The Geology of Table Mountain: Golden Colorado

The formation of Table Mountain and it's geologic history

Photo (c) 2007 Andrew Alden, licensed to About.com 

North and South Table Mountains are made up of igneous extrusive basaltic rock, basalt is a form of igneous rock, rocks that are formed by the process of the cooling of Earth’s magma or lava. Extrusive means that these rocks were formed on the surface as opposed to intrusive igneous rocks that are formed below the Earth’s crust. Flows of lava occurred throughout Colorado during the time of the Laramide Orogeny, a regional continental contraction of the North American Plate due  in part to the increase in elevation of the plate as a result of the  subduction of the Farallon plate under the region, this activity  can be dated back to the Tertiary period around 63 million years ago. A combination of weathering and erosion can be attributed to the process of forming the mountains, more robust basalt lava did not erode as quickly as surrounding areas,  therefore the elevation of the top of the rock now rises to more than 450 feet above the surrounding Golden Valley. Table Mountain was separated into North and South respectively by Clear Creek. The river eroded softer rock that is located beneath the harder igneous rock, causing the igneous rock to collapse, forming a small canyon between the mountains. The composition of the layers of rock (also called strata) that make up North and South Table Mountains varies depending on the geologic time frame around which that strata was formed. For example, the uppermost layer of North and South Table Mountains is comprised mostly of densely concentrated mineral crystalline structures that form an overlying layer of mafic basalt rock.  Uniquely, the North Table mountain contains an additional layer, that contains zeolites, which are made up of aluminum, silica and water, thus making it felsic, which represents the softer rock that is beneath the harder mafic rock that is more easily eroded by climatic processes.



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