What You Can See From Here Today

North and South Table Mountains are remnants of ancient lava flows now separated and eroded by Clear Creek. The Dakota Hogbacks on both sides were once continuous, but the Golden Fault cut them off, and the rocks at this location were uplifted along that fault to stand two miles higher than the same rocks beneath the Table Mountains. A geologic cross-section of Lookout Mountain, the City of Golden, and the Table Mountains shows that the rocks here on the left side of the diagram are igneous and metamorphic rocks more than 1.7 billion years old. As these ancient rocks were uplifted, originally flat sedimentary rocks were faulted and tilted, with some tilted to near vertical. Those sedimentary rocks eroded more easily to form the valley, while the more resistant igneous and metamorphic rocks formed the mountains. Igneous rocks formed by crystallizing from a melt and include granite in the mountains to the west and the Table Mountain lava flows; metamorphic rocks formed without melting through heat and pressure acting on preexisting rocks and include the rock around the museum and grave site; sedimentary rocks formed at the earth’s surface through weathering, erosion, and deposition and include rocks beneath Golden and along the mountain front, though well-cemented sandstone and conglomerates such as the Dakota Hogbacks are more resistant. About 10,000 feet of movement has occurred along the Golden Fault. The Laramide mountain-building episode began 68 million years ago and continued for about 25 million years, uplifting the Colorado Rocky Mountains.

Colorado · United States