California Geology: Geologic Map & History

Instructor: Fawn Goodberry

Fawn has taught as a brain training instructor with the Learning Rx. In graduate school served as a teaching assistant for Introduction to Evolution and Ecology and Population Genetics. She received her masters degree in biology in 2013.

If you have ever visited the state of California, you noticed a variety of landscapes. The ocean, the desert, and the mountains are just a few. California's terrain is very diverse and holds a rich geologic history.

Amazing Geologic Formations in California

From mountains to deserts to ocean islands and rolling hills. The state of California holds some of the world's most beautiful geologic formations. Let's look at how these unique landscapes were formed and the forces that are continuing to shape the landscape of the golden state.

This map of California shows geology and different rock types in each area.
geologic map of california

Plate tectonics, Uplift, and Mountain Formation

Much of geology has to do with plate tectonics. The outer part of the earth or the 'crust' consists of large masses called tectonic plates and many smaller plates. The location where two plates meet is known as the plate boundary. The plate boundary is where earthquakes can originate and where mountains, volcanoes, and ocean trenches are commonly formed.

As plates on the earth's surface move, they can cause several geologic processes. One of these processes is upllift, which refers to the vertical motion of a tectonic plate. This vertical motion can form mountains and other landscape features. The San Bernadino mountains were formed largely through uplift, and this force helped to raise the Sierra Nevada mountains in the Mona basin area.

While some mountain ranges are formed from uplift, there are a variety of ways mountains can be formed. Movement of tectonic plates creates volcanoes at the plate boundaries. When the volcanoes erupt, they form mountains. Volcanic Mountains include Mt. Shasta in California and Mammoth Mountain, Lassen Peak, and many other mountains in California.

Fold mountains are formed when tectonic plates run into each other, and one plate rides over the top of another plate. These are the most common types of mountains around the world. Examples include parts of the coastal range mountains in California and some areas in the Sierra Nevada.

Block Mountains are formed when tectonic plates are spreading, and the spreading creates tension causing a block in the middle of the plate to fall or the plate to split apart. Examples of mountains formed in this way include most of the Sierra Nevada and the White Mountains.

Geology Highlights of California:

While in California you have the chance to see many geologic features. Dormant volcanoes, islands that were formed by plate tectonics and remnants of inland seas. Some of the most notable examples and how they were formed are listed below.

Death Valley

Located next to the boundary of two tectonic plates, Death Valley has a long geologic history. Ancient seas were once here but filled and receded many times. Mountains were formed but eroded. Stretching of the land's surface has caused the land to decrease in elevation. Volcanic activity to the north deposited ash materials into the rock causing changes in the color of rocks in the area. Even today the landscape is ever changing.

Lake Tahoe

Known as the jewel of the Sierra, this alpine lake has the border of California and Nevada right down the middle of it. Vertical motion of tectonic plates, block faulting eruptions of the ancient mountain, and glacial retreat all helped to form this lake. The Lake is also located near 3 fault lines, The North Tahoe/ Stateline fault, the Incline Village Fault, and the West Tahoe fault. Activity and earthquakes from the faults could cause potentially dangerous size waves in the lake known as a seiche.

Lake Tahoe, located in the Sierra Nevada Mountains.
Lake Tahoe

Yosemite National Park

Some of the most famous rock formations can be found in Yosemite Valley. Half Dome and El Capitan, bring hikers and climbers from all over the world to California in hopes to reach their peaks. El Capitan stands about 3,000 feet in height and is one of the world's largest rock monoliths. Half Dome is one of the most popular and challenging hikes in California. You'll need to apply for a permit for this hike! Having to use cables to climb the final ascent to the top of the granite dome, this isn't for the faint-hearted. These two rock formations are made of almost entirely granite and were formed by glacial carving and other glacial activity around a million years ago.

Tunnel View in Yosemite National Park, showing Half Dome in the distance and El Capitan on the left.

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