About one-hour southwest from Williams Lake, B.C. is probably one of the most unusual, yet stunningly beautiful, areas in the entire Cariboo-Chilcotin. Here, where the Chilcotin River meanders through sandstone hoodoos and sagebrush covered hills, you will find the largest sand dune in all of British Columbia. The Farwell Canyon dune, or erg (a sand-covered desert area), nestled into a picturesque valley a short drive off Highway 20, is an easily accessible jewel of the Chilcotin region.
Molded and carved by erosion processes, the dune, sometimes referred to as the northernmost point of the Great American Desert, was formed when sandstone hoodoo formations and base rock in the nearby canyon succumbed to the relentless sculpting abilities of the wind and the water. The fine, white sand was carried up the canyon edge and swiftly deposited at the top, where the wind further manipulated it into wave-like ripples such as you might see at any beach during low-tide.
Wind is the primary architect when it comes to dune formation. There are two means by which wind is able to move individual sand grains: saltation and surface creep. Saltation accounts for about 75% of the movements by wind on sand and occurs when the wind is able to pick up grains from the surface and give them a forward momentum. However, the weight of the sand grains soon bring the grains back to the surface, where, if they encounter more sand grains, they will impact and bury, which in turn will eject a further grain downwind. It is by this process that millions of sand grains can be moved but only with a sufficient wind strength that meets the threshold to "pick" the grains up in the first place. Larger grains, incapable of being moved by weaker winds, are instead moved by "surface creep" as the numerous saltating grains slowly 'pile-drive' these larger grains downwind.
As for how the sand managed to collect at Farwell (or any other dune) in the first place, two factors are required: 1) an adequate supply of sand, and 2) winds strong enough and persistent enough to move the sand. In Farwell Canyon, the underlying sandstone geology of the area provided the supply, while the funneling action of the steep and twisting canyon walls provided the consistent wind force. Obstacles, such as a rock-outcrop or a stand of vegetation at the top of the canyon in Farwell's case, then provided the 'stopping-power' for the sand grains, causing accumulation over the eons, which slowly constructed this immense beauty.
Farwell Canyon dune itself would best be classified as a parabolic dune, one which has only a single slip-face with its 'horns' (or pointed ends of the crescent) pointed upwind. Parabolic dