The geology of Whitmore is primarily the result of volcano eruptions. The Whitmore foothills are on the western slope of the southern end of the Cascade Range. The soil is gently sloping or rolling on broad lava flows. The dark reddish-brown surface varies from pockets of soil to very rocky surfaces, and is best used for timber, cattle grazing and apple orchards.

Erosion has worn down the original volcanos. The lava flow (olivine basalt) probably came from vents in the headwaters of Glendenning Creek, and/or possibly the two cinder cones [small volcanos] above the creek headwaters, six miles east and a little north of Whitmore. This basalt, about one million years old, is high in aluminum oxide, 18.4 percent. The area directly north of Whitmore is a narrow belt of material that was blown out of a volcano in a hot gas cloud.

On Blue Mountain in Whitmore, uplifting and faulting have exposed cretaceous age layers (some 130,000,000 years old), that have revealed ancient shells of marine life.

South Cow Creek has cut a deep canyon, exposing newer rocks that are dark gray. In some places erosion has exposed rocks that were once on the ocean floor. Cow Creek and its tributaries drain about four-hundred-twenty-six square miles.

A California Development Board report, in 1916, stated:

The Whitmore Fern section is situated in the eastern part of Shasta County, on the western slopes of the Sierra Nevadas. [Note; Mt. Lassen is now considered the southern limit of the Cascades.] It extends north to Clover Creek, south to Bear Creek; the summit of the Sierras forms its eastern boundary, the foothills its Western. The arable portion, about 1200 acres, is now under irrigation and cultivation.

This section presents a broken area of small fertile pockets in creek bottoms and arable foothills. The agricultural areas are small and scattered, the surrounding country being hilly and timbered. The elevation varies from 1800 feet to 4600 feet, being 2200 feet at Whitmore. The soil is a very uniform, red volcanic clay loam from two to 10 feet in depth, interspersed with streaks of adobe. A few pockets of silt loam are found along the lower elevations.

Mt. Shasta, fifty miles north of Whitmore, as the ashes fly

In 1862 William H. Brewer, an explorer, looked out over the area from Mt. Shasta: To the south there are mountains for about fifty miles, then the great Sacramento Valley. The latter was entirely filled with smoke and haze, the surface as level as the sea, and rising above it was the sharp Lassen’s Butte [Mt. Lassen], remarkably distinct although near a hundred miles distant. It rises like an island of black rock and white snow from this sea of fog, a grand object.

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