The hills rise up to about 300 feet (100 m). Estimated volume of the deposits is 10 cubic miles (45 cubic km). These deposits cover an area of 260 square miles (675 square km) in the Shasta Valley and occur over 45 miles (70 km) from the volcano. The hummocks in the foreground are debris avalanche deposits from Shasta that are between 300,000 and 380,000 years old. Shastina is made up of mostly andesite flows and several dacite summit domes. Shastina (12,330 feet, 3,759 m) from high on Shasta.
This pyroclastic flow covers the ground now occupied by the town of Weed. Diller Canyon, the prominent canyon on Shastina, funneled a large pyroclastic flow about 9,230 years ago. Hotlum cone was active only a few centuries ago. The Hotlum cone is the youngest eruptive center and forms Shasta's summit and the north and northeast flanks. Shastina, the prominent cone on the west flank of Shasta, was active around 9,200 years ago. Misery Hill, on the northwest flank of the Sargeants Ridge cone, was active between 15,000 and 20,000 years ago.
The oldest center is the Sargeants Ridge cone, located on the strongly eroded lower slopes of Shasta, was active about 450,000 years ago. The volcano is composed of four overlapping andesiteeruptive centers all visible in the photograph. Shasta, 40 miles (65 km) south of the California-Oregon border is the second highest (14,161 feet, 4,317 m)mountain in the Cascade Range.
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