The large granite building blocks of Shell Canyon are an extraordinary 2.5 billion years old. Called basement or bedrock, they form the bottom layer covering the molten material in the earth’s core. At some point, the huge plate of bedrock fractured, with one side shifting up and the other dropping down in opposite directions to form the first stage of the canyon. Stream water dramatically marks the fault line by dropping sharply over the 75 foot ledge of Shell Falls. The canyon’s colorful, coarse-grained granite formed as molten rock materials solidified. Its pink color comes from feldspar minerals, its black color from biotite, an iron-rich mica, and its white color from quartz, a hard, glassy mineral. Confined narrowly by rock and pulled strongly by gravity, water drives against the rock and moves the mountain downstream one small piece at a time, exposing millions of years of geologic history.