Category: Geology

Transverse Ranges

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The Transverse Ranges are a group of mountain ranges in Southern California, USA. They run east-west and are characterized by their unique orientation, perpendicular to the typical north-south alignment of most other mountain ranges in North America. The Transverse Ranges play a significant role in the geography and climate of Southern California.

San Gabriel Range
San Bernardino Range

The main Transverse Ranges include:

  1. San Gabriel Mountains: Located northeast of Los Angeles, the San Gabriel Mountains are a prominent part of the Transverse Ranges. They contain several peaks over 10,000 feet, including Mount San Antonio (Mt. Baldy), the highest peak in the range.
  2. San Bernardino Mountains: To the east of the San Gabriel Mountains, the San Bernardino Mountains are another subrange within the Transverse Ranges. They include prominent peaks such as San Gorgonio Mountain, the highest peak in Southern California.

Additional Transverse Ranges (not in project)

  1. Santa Ynez Mountains: Situated to the northwest of Los Angeles, the Santa Ynez Mountains are part of the Transverse Ranges and run parallel to the coast. They contribute to the scenic backdrop of the Santa Barbara area.
  2. Santa Susana Mountains: Located northwest of Los Angeles, the Santa Susana Mountains are a smaller subrange within the Transverse Ranges.
  3. Topatopa Mountains: Situated north of Ventura, the Topatopa Mountains are part of the Transverse Ranges and are known for their distinctive east-west orientation.

Rain Shadow Desert

The Transverse Ranges have a significant impact on the climate of Southern California. They act as a barrier to moist air coming from the Pacific Ocean, causing a rain shadow effect. This results in a drier climate on the leeward (eastern) side of the ranges, contributing to the arid conditions of the inland areas.

Earthquakes

San Juan Capistrano (Wrightwood) 

December 8, 1812 | M7.5

This midmorning earthquake occurred on December 8, 1812, with an estimated magnitude of 7.5 (Mw). The location is uncertain but probably on the San Andreas fault near Wrightwood in San Bernardino County.

This quake is remembered, and named after, its death toll: forty Native Americans attending mass at San Juan Capistrano were killed when the church collapsed due to the mortar in the walls failing. Records from this time are poor, but it is likely that there was also damage at Mission San Gabriel and in San Diego.

1857 Fort Tejon Earthquake

The Fort Tejon earthquake occurred on January 9, 1857, and is one of the largest historical earthquakes in California. It had an estimated magnitude of 7.9 and was associated with the southern segment of the San Andreas Fault

1952 Kern County Earthquake

The 1952 Kern County earthquake occurred in southern California on July 21, 1952. This earthquake had an estimated magnitude of 7.3, making it one of the most powerful earthquakes in California’s history. The epicenter was near the White Wolf Fault in the southern Sierra Nevada mountain range.

1872 Owens Valley Earthquake

The 1872 Owens Valley earthquake was a significant seismic event on March 26, 1872, in Owens Valley, California, USA. The earthquake is estimated to have had a magnitude of 7.4 to 7.9, making it one of the largest historical earthquakes in California.

Cajon Pass 

July 22, 1899 | M5.7

On July 22, 1899, a magnitude 5.7 (ML) earthquake occurred about 15 miles northwest of San Bernardino. People reported feeling this quake in much of Southern California. No deaths were reported, but the number of injuries is uncertain.

The earthquake caused landslides that blocked the Lytle Creek Canyon road and the road through Cajon Pass. It also caused some damage to buildings in San Bernardino, Highland and Patton. Minor damage was also reported in Redlands, Pomona, Riverside, Pasadena and Los Angeles.

Manix

April 10, 1947 | M6.5

On April 10, 1947, a magnitude 6.5 (Mw) earthquake occurred about 25 miles east of Barstow. Because of its remote location, it didn’t cause a lot of damage. However, there were reports of cracked floors and walls, a few collapsed structures, and heavy objects being moved.

This quake was notable because it was the largest earthquake at that time—and the first to cause surface rupture (about three miles of rupture)—in the Mojave Block tectonic region.

