Look at this–a crinoid stem. How can this be? A sea-floor fossil perched at 9000 feet in a volcanic field that stretches for miles in every direction?
Just north of Flagstaff, Mount Humphreys stands 12,633 feet above sea level, the highest summit in Arizona. Humphreys and the rest of the San Francisco Peaks are old volcanoes. Surrounding them is a necklace of dome-shaped mountains—Sugarloaf, O’Leary, Kendrick, the Dry Lake Hills, and Elden Mountain. They’re volcanic too, but they formed in a different way.
When geologists see a straight line running across a landscape, they get suspicious. Straight lines don’t happen by accident; they usually mean something. Such a line, about 155 miles long, leads north out of Grand Canyon country into Utah. It’s called the Hurricane Fault. Nineteenth-century geologist Clarence Dutton declared this one of the Earth’s most interesting “dislocations.”
The cool pine-scented air of the Kaibab Plateau at 8,000 feet is a respite on a hot day. You might want to stop at Jacob Lake Lodge for one of the best chocolate milkshakes this side of Grand Canyon. Stretch your legs, take a last slurp of that ‘shake, then pedal on down the hill on Highway 89A.
The road’s fairly level at first, but heading east it plunges downhill past yellow-belly ponderosas, through pinyon and juniper, toward sagebrush below, dropping three thousand feet in a hurry. The reason for this impressive hill--the East Kaibab Monocline.