A Geological Tour of Denver, Golden, and Colorado's Front Range

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The Golden Table Tops

Golden Table Tops

North Table Mountain - The east face of North Table Mountain as seen from South Table Mountain. Ralston Dike, the source of the magma flow, is hidden behind North Table Mountain.

North and South Table Mountain

A lake of lava...

From Ralston Dike, three miles north of Golden, to Green Mountain, south of the city, is a distance of about ten miles. Lava, emerging from a vent at Ralston Dike, flowed southeast as far as Green Mountain, to form, for a time, a ten-mile long lake of liquid lava.  Just when this occurred has been debated.  A Tyrannosaurus Rex tooth found on South Table Mountain in 1874 (and identified in 2003), suggests that the lava flow occurred at least 65 million years ago, before dinosaurs became extinct. Comparison of the remains of the lava flow with nearby formations has led others to conclude that it took place much later, possibly around 35 million years ago.  Adding to confusion over the date is confusion over the source of the flows. Some believe that the lava on North Table Mountain originated in Ralston Dike. Others have speculated that it came from a lava vent or vents on North Table Mountain itself (the Zeise Peaks). In addition, three separate lava flows have been identified.  Two capping flows cover the original.  The ten-mile flow which evidence suggests originated in Ralston Dike, was not the earliest of the lavas, but the second, (the first of the two capping flows).  The capping flows are composed of  shoshonite, a potassium-rich basalt.[1]

If the Ralston Dike lava cooled as one large mass, large portions were eliminated by erosion.  Four separate structures are all that remain of the original formation: Ralston Dike, North Table Mountain, South Table Mountain, and part of the north and northeast slopes of Green Mountain.  (Most of Green Mountain is made of conglomerate from eroding mountain peaks to the north and west, not the basalt flowing from Ralston Dike.) Predecessor streams of Clear Creek cut a large channel through the main formation at Golden, splitting it into North and South Table Mountain.

North Table Mountain is roughly two miles long by one mile wide, while South Table Mountain is about two and a half miles long with an average width of three-quarters of a mile.  At its base, North Table Mountain covers 2,130 acres. The plateau on top covers about 1,000 acres, half the acreage of the base.  The highest point is North Zeise Peak, with an elevation of 6566 feet.[2]


(1) J. Harlan Johnson, "The Geology of the Golden Area, Colorado," Quarterly of the Colorado School of Mines, Vol 25, No. 3 (Golden, CO 1930), pp. 20-21;
W. A. Waldschmidt, "The Table Mountain Lavas and Associated Igneous Rocks Near Golden, Colorado," 34 Colorado School of Mines Quarterly, (Golden, CO 1939), pp. 24-25;
Martin Lockley, "Fossil Footprints of the Dinosaur Ridge and Fossil Trace Areas, 2nd ed." Friends of Dinosaur Ridge and the University of Colorado at Denver Tracker Research Group, (Golden, CO 2003), p. 54;
Paul D. Kilburn and Sally L. White, "North Table Mountain: Its History and Natural Features," Jefferson County Nature Association, (Morrison, CO 1992), p. 3;
Harald Drewes and John Townrow, "Trailwalker's Guide to the Dinosaur Ridge, Red Rocks and Green Mountain Area, 2nd Edition" Friends of Dinosaur Ridge, (Morrison, CO 2005), p. 31.
(2) Waldschmidt, "The Table Mountain Lavas," pp. 8-9;
Kilburn and White, "North Table Mountain," p. 3.