Discover California and Explore the Geodiversity of El Capitan in Yosemite National Park
- Wayne Munday
- Jul 20
- 3 min read
Updated: Sep 11
Sip back and discover California and explore the geodiversity of El Capitan in Yosemite National Park a spectacular wilderness of over 759,000 acres and UNESCO World Heritage Site rising from the western slope of California’s Sierra Nevada. From the Jurassic to the Cenozoic Eras around 210 - 80 million years ago the Farallon Plate a major ancient oceanic tectonic plate gradually subducted beneath the North American Plate and profoundly shaped the landscape of western North America. This subduction led to the formation of the Sierra Nevada, San Andreas Fault and Cascade Mountain Range. The subduction zone gave rise to a vast magmatic system where large coarse-grained intrusive igneous rock formations called granitic plutons slowly solidified deep within the Earth’s crust. These underground masses would eventually become the Sierra Nevada Batholith and the bedrock of Yosemite. Among Yosemite's prominent features is the El Capitan, translated as "the captain" or "the chief", a towering granite monolith rising to 2,307 meters above sea level and 1,100 meters above the western end of Yosemite Valley. More recently Alex Honnold made history in 2017 as the first person to free solo climb El Capitan. Scaling its granite face without ropes or safety gear taking only 3 hours and 56 minutes. More recently El Capitan has played its role as the visually striking backdrop to Untamed a crime thriller by Netflix starring Eric Bana as Kyle Turner, a rugged Investigative Services Branch (ISB) Special Agent with a tragic past who investigates the discovery of a woman's body under suspicious circumstance - no spoilers here!
Over the last 20 million years the once buried Sierra Nevada Batholith has been slowly uplifted as tectonic forces drove it upwards. Yosemite National Park lies within the central Sierra Nevada and is the largest fault-block mountain range in the United States of America and tilts gently westward while its eastern escarpment rises steeply due to active faulting.
As the overburden or layers of soil and rock above the Sierra Nevada Batholith were stripped away the underlying granite expanded and fractured from changes in pressure creating vertical joints and exposure to the on-going process of exfoliation or physical weathering.
Although pressure release is the main driver of exfoliation other factors such as temperature changes causing thermal expansion and contraction, freeze-thaw cycles and chemical weathering have also played a role in shaping Yosemite’s many domes, cliffs and instances of rockfall.
During the Pleistocene Epoch between 2.6 million – 12,000 years ago glacial ice advanced through the rising Sierra exploiting these fractures to scour and polish the granite bedrock by transforming once V-shaped river valleys into classic U-shaped glacial canyons such as Yosemite Valley a broad, flat-floored corridor flanked by the polished granite walls of Half Dome and El Capitan. Glacial ice not scoured the landscape it left behind moraines, striations and erratic's found today in the high country of Yosemite.
Though Yosemite’s Ice Age glaciers have long since vanished a few icy remnants remain. The Lyell and Maclure Glaciers studied by John Muir back in the 19th century are now in rapid retreat. The Lyell Glacier, in fact, no longer flows and has lost over 90% of its volume.
Yosemite National Park and especially the iconic granite monolith of El Capitan stands as a breathtaking monument to Earth’s deep-time story. Shaped by the subduction of the Farallon Plate, the rise of the Sierra Nevada Batholith and sculpted by glaciers and weathering over millions of years, this landscape is must-see wilderness destination.