Big Bear Earthquake

TYPE OF FAULTING: left-lateral strike-slip
TIME: June 28, 1992 / 8:05:30 am PDT
LOCATION: 34° 12′ N, 116° 49.6′ W 8 km (5 miles) SE of Big Bear Lake 40 km (25 miles) east of San Bernardino
MAGNITUDE: MSS.4

DEPTH: 5 km

While technically an “aftershock” of the Landers earthquake (indeed, the largest aftershock), the Big Bear earthquake occurred over 40 km west of the Landers rupture, on a fault with a different orientation and sense of slip than those involved in the main shock — an orientation and slip which could be considered “conjugate” to the faults which slipped in the Landers rupture.

The Big Bear earthquake rupture did not break the surface; in fact, no surface trace of a fault with the proper orientation has been found in the area. However, the earthquake produced its own set of aftershocks, and from these, we know the fault geometry — left-lateral slip on a northeast-trending fault.

Following the Landers mainshock by three hours (it occurred while TV news coverage of the Landers earthquake was being broadcast live from Caltech), the Big Bear earthquake caused a substantial amount of damage in the Big Bear area, but fortunately claimed no lives. Landslides triggered by the jolt blocked roads in the San Bernardino Mountains, however, aggravating the clean-up and rebuilding process.

1952 Kern County Earthquake

The 1952 Kern County earthquake occurred on July 21, 1952, in southern California. This earthquake had an estimated magnitude of 7.3, making it one of the most powerful earthquakes in California’s history. The epicenter was near the White Wolf Fault in the southern Sierra Nevada mountain range.

Key points about the 1952 Kern County earthquake:

  1. Magnitude and Intensity: The earthquake was 7.3 and is considered a major event. It caused strong shaking in the affected areas.
  2. Location: The epicenter was near Arvin in Kern County, California.
  3. Damage: The earthquake caused significant damage in several communities, including Bakersfield, Tehachapi, and Arvin. Many buildings were damaged, and some were destroyed. Infrastructure, such as roads and bridges, also suffered.
  4. Casualties: The earthquake resulted in 12 fatalities and numerous injuries. The loss of life and property damage were considerable.
  5. Aftershocks: Like many major earthquakes, the 1952 Kern County earthquake was followed by a series of aftershocks, some of which were strong enough to cause additional damage.
  6. Effects on Oil Fields: The earthquake had notable effects on oil fields in the region. The shaking caused ground rupture and surface faulting, impacting oil extraction operations.
  7. Response and Study: The earthquake prompted increased interest and research in engineering and seismology. Lessons learned from the event contributed to advancements in earthquake-resistant building design and seismic hazard assessment.

The 1952 Kern County earthquake was a significant event in the history of seismic activity in California, and it played a role in shaping earthquake preparedness and research efforts in the region.

1872 Owens Valley Earthquake

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The 1872 Owens Valley earthquake was a significant seismic event on March 26, 1872, in Owens Valley, California, USA. The earthquake is estimated to have had a magnitude of 7.4 to 7.9, making it one of the largest historical earthquakes in California.

Some key points about the 1872 Owens Valley earthquake:

  1. Location: The earthquake’s epicenter was near Lone Pine in Owens Valley, in eastern California, near the eastern Sierra Nevada mountain range.
  2. Effects: The earthquake caused extensive damage in the Owens Valley region. The town of Lone Pine suffered the most severe damage, with many buildings collapsing. In addition to the structural damage, the earthquake triggered ground ruptures, creating surface faulting along the eastern Sierra Nevada.
  3. Surface Rupture: The earthquake is notable for the significant surface rupture that occurred along the Owens Valley fault. This rupture extended for about 30 miles (48 kilometers) and displaced the ground horizontally by as much as 15 feet (4.5 meters). This surface rupture remains visible today as a scar on the landscape.
  4. Aftershocks: Numerous aftershocks followed the mainshock, continuing for several months. These aftershocks contributed to ongoing damage and hampered recovery efforts.
  5. Impact on the Landscape: The earthquake caused changes to the landscape, including the formation of new fault scarps and the uplifting of land along the eastern Sierra Nevada. These changes are still studied by geologists today.
  6. Historical Significance: The 1872 Owens Valley earthquake is historically significant in the study of seismic activity in California. It provided valuable data for understanding the behavior of faults and the effects of large earthquakes on the landscape.

It’s worth noting that the Owens Valley region remains seismically active, and scientists continue studying the area to understand future earthquakes’ potential better. The 1872 event serves as a reminder of the seismic hazards associated with the complex fault systems in California.

