Molten lava roils and bubbles deep inside our planet.
Surging upward into the cracks and crevices throughout the lowest levels of the earth’s crust, pools of slowly cooling magma form and settle before reaching the surface.
When cooled, they create a large body of igneous rock. Comprised of coarse-grained granite, when these plutons are 40 square miles (100 square kilometers) or more, they become a batholith.
The word batholith comes from the Greek word bath and the suffix -lith, which means deep rock. It’s the perfect name for these subterranean monoliths.
How They’re Formed
The majority of these massive rocks form deep inside mountain folds that have endured faulting. These cracks and crevices create the perfect places for the magma that becomes a batholith to slip in and form new structures once it cools.
Batholiths are never made up of a single structure — they’re too huge. These colossal formations are made up of multiple plutons blended into a dome shape that remains hidden beneath the surface of the planet. Over time, the erosion of that overlaying layer exposes the batholith for all to see.
Once it’s exposed, the difference in pressure and the influence of weather removes layers with rough edges and sharp corners. The resulting rock surface is clean and rounded. This uniquely shaped structure is visible for miles.
Size & Depth
Batholiths are a minimum of 40 square miles in size. Beyond that, their size, depth and shape vary greatly depending on the factors that influenced them during their creation and emergence. Some remain smooth and rounded for years to come, others become jagged peaks. Some of these extend more than 1,000 miles.
While it was once believed that these intrusive igneous rock structures extended to unknown depths, studies conducted around 2013 proved that this may not be true. Many of these studies indicated that batholiths could be no more than 6 to 9 miles (10 to 15 km) deep.
The Significance of Batholith to Geology and Humanity
According to the United States Geological Survey conducted by the Department of the Interior, the study of batholiths is important for understanding the ecology and mineral resources of the area as well as the inherent natural hazards. For the first two areas, the feldspar and quartz composition that is nearly always present in batholiths is a treasure trove for research. Studying the damage done by the significant internal stress batholiths are subjected to can help areas prepare for earthquakes and landslides.
Sierra Nevada Range
The most well-known batholith is at the core of the Sierra Nevada mountain range. It was exposed as the mountains rose eroding the material that had covered the monstrosity for millions of years. The exposed peaks of this batholith became the jagged granite peaks of High Sierra.
The Sierra Nevada range is the largest mountain range in the contiguous United States. Furthermore, the Sierra Nevada summit Mount Whitney is the tallest peak. Other mountains within the Sierra Nevadas that are part of the batholith include Half Dome and El Capitan in Yosemite National Park.
Yosemite National Park
In 1890, Yosemite National Park was established covering nearly 1,200 square miles, including portions of the Sierra Nevada range. El Capitan and Half Dome are part of that section. Today, thousands of people from all over the world visit Yosemite. During those visits, people traverse areas of the Sierra Nevada batholith containing rocks that could be more than 450 million years old.
California Gold Rush
The Sierra Nevada mountains witnessed the dawning of the California Gold Rush as hopeful miners with dreams of striking it rich rushed to its mineral-rich foothills in the early middle of the 19th century. The rush began in January of 1848 when the first gold flakes were found in American River at the base of the Sierra Nevada Mountains near Coloma, California. Soon, communities in the area were inundated by more than 4,000 of these miners. This changed the communities and California forever.
Batholiths Around the World
In addition to the Sierra Nevada range, there are lesser-known batholiths around the world. These outcroppings range in size and age with many of them containing peaks and summits that are better known than the batholith itself. In fact, most people don’t even know that the batholith exists. Regardless, the world’s batholiths include:
- Egypt: Aswan Granite batholith
- Ghana: Cape Coast batholith
- South Africa: Darling batholith
- Uganda: Mubende batholith
- Antarctica: Antarctic Peninsula and Queen Maud batholiths
- Siberia: Angara-Vitim batholith
- India: Bhongir Fort batholith and Mount Abu
- Himalaya: Gangdese, Karakorum and Trans-Himalayan batholiths
- Kazakhstan: Kalba-Narym batholith
- Thailand: Tak batholith
- Central Asia: Tien Shan batholith
- England: Cornubian and North Pennine batholiths
- Ireland: Donegal and Leinster Boulder batholith
- France: Mancellian batholith
- Norway: Sunnhordaland and Bindal batholiths
- Australia: Cullen, Kosciuszko, Moruya and New England batholiths
- New Zealand: Median batholith
- Argentina: Achala and Cerro Aspero batholiths
- Peru: Coastal and Cordillera Blanca batholiths
This continent has a number of batholiths, which is likely due to a large number of tectonic plates that surround North America. Scientists believe these plates play a large part in not only the formation of batholiths but their emergence as well. North American batholiths include:
- Bald Rock batholith
- British Virgin Islands
- Chambers-Strathy batholith
- Boulder batholith
- Town Mountain Granite batholith
- Golden Horn batholith
- Idaho batholith
- Ruby Mountains
- Stone Mountain
- Wyoming batholith
- Pike’s Peak Granite batholith
- Kenosha batholith
- Rio Verde batholith
Batholiths shape and reshape the landscapes of the world. These enormous intrusive rocks create some of the most beautiful vistas in nature. Like the Sierra Nevada range, they have a long history that changed the course of the people who live around them.