Raplee Monocline

Raplee Ridge and Mexican Hat Rock

Raplee Ridge is a quite short monocline (8+ miles, 14 kilometers, in length) compared with its three neighbors - Comb Ridge, across the San Juan, with a length of 120 miles, Waterpocket Fold, northwest across Lake Powell, at 100 miles in length, and the Cockscomb segment of the East Kaibab Monocline to the west, on the other side Lake Powell, that is 149 miles long.

Raplee Ridge lies just across the San Juan River from Mexican Hat, Utah (census-designated place, 2010 pop 31), which gets its name from Mexican Hat Rock, which sits in front of Raplee Ridge - the banner photo.

Our photos do not do Raplee Ridge justice - in bright sunlight the interleaved layers of gray gypsum or salt and red sedimentary rock present a truly beautiful sight, which does not show up very well at all in these photos.

Geologists propose that Raplee Ridge and its neighbors were formed by the same tectonic plate subduction that formed the Rocky Mountains during the Laramide orogeny 80 to 70 million years ago (some geologists say 70 to 50).  We have always referred to it as the Raplee Ridge monocline, but there seems to be some controversy about it being a monocline (some geologists) or an anticline (other geologists, USGS, National Geographic).  The Google Earth satellite image tends to support either argument.  So, for the time being, we will simply call it Raplee Ridge.

The San Juan River runs through gorges and canyons on its course through Utah, past Bluff (the name tells all), cuts through Comb Ridge, through The Narrows as San Juan Canyon cuts through Raplee Ridge, crosses US163 at Mexican Hat, zigzaggs through Goosenecks State Park, and through more incised canyons until it reaches the Coloardo at Lake Powell in the Glen Canyon National Recreation Area.  Commercial expeditions down the river, from one to seven days, explore the magesty, beauty, geology, and archaeology of the San Juan canyons between Bluff, Utah, and Lake Powell.

Menu selections include a Google satellite image of the four area monoclines including Raplee Ridge (hardly visible on that image), and a link to the Wikipedia article on the Laramide orogeny.