Lone Pine

Owens Valley

Eastern Sierra Nevada

Mormon Rocks

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The Mormon Rocks, also known as the Rock Candy Mountains, are a series of distinctive sandstone outcrops in the Cajon Pass, a mountain pass in the San Bernardino Mountains of Southern California. The Cajon Pass is a critical transportation corridor connecting the Los Angeles Basin with the Mojave Desert and beyond.

Here are some key points about Mormon Rocks and their significance:

  1. Location: The Mormon Rocks are within the Cajon Pass, traversed by Interstate 15 and several major railroad lines. The rocks are easily visible from the highway, making them a notable geological feature.
  2. Geological Formation: The rocks are sedimentary sandstone and formed through tectonic and erosional processes over millions of years. The distinctive red and white banded appearance is due to iron oxide (hematite) and other minerals.
  3. Cultural Significance: The Mormon Rocks have cultural and historical significance. The area is named after a group of Mormon pioneers who passed through the Cajon Pass in the mid-19th century during their westward migration. The rocks are a prominent landmark in the pass and have been featured in various forms of media.
  4. Recreational Opportunities: The area around Mormon Rocks provides outdoor activities and recreation opportunities. There are trails and viewpoints where visitors can appreciate the geological formations and enjoy scenic views of the surrounding landscape.
  5. Conservation: The Mormon Rocks are part of the San Bernardino National Forest, and efforts are made to preserve and protect the natural and cultural resources in the area.
  6. Railroad Transportation: The Cajon Pass is a crucial route for road and rail traffic. The presence of the rocks adds to the landscape’s visual appeal and has made the pass a notable location for train enthusiasts who enjoy watching trains navigate the steep grades of the pass.

Whether you are interested in geology, history, or simply enjoying scenic landscapes, the Mormon Rocks in the Cajon Pass offer a unique and visually striking destination. If you plan to visit, be sure to follow any posted regulations and respect the natural environment.

Desert Rockhounding

Desert rockhounding is a popular recreational activity that involves searching for, collecting, and identifying rocks, minerals, gemstones, and fossils in arid regions. Deserts often have unique geological formations and a diverse range of minerals, making them interesting and rewarding for rockhounding enthusiasts. Here are some tips for desert rockhounding:

  1. Research the Area: Before heading out, research the desert area you plan to explore. Learn about the geology, rock formations, and the types of minerals or gemstones commonly found in that region. Geological maps and online resources can be valuable tools.
  2. Check Regulations: Be aware of any regulations or restrictions in the area you plan to visit. Some areas may have rules about collecting rocks, and respecting these regulations is important to preserve the environment.
  3. Safety First: Deserts can be challenging environments with extreme temperatures. Wear appropriate clothing, including a hat, sunscreen, and sturdy footwear. Carry plenty of water and be mindful of your surroundings to ensure a safe and enjoyable rockhounding experience.
  4. Use the Right Tools: Bring the necessary rock-hounding tools, such as rock hammers, chisels, safety glasses, gloves, and a backpack to carry your finds. A field guide to rocks and minerals can help you identify your discoveries.
  5. Explore Washes and Dry Creek Beds: Water action in desert washes can concentrate rocks and minerals, making these areas fruitful for rockhounding. Explore dry creek beds, washes, and areas where water has flowed in the past.
  6. Look for Indicator Minerals: Certain minerals may indicate the presence of valuable gemstones or other interesting specimens. Learn to recognize indicator minerals and follow their trail to potential collecting sites.
  7. Be Respectful: Leave no trace and practice ethical rockhounding. Avoid damaging plants, disturb the environment as little as possible, and fill in any holes you may dig. Remember that some areas may be protected, and it’s important to respect these conservation efforts.
  8. Join Rockhounding Clubs: Consider joining local rockhounding clubs or groups. These organizations often have experienced members who can share knowledge about the best collecting sites and provide guidance on responsible rockhounding practices.
  9. Time Your Visit: The best time for desert rockhounding is during the cooler months, as summer temperatures can be extremely high. Early morning and late afternoon are generally more comfortable and offer better lighting for observing and collecting.
  10. Learn to Identify Rocks: Familiarize yourself with the characteristics of rocks and minerals commonly found in the desert. Understanding the properties, colors, and formations of different specimens will enhance your rockhounding experience.

Always be aware of your impact on the environment and prioritize conservation while enjoying the excitement of discovering rocks and minerals in the desert.

Rockhound

Fort Tejon Earthquake 1857

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The Fort Tejon earthquake occurred on January 9, 1857, and is one of the largest historical earthquakes in California. It had an estimated magnitude of 7.9 and was associated with the southern segment of the San Andreas Fault. Here are some key details about the Fort Tejon earthquake:

  1. Date and Time:
    • The earthquake struck on January 9, 1857.
  2. Location:
    • The epicenter was near Fort Tejon in Kern County, California.
  3. Magnitude:
    • The earthquake is estimated to have had a magnitude of 7.9.
  4. San Andreas Fault:
    • The earthquake was associated with the southern segment of the San Andreas Fault.
  5. Damage:
    • The region affected by the earthquake was sparsely populated, which helped reduce casualties.
    • Significant damage occurred to buildings, infrastructure, and landscapes.
    • The earthquake caused surface rupture along the fault, creating a noticeable surface offset.
  6. Aftershocks:
    • A series of aftershocks followed the main event, further contributing to the seismic activity in the region.
  7. Impact on Landscape:
    • The earthquake caused visible changes in the landscape, with the ground surface breaking along the fault line.
  8. Historical Significance:
    • The Fort Tejon earthquake is significant in understanding the seismic history of California.
    • It provided valuable information about the behavior of the San Andreas Fault and the potential for large earthquakes in the region.

It’s worth noting that the Fort Tejon earthquake occurred when the population in the affected area was relatively low, which helped mitigate the impact on human lives. The earthquake remains an important event in studying California’s seismic activity and understanding earthquake hazards in the region.

Geology of the Eastern Sierra Nevada

Introduction:

The Eastern Sierra Nevada boasts a rich geological history that spans millions of years. This region offers a captivating glimpse into Earth’s past, from towering granite peaks to ancient volcanic formations. The fascinating geology of the Eastern Sierra Nevada and its unique features make it a geologist’s paradise.

Formation of the Sierra Nevada Range:

The Sierra Nevada Range, including the Eastern Sierra Nevada, began forming around 100 million years ago during the Mesozoic Era. It was the result of tectonic plate movements, specifically the subduction of the Pacific Plate beneath the North American Plate. This process resulted in the uplifting and folding of the Earth’s crust, giving rise to the majestic mountain range we see today.

Granite and Glaciers:

One of the defining features of the Eastern Sierra Nevada is its abundance of granite. The region is home to the largest exposed granite batholith in the world, aptly named the Sierra Nevada Batholith. This enormous body of intrusive igneous rock formed deep beneath the Earth’s surface and was gradually exposed through erosion over millions of years.

During the last Ice Age, glaciers sculpted the Eastern Sierra Nevada, leaving behind stunning landscapes. Glacial activity carved out U-shaped valleys, polished granite surfaces and created glacial lakes such as Mono Lake and Convict Lake. These remnants of the Ice Age are a testament to the dynamic forces that shaped the region.

Volcanic Activity:

Eastern Sierra Nevada is also home to a number of volcanic features. The Long Valley Caldera, located just east of the Sierra Nevada Range, is a prime example of volcanic activity in the region. This massive volcanic depression formed around 760,000 years ago during a cataclysmic eruption that released an estimated 600 cubic kilometers of magma.

Within the caldera lies the famous Mono-Inyo Craters, a chain of volcanic domes and craters. These volcanic formations offer a glimpse into the region’s volcanic history and provide evidence of past eruptions that have shaped the landscape.

Mineral Deposits:

The Eastern Sierra Nevada is known for its rich mineral deposits. Gold, silver, and copper have been mined in the region since the mid-1800s, attracting prospectors during the California Gold Rush. The Bodie State Historic Park, a well-preserved ghost town, stands as a reminder of the mining boom that once thrived in the area.

Conclusion:

Exploring the geology of Eastern Sierra Nevada is a journey through time, where the forces of nature have sculpted a remarkable landscape. This region offers a glimpse into the Earth’s fascinating geological history, from the towering granite peaks to the remnants of ancient volcanoes. Whether you are a geology enthusiast or simply appreciate the beauty of nature, Eastern Sierra Nevada is a destination that will leave you in awe of the Earth’s geological wonders.

(c) Walter Feller

Geology of the Lower Colorado River

Introduction:

The Lower Colorado River is a mesmerizing natural wonder that winds through the Southwestern United States, attracting millions of visitors annually. Beyond its scenic beauty and recreational opportunities, the geology of the Lower Colorado River offers a fascinating glimpse into the Earth’s history.

Formation of the Lower Colorado River:

The formation of the Lower Colorado River can be traced back millions of years. It all began with the uplift of the Colorado Plateau, a vast region spanning parts of Arizona, Utah, Colorado, and New Mexico. Over time, the relentless forces of erosion, primarily by the Colorado River, carved through sedimentary rock layers, exposing unique geological formations.

Canyons and Gorges:

One of the most striking features along the Lower Colorado River is the presence of deep canyons and gorges. The river has carved its way through layers of sedimentary rocks, primarily sandstones, and shales, creating stunning landscapes such as the Grand Canyon and the Black Canyon of the Colorado. These canyons offer a glimpse into the Earth’s history, with each layer representing a different period of deposition.

Rock Formations:

The Lower Colorado River area is renowned for its diverse rock formations. The region showcases various sedimentary rocks, including sandstone, limestone, and shale. These rocks provide clues about ancient environments and the processes that shaped them. Fossilized remains of plants and animals can also be found within these rock formations, offering insights into past ecosystems.

Geological Time Scale:

To truly appreciate the geology of the Lower Colorado River, it is essential to understand the concept of geological time. The river has been actively shaping the landscape for millions of years, leaving behind a rich tapestry of rocks and formations. By studying the various layers, geologists can piece together the history of the region, including ancient climates, sea levels, and tectonic events.

Conclusion:

The geology of the Lower Colorado River is a captivating subject that offers a glimpse into the Earth’s past. From towering canyons to diverse rock formations, this region tells a story of millions of years of geological processes. Exploring the Lower Colorado River is a visual delight and an opportunity to unravel the mysteries of our planet’s ancient history. So, the next time you find yourself near the Lower Colorado River, take a moment to appreciate the remarkable geology that surrounds you.

(c) Walter Feller

Geology of Death Valley

Introduction:

View of Death Valley from Chloride Cliff

Death Valley National Park is known for its extreme temperatures, vast desert landscapes, and unique geological features. Located in Eastern California, this national park is a treasure trove for geology enthusiasts.

Formation and Tectonic Activity:

Death Valley’s geological history dates back millions of years. The valley is part of the larger Basin and Range Province, characterized by its numerous mountain ranges and elongated valleys. The formation of Death Valley can be attributed to the complex interplay of tectonic forces.

Faults and Uplift:

One of the key geological features of Death Valley is the presence of faults. Numerous faults, including the prominent Death Valley Fault Zone, crisscross the region. These faults have played a significant role in shaping the landscape, creating dramatic uplifts and sinkholes.

Playa and Salt Flats:

Death Valley is home to several unique geological features, including expansive salt flats and playa. The salt flats, such as the mesmerizing Badwater Basin, are formed when water dissolves minerals from the mountains and then evaporates, leaving behind a thick crust of salt. These salt flats provide a surreal and otherworldly experience for visitors.

Mesquite Flat Sand Dunes:

The Mesquite Flat Sand Dunes offer a striking contrast to the arid landscape of Death Valley. These dunes are formed by the accumulation of wind-blown sand over thousands of years. The shifting dunes create stunning desert scenery and are a popular destination for photographers and nature enthusiasts.

Geological Time and Fossils:

Death Valley is a geological time capsule, preserving a rich fossil record that spans millions of years. Fossils of ancient marine life, plants, and animals have been discovered, providing invaluable insights into the region’s past. These fossils tell the story of a time when Death Valley was submerged under a vast inland sea.

Volcanic Features:

Volcanic activity has also left its mark on Death Valley’s geology. The park is home to several cinder cones, lava flows, and volcanic craters. Ubehebe Crater, a massive volcanic crater, is a testament to the violent eruptions that occurred in the region thousands of years ago.

Conclusion:

Death Valley National Park is a geologist’s paradise, offering a glimpse into the dynamic forces that have shaped our planet. From the towering mountain ranges to the vast salt flats and mesmerizing sand dunes, the geology of Death Valley is a testament to nature’s immense power and beauty. Exploring this unique landscape is a humbling experience that allows us to appreciate the Earth’s geological history and its ongoing processes of change and transformation.

(c)Walter Feller