, two miners are actively working, one holding a shovel and the other standing near the long tom, a trough-like structure used in gold mining. The long tom is filled with gravel, which is being washed by water to separate out the gold. Behind them, a third miner is sitting on a wooden cart pulled by a horse, which is waiting nearby. The scene is set in a rural, hilly area with some trees and vegetation in the background, capturing a moment from the Gold Rush era, highlighting the labor-intensive process of gold mining during that time.

Figure 9.4.9 Index Map of 1968 Placer Deposits in Nevada County, CA

The image is a black-and-white map of Nevada County in California, highlighting its river systems and neighboring areas. The map outlines Nevada County, showing its location in relation to surrounding regions and notable geographic features.

Key locations such as Nevada City, Oroville, Marysville, Auburn, and Placerville are marked with circles. The map also depicts the main rivers and their forks, including the Yuba River (with its North, Middle, and South Forks), Bear River, Feather River, and American River. The North, Middle, and South Forks of the Yuba River are shown converging towards Nevada City, with the South Fork being prominently highlighted.

The map includes a hatched area around Nevada City, indicating a specific region of interest. A small inset in the upper right corner shows a simplified outline of California, with the area of the main map marked for context. Additionally, the map scale is provided at the bottom, showing distances of 10, 20, and 30 miles.

Prominent towns such as Yuba City and Sacramento are also labeled, showing their locations relative to Nevada County. Lake Tahoe is marked to the east, just outside the county's boundary. The map uses dashed lines to delineate county boundaries and major geographic features, providing a clear and detailed representation of the area.

Figure 9.4.10 Acid mine drainage into Spring Creek, in Shasta County

The image shows an aerial view of a site where acid mine drainage is flowing into Spring Creek, California. The landscape appears dry and rugged, with a mix of sparse vegetation and exposed earth. A narrow stream, heavily stained with orange and yellow hues from the acidic water and iron deposits, runs through the center of the image. The vibrant colors are a result of the chemical reactions between the acidic water and minerals, which are common in areas affected by mining activities. The surrounding area includes steep, eroded slopes, indicating the impact of both natural and human activities on the landscape. The road at the top left of the image suggests that the site is near a developed area, but the environmental damage from the acid mine drainage is evident, highlighting the ecological challenges posed by abandoned or improperly managed mining sites.

Figure 9.4.11 Hydraulic Mining, CA, 1870s

The black-and-white photograph depicts a scene of hydraulic mining, a method used during the California Gold Rush. The image shows powerful jets of water being directed at a mountainside to dislodge large volumes of earth and rock. These water jets, emerging from several high-pressure hoses, arc through the air, creating a misty spray.

In the foreground, a wooden structure resembling a flume or sluice can be seen, which was used to channel water and washed material. Several men are standing on the rocky ground, indicating the scale of the operation. The background reveals a steep, eroded cliff face, highlighting the significant environmental impact of hydraulic mining.

The overall scene illustrates the intensity and scale of hydraulic mining operations, where large amounts of water were used to extract gold from sediment. The method involved washing away entire hillsides to access gold deposits, which caused substantial changes to the landscape and had long-term environmental consequences.

Figure 9.4.12 CA Gold Mines by Type and Status, 1995-2023

This map illustrates the locations and statuses of gold mines in California from 1995 to 2023. It features a satellite image of Northern California, overlaid with symbols indicating the type and status of gold mines. The map is framed with geographical coordinates and includes a compass rose in the upper left corner for orientation.

The legend in the lower left corner explains the symbols used on the map. Red circles represent abandoned lode gold mines, yellow circles represent active placer gold mines, red crosses signify active lode gold mines, and yellow crosses denote abandoned placer gold mines. The Sierra Nevada Province is outlined in blue, providing context for the geological setting of many of these mines.

The map highlights several clusters of gold mines, particularly in the regions of the Sierra Nevada and Northern California. Significant concentrations of active and abandoned mines are visible around Shasta National Forest, Lassen National Forest, and Tahoe National Forest. The inset in the upper right corner offers a broader view of the map's coverage area within California, indicating the Sierra Nevada Province's location relative to major cities such as San Francisco and Los Angeles.

This visual representation helps to understand the distribution and historical activity of gold mining within the state, showcasing both the enduring legacy of the Gold Rush era and the ongoing exploration and extraction efforts.

Figure 9.5.1 South Inyo Crater Lake near Mammoth, CA

The image depicts Inyo Crater Lake, located near Mammoth, California. The crater is a circular depression with steep, rocky walls composed of volcanic material. The slopes leading down to the lake are strewn with loose rocks and boulders, indicating the volcanic origin of the crater. The lake itself is a serene, turquoise body of water that fills the bottom of the crater, contrasting vividly with the darker, rugged terrain surrounding it. Dense forests of coniferous trees surround the crater, with tall pine trees dominating the landscape. In the background, the peaks of the Sierra Nevada mountains are visible, partially obscured by a hazy sky. The scene captures the natural beauty and geological significance of the area, with the crater being a remnant of past volcanic activity in the region.

Figure 9.5.2 Obsidian Dome near Inyo Craters

The image shows the rugged terrain of Obsidian Dome, located near Inyo Craters in California. The foreground is filled with loose, angular boulders and rocks that are dark in color, likely volcanic in origin. The steep slope leads up to a jagged ridge of volcanic rock. The sun is positioned just above the ridge, casting bright rays of light and creating a lens flare effect across the image. The intense sunlight highlights the rough texture of the rock formations, adding depth and contrast to the scene. The sky is clear, with a deep blue hue that emphasizes the harsh, exposed nature of the landscape. The overall atmosphere is one of stark beauty and raw geological power, characteristic of the volcanic features in this region.

Figure 9.5.3 Snowflake Obsidian Sample from Obsidian Dome

The image shows a close-up view of a piece of snowflake obsidian, a type of volcanic glass, being held in someone's hand. The obsidian is dark black with a glossy, glass-like texture, characteristic of this material. Scattered across the surface of the obsidian are small, white, snowflake-like patterns, which give this particular variety of obsidian its name. These snowflake patterns are formed by the crystallization of the mineral cristobalite within the volcanic glass as it cools. The hand holding the obsidian is positioned in such a way that the viewer can see the texture and detail of the rock clearly, with sunlight highlighting the contrast between the black obsidian and the white snowflakes. The background suggests an outdoor setting, likely at the site where the obsidian was found, such as Obsidian Dome in California. The surrounding environment, partially visible in the background, includes vehicle components, suggesting that this piece of obsidian was collected or observed during fieldwork or a visit to the volcanic site.

Figure 9.5.4 Schematic Illustrations of the Formation of Inverted Topography

The image consists of three diagrams that illustrate the process of inverted topography formation over time. The first diagram, labeled "At Eruption," shows a volcanic landscape immediately after an eruption. A volcano is depicted with a dark-colored lava flow extending from its base down the slope. This lava flow has solidified and now sits atop the surrounding terrain, which is lighter in color, likely representing loose volcanic ash or tephra. The landscape at this stage has a typical volcanic profile, with the lava flow lying lower in the landscape compared to the surrounding, higher areas.

The middle diagram represents an intermediate stage in the formation of inverted topography. Over time, the softer surrounding materials, such as ash and tephra, begin to erode away due to weathering and other natural processes. As a result, the lava flow, which is more resistant to erosion, starts to stand out more prominently as the surrounding landscape is worn down. The previously lower-lying lava flow is now becoming more elevated relative to the eroding landscape around it.

The final diagram, labeled "Today," depicts the present-day landscape after significant erosion has taken place. The formerly low-lying lava flow has now become a raised, flat-topped ridge or mesa, while the surrounding softer materials have been almost entirely eroded away. This results in what is known as inverted topography, where the once lower-lying lava flow is now a prominent elevated feature in the landscape, and the former higher terrain is now at a lower elevation. The diagrams effectively show the transition from a typical volcanic landscape to one where the more resistant lava flow becomes an elevated ridge due to the differential erosion of the surrounding softer materials, illustrating the concept of inverted topography.

Figure 9.5.5 Looking Southeast from Pincushion Peak towards Big Table Mountain

The image shows a view from Pincushion Peak looking southeast towards Big Table Mountain in Madera County, California. The landscape is characterized by rolling hills covered in lush green vegetation, indicative of a typical springtime scene in the region. In the foreground, scattered rocks and a few trees, some of which appear to be affected by fire or disease, dot the grassy terrain. The middle ground reveals a calm body of water, likely a reservoir or small lake, nestled between the hills. The water level is visibly lower, with a distinct lighter-colored band of exposed shoreline encircling it, suggesting a recent drop in water levels.

In the background, Big Table Mountain stands out as a prominent, flat-topped mesa, a result of the area's unique geologic history involving volcanic activity. The steep cliffs of the mesa are partially covered with trees, and the overall landscape is framed by a sky with light, wispy clouds. The scene captures the serene beauty of the Sierra Nevada foothills, where natural features like mesas and valleys are sculpted by the forces of erosion and volcanic activity.

Figure 9.5.6 Aerial Imagery Showing Big Table Mountain in Fresno and Madera Counties, CA

The aerial imagery shows Big Table Mountain, located in Fresno and Madera Counties, California. The view captures the distinct topography of the region, highlighting the rugged, undulating terrain. The image is dominated by the presence of Millerton Lake, whose deep blue waters contrast sharply with the surrounding dry, brown hills. The lake's irregular shape forms several inlets and peninsulas, including the prominent Pincushion Peak area, which juts out into the water.

Big Table Mountain is characterized by its long, flat-topped mesas, which stand out against the surrounding landscape. These mesas, outlined in yellow for clarity, are remnants of ancient lava flows that have resisted erosion, leaving behind these prominent features. The mesas are primarily covered in sparse vegetation, with some areas more densely forested, particularly along the northern edges.

To the southeast, near Marshall Junction, the terrain becomes less rugged, transitioning into more developed areas with visible roads, structures, and agricultural lands. The image also shows various points of interest labeled on the map, such as trailheads and ecological reserves, indicating the area's significance for recreation and conservation.

The overall view provides a comprehensive look at the geological and topographical features of Big Table Mountain, showcasing its unique formation and the way it dominates the landscape in this part of California.

Figure 9.5.7 Devils Postpile

The image shows a striking geological formation, characterized by vertical, columnar basalt structures known as columnar jointing. These columns appear as tall, hexagonal pillars of rock, rising vertically from the ground. The formation is prominently featured on a hillside, with the columns creating a ribbed effect along the slope.

In the foreground, there is a field of large, angular rocks and boulders, likely fragments that have broken off from the main basalt columns over time. The rocky ground gradually ascends towards the middle ground, where the columns begin.

Above the columns, the landscape transitions into a more vegetated area. The top of the hill is dotted with tall pine trees, adding a contrasting element of greenery to the gray and black tones of the basalt columns. These trees are scattered, some standing alone while others form small clusters.

The sky above is clear and blue, with no visible clouds, indicating a sunny day. The overall scene combines the ruggedness of the basalt columns with the natural beauty of the pine trees, showcasing a unique intersection of geological and botanical elements.

Figure 9.5.8 Diagram Showing the Formation of Columnar Jointing

The image illustrates the process of columnar jointing formation, which occurs in cooling lava or magma. The diagram shows three hexagonally shaped columns that represent the jointing pattern typical of this geological phenomenon. The top of the columns is labeled as a "Cold Surface," indicating that this is where cooling begins.

As the surface cools, it contracts, causing the rock to fracture. The arrows pointing inward towards the center of each hexagon illustrate this contraction process. The fractures propagate downward as the cooling and contraction continue, eventually forming the characteristic hexagonal columns seen in columnar jointing.

The left side of the image is labeled with "Hotter" at the bottom and "Cooler" at the top, highlighting the temperature gradient from the hot, cooling lava or magma below to the cooler surface above. The right side of the image indicates "Fracture Propagation" with an arrow pointing downwards, showing how the fractures deepen as the cooling process advances.

Overall, the diagram effectively demonstrates how the contraction of cooling lava or magma leads to the formation of these distinct hexagonal columns, a process commonly observed in places like the Giant's Causeway in Northern Ireland and Devil's Postpile in California.

Figure 9.5.9 On Top of Devils Postpile

The image depicts a close-up view of a basaltic formation with a distinct hexagonal pattern, characteristic of columnar jointing. The hexagonal basalt columns are arranged in a tightly packed pattern, creating a tiled appearance on the ground's surface. The columns are slightly raised and uneven, with some sections appearing more weathered than others, resulting in a textured surface.

In the background, the image transitions into a wooded area with tall pine trees. These trees are scattered and cast shadows over the basaltic formation, adding depth to the scene. Beyond the immediate area of the columns, a forested valley is visible, showcasing a variety of vegetation and rugged terrain. The distant cliffs and rock faces add to the dramatic natural landscape.

The overall scene combines the unique geological structure of the basalt columns with the lush greenery of the pine forest, illustrating the interplay between geological formations and the surrounding natural environment.

Figure 9.6.1 Anatomy of a Glacier

The image depicts the anatomy of a glacier and explains the concept of the glacier budget, which is the balance between the accumulation and ablation of ice within a glacier. The diagram is divided into two primary zones: the Accumulation Zone and the Ablation Zone.

On the left side of the image, the Accumulation Zone is shown near the top of the glacier, where snowfall and ice formation occur. Snowfall accumulates, and as it compresses over time, it transforms into glacial ice. The right inset of the diagram provides a detailed explanation of this process, showing the transition from loose, fluffy snow (containing about 90% air) to granular ice, then to firn (with 50% air), and finally into dense glacial ice with about 20% air as bubbles. The downward arrows in the Accumulation Zone represent the accumulation of snow and ice.

As the glacier moves downward, it reaches the Ablation Zone, where ice loss occurs due to several processes. Sublimation, which is the direct transformation of ice into water vapor, is represented by the upward arrows. The diagram also shows the melting of ice and the calving of icebergs, where chunks of the glacier break off into the ocean.

The glacier budget is determined by the balance between these two zones. If accumulation exceeds ablation, the glacier will advance; if ablation exceeds accumulation, the glacier will retreat. The text at the bottom of the diagram summarizes these points, indicating that glaciers gain mass from snowfall in the Accumulation Zone and lose mass in the Ablation Zone due to melting, iceberg calving, and sublimation. The diagram visually represents these processes to provide a comprehensive understanding of how glaciers form, move, and lose ice.

Video 9.6.1: Glaciation and Hanging Valleys Formation

This Interact educational resource describes how hanging valleys are formed through a long period of glacial history. It is an educational resource produced by Tom State University for Interact, Wicked Weather Watch, University Arctic and EduArctic. During the last ice age, which ended about 10,000 years ago, much of the north was covered in ice sheets, such as that that can be seen in the distance.

These ice sheets had outlets in glaciers that flowed under the force of gravity down through the mountain valleys, many into the sea. In this case, we are stood above the glacier looking to the ice sheet which accumulates snow, and behind us the mouth of the glacier reaches much further behind us. It's snowing to denote that this is a cold period, but of course it snows every year in the north.

As well as the accumulation of ice and snow in the glacier and the ice sheet in the valleys, we have small ice caps and areas of snow on the mountain tops. Some mountain tops, however, are clear of snow and ice and these are called nunnitacks. These nunnitacks were important habitats in previous cold periods for the survival of plants.

During a warm period, such as 10,000 years ago or now, the snow accumulation decreases and the glacier and ice sheet start to lose volume and the glacier starts to retreat along the valley from behind us until it's in front of us and we can see the snout of the glacier retreating into the background. At the same time, the mountain glacier on the right-hand side starts to lose volume and disconnects with the glacier in the valley below. At the tops of the mountains, frost works on rocks to shatter them, producing small materials and these are washed down the mountain slopes in gullies in the rocks and accumulate at the foot of the mountain slopes as alluvial fans.

During the past 10,000 years there have been many climate fluctuations with warm and cold periods. Here we see a cold period denoted by snow, although remember that the snow falls every year. During these cold periods the ice sheets accumulate more snow and ice and the glaciers flow again towards us and down the valleys and the connection between the hanging glacier on the right at the top of the mountain and the glacier at the bottom is established again.

In a renewed period of warming, the glacier of course starts to retreat again as we saw earlier on. This time you can see a moraine being left behind as the glacier retreats. This moraine marks a point at which the glacier terminated following the last advance.

These moraines are formed when materials, rocks sliding down the mountains, fall on the glacier and also from materials being pushed from the valley floor in front of the glacier and of course they're most visible when the glacier retreats and leaves them behind. During the warming process the hanging glacier or the mountain glacier has been disconnected from the glacier and the valley and now there is a hanging valley with a small lake in it and a waterfall down to the valley floor below. As the climate continues to warm the snow and ice disappear leaving the hanging valley with its lake and waterfall to the valley floor below.

Also vegetation starts to move in. Initially the grasses and herbs are established but later trees become established also and of course the land which has been without snow and ice for the longest have the most advanced vegetation of the forest. The sequence you have seen represents what has happened since the last ice age in an area for example like Scotland or the English Lake District or the Swedish Subarctic but of course we have only shown one advance and two retreats.

In practice there may have been very many in the 10,000 years that have been depicted in just a few moments. The finishing frame is what we see today but of course the sequence we've shown could depict what happens now and from now onwards to the high arctic area which is now glaciated much as the north of Britain would have been 10,000 years ago. So we have provided two scenarios.

One an animation of what we have seen over the past 10,000 years for areas which now look like this frame you are looking at but also areas of the high arctic which are now covered in ice and snow which could in some hundreds of years look like the frame we're looking at now. This has been an interact educational resource. The animation was developed by Vyacheslav Rudchenko of Tomsk State University and it was designed by Professor Terry Callaghan on behalf of Interact, the University of Arctic, Wicked Weather Watch and Eduarctic.

It had valuable input from Professor Perlmund of Stockholm University and Dr Kristi Jönsson of Uppsala University.

Figure 9.6.2 Glacial striations and polish near Lambert Dome

The image illustrates glacial striations, which are scratches or gouges cut into bedrock by glacial abrasion. These striations are formed when a glacier moves over a bedrock surface, dragging along rocks and debris embedded in the ice. The resulting linear grooves are indicative of the direction of the glacier's movement and can provide important information about past glacial activity.

In this particular image, the striations are clearly visible as linear features cutting across the bedrock surface. The patterns are typically parallel to each other and vary in depth and width, depending on the size of the debris and the force exerted by the moving glacier. Observing these striations helps geologists understand the dynamics of glacier flow and reconstruct the history of glaciation in a given area. The smooth, polished appearance of the rock surface alongside the striations further highlights the erosive power of glacial ice as it shapes the landscape.

Figure 9.6.3 Geologic History and Formation of Yosemite National Park

The series of images illustrates the formation of Yosemite Valley over geological time, depicting the transformation of the landscape through various stages of glacial activity.

The first image shows Yosemite Valley before significant glaciation, with steep granite walls and a deep, V-shaped valley typical of river erosion. Vegetation covers much of the valley floor and the surrounding mountains.

In the second image, the onset of glaciation is evident as glaciers begin to flow into the valley. The glaciers carve out the granite, deepening and widening the valley into a U-shape. The movement of the ice is marked by striations and moraines, indicating the powerful erosive forces at work.

The third image depicts the peak of glaciation, with the valley entirely filled with thick glacial ice. The glaciers continue to sculpt the granite, polishing and rounding the valley walls. This stage shows the maximum extent of glaciation, with ice flowing through the valley and over the surrounding highlands.

In the fourth image, the glaciers begin to recede, leaving behind glacial lakes and deepened valleys. The retreating ice reveals the U-shaped valley, now filled with glacial meltwater. The newly formed lakes are bounded by moraines and other glacial deposits, creating a dramatic landscape of water and rock.

The fifth image shows the post-glacial landscape of Yosemite Valley. The glaciers have fully retreated, leaving behind a wide, flat valley floor with remnants of glacial lakes and polished granite cliffs. The iconic features of Yosemite, such as Half Dome and El Capitan, stand prominently in the landscape, sculpted by the glacial activity. Vegetation begins to recolonize the valley, adding green to the stark granite and blue waters.

This sequence visually captures the dynamic processes of glaciation and deglaciation, highlighting the profound impact glaciers have had on shaping Yosemite Valley through time. The transformation from a river-carved valley to a glacially sculpted U-shaped valley showcases the power of natural forces in creating the dramatic and iconic landscapes we see today.

Figure 9.6.4 Yosemite from Tunnel View

The image showcases the iconic Tunnel View overlook in Yosemite National Park, providing one of the most famous and breathtaking vistas in the park. From this vantage point, you can see a panoramic view of Yosemite Valley, framed by towering granite cliffs and lush forests. On the left side of the image, El Capitan dominates the scene with its sheer vertical face, a favorite among rock climbers worldwide.

To the right, you can see Bridalveil Fall, known for its ethereal beauty as the water cascades down a 620-foot drop, often creating a delicate mist that resembles a bridal veil. In the distance, Half Dome rises majestically, its distinctive silhouette marking one of Yosemite's most recognizable landmarks. The valley floor below is covered with a dense forest of conifers, and during different seasons, the colors and lighting can dramatically change, enhancing the natural beauty of the landscape.

This view from Tunnel View is particularly famous for its ability to capture the essence of Yosemite's grandeur, often inspiring artists, photographers, and nature enthusiasts alike. The combination of geological wonders and natural beauty encapsulates the timeless allure of Yosemite National Park.

Figure 9.6.5 Glacial Extent and Direction of Ice Flow in Yosemite National Park

The image provides a detailed map of ice and glacier flow within Yosemite National Park, particularly focusing on the Tuolumne River region. The intricate patterns of glacial movement are depicted with arrows, indicating the direction and flow of the ice across the landscape. This map highlights the extensive glaciation that shaped Yosemite's topography over thousands of years.

You can see the vast ice fields and the paths they carved through the valleys and over the ridges. The Tuolumne River canyon, prominently featured in the center, is shown to have been heavily influenced by glacial activity, with the ice flows converging and diverging as they moved through the terrain. The arrows indicate the dominant flow directions, demonstrating how the ice would have moved from higher elevations to lower valleys, sculpting the granite and creating the dramatic landscape Yosemite is famous for today.

The map also includes elevation markers, providing a sense of the scale and vertical relief within the park. The detail of the glacial flows offers insight into the dynamic processes that have contributed to Yosemite's formation, illustrating the powerful forces of nature that continue to shape the park's environment. This visual representation of ice and glacier movement is a testament to the geological history of Yosemite, showing the enduring impact of glaciation on its stunning landscapes.

Figure 9.6.6 Repeat Photography of the Lyell Glacier

The comparison of photographs from 1883 and 2022 of the Lyell Glacier in upper Yosemite vividly demonstrates the dramatic retreat of the glacier over the past century.

In the 1883 photograph, the glacier appears robust and expansive, covering a significant portion of the rocky terrain with a thick layer of ice and snow. The glacier extends down from the peaks, filling the valleys and creating a continuous ice field.

By contrast, the 2022 photograph shows a drastically different scene. The once-mighty glacier has significantly receded, with only small remnants of ice clinging to the higher elevations. The valley floor, previously covered by the glacier, is now exposed, revealing bare rock and glacial deposits. The dramatic reduction in the glacier's size highlights the impact of climate change and warming temperatures on glacial landscapes.

This repeat photography underscores the importance of monitoring and understanding glacial dynamics, as glaciers are critical indicators of climate change. The stark contrast between the two images serves as a visual testament to the ongoing and accelerating changes in our natural environment.

Figure 9.7.1 Examples of Some Types of Mass Wasting

The image illustrates various types of mass movements and landslides, which are classified based on their movement mechanisms and the materials involved.

At the top left, Figure A depicts a rotational landslide, which occurs when a mass of earth or rock moves down a slope along a curved surface, causing the sliding mass to rotate backward. This type of landslide often leaves a concave scar on the slope.

Figure B shows a translational landslide, where the sliding material moves down a slope along a relatively planar or flat surface. Unlike rotational landslides, translational landslides typically involve less rotation of the sliding mass.

Figure C illustrates a block slide, a type of translational landslide where the moving mass consists of a large, intact block of rock or soil that slides down along a surface of rupture.

Figure D displays a rockfall, where rock fragments break off from a steep or vertical cliff and fall freely or bounce down the slope. Rockfalls are common in mountainous regions and can be triggered by weathering, earthquakes, or other factors.

Figure E portrays a topple, a type of mass movement where a rock or earth mass tilts forward and falls due to the gravitational pull, often occurring on slopes where the base of the mass is weaker or eroded.

Figure F shows a debris flow, which involves the rapid downslope movement of loose soil, rocks, and organic material mixed with water. Debris flows are highly fluid and can travel long distances, often following river valleys.

Figure G depicts a debris avalanche, a fast-moving, turbulent flow of debris that can travel at high speeds, carrying large volumes of material downslope. Debris avalanches are typically triggered by earthquakes, volcanic activity, or heavy rainfall.

Figure H represents an earthflow, where fine-grained materials, such as clay or silt, flow downslope in a viscous manner. Earthflows typically move slowly and are common in humid environments.

Figure I illustrates creep, a slow and gradual downslope movement of soil or rock, often imperceptible over short time periods. Creep is usually indicated by curved tree trunks or tilting fences and other structures on the slope.

Figure J at the bottom of the image shows a lateral spread, which occurs when a layer of soil or rock spreads laterally due to liquefaction or the failure of underlying layers. Lateral spreads are commonly associated with earthquakes and can cause significant ground deformation.

This image provides a comprehensive overview of the different types of landslides and mass movements, each characterized by distinct movement mechanisms and material compositions.

Figure 9.7.2 Ferguson Rockslide

The image shows an aerial view of a steep, rocky hillside with a distinct slope and exposed rock formation. The terrain is densely vegetated with green shrubs and trees on both sides, highlighting the rugged and natural landscape. At the base of the slope, a river flows, bordered by additional vegetation, indicating a typical riverine environment.

The rock formation appears to be a result of geological processes, with visible layers and a clear demarcation between the rocky slope and the surrounding vegetation. The slope seems to have experienced some erosion, evidenced by the debris and exposed rock at its base.

This landscape exemplifies the natural beauty and geological diversity of the region, providing insight into the area's geomorphological history and the ongoing natural processes shaping it.

Figure 9.7.3 3D Model of Rock Shed Used to Mitigate Mass Wasting Effects in Merced River Canyon

The image shows a digitally rendered model of a slope stabilization and road protection structure. A steep hillside, covered in a combination of greenery and exposed rock, looms in the background. The slope has a grid pattern of reinforcement to prevent erosion and landslides.

In the foreground, a multi-arched concrete structure runs parallel to the base of the hillside. This structure likely serves as a protective barrier for the roadway running adjacent to it, shielding it from potential rockfalls and debris. The road, which is well-paved and marked with yellow lines, is seen to the left of the protective barrier.

The barrier design includes a series of evenly spaced arches, providing structural integrity and potentially allowing for drainage and maintenance access. The overall scene reflects engineering efforts to ensure road safety in areas prone to natural hazards such as rockfalls and landslides, highlighting the integration of civil engineering and environmental considerations.

Figure 9.7.4 Relief and fault map of the Sierra Nevada

The relief map of the Sierra Nevada region illustrates the diverse topography and significant geological features, including various fault lines that shape the landscape. Elevation is color-coded, with green indicating lower elevations and brown to white representing higher elevations. The map highlights several major faults, including the Fort Sage Fault, Kern Front Fault, Hilton Creek Fault, Kern Canyon Fault, Owens Valley Fault, Southern Sierra Nevada Fault, Garlock Fault, White Wolf Fault, and Little Lake Fault. These faults are marked prominently with black lines, indicating their locations and extents.

The map also shows key geographical features and cities such as San Francisco, San Jose, Sacramento, and Fresno, providing a reference for the location of these faults within the broader context of California's geography. Additionally, the elevation scale provided on the map gives a clear understanding of the varying altitudes across the Sierra Nevada region, from the low-lying valleys to the high mountain peaks. This detailed depiction aids in comprehending the complex interplay between tectonic activity and topography in the Sierra Nevada, offering insights into the region's geological history and ongoing processes.

The image is a detailed map of Lake Tahoe, highlighting the McKinney Bay landslide area and various notable locations around the lake. The map is overlaid on a satellite image and includes contour lines and other geological features.

The main map shows Lake Tahoe's bathymetry and the surrounding topography, with color-coded contours indicating elevation changes. The lake's shoreline is marked with a red line, while the landslide area is delineated by a dashed white line labeled "McKinney Bay Landslide." A black dashed line runs vertically through the center of the lake, marking the state boundary between California (CA) on the left and Nevada (NV) on the right.

Various bays and points around the lake are labeled, including Agate Bay, Crystal Bay, Incline, Secret Harbor, Skunk Harbor, Glenbrook, Logan Shoals, Cave Rock, Zephyr Cove, Stateline, Tahoe Keys, Baldwin Beach, Emerald Bay, Rubicon Point, Lonely Gulch, Meeks Bay, and Tahoe City Shelf. The map also identifies underwater features and depositional areas with shaded regions and labeled annotations.

In the upper left corner, there is an inset map showing a simplified outline of Lake Tahoe with the location of the McKinney Bay landslide. Another inset in the lower left corner provides a broader regional context, showing the lake's position relative to California and Nevada.

This map provides a comprehensive view of the geological features and significant locations around Lake Tahoe, emphasizing the impact and extent of the McKinney Bay landslide.