Rocks in Kern County consist of all three basic types. Igneous, Metamorphic, and Sedimentary. Each rock type can be interlaced with the other types.

Igneous rocks in Kern County are of both deep and surface volcanic material. In the El Paso Mountains and throughout the Mojave Desert and Great Basin Desert many of the mountains are comprised of basalt which exploded out of the earth by volcanic action.

There are few remnants of surface volcanic activity in Kern County's portion of the Sierra. North, in Tulare County, rests the inactive Golden Trout Creek Volcanic area. Along the north fork of the Kern River there is a small section of basalt that can be seen from Lloyd Meadows Road along the Rattlesnake drainage east of the Needles lookout.

The Sierra Nevada also has significant chucks of metasedimentary material that is from the ancient Sierra that rose and then eroded over the past 90-200 million years. This is frequently referred to as roof pendants. As the young Sierra rose, it pushed up the ancient remnants of the eroded Sierra. The older Sierra was mostly sedimentary rock that metamorphosed under the extreme heat and pressure of the rising chambers of granite that were extruding through the original rocks.

Most of the rock in today's Sierra Nevada is granite, which is an igneous rock that forms from magma that cools extremely slowly deep within the protective chamber of earth. The longer the cooling the larger the crystals in the granite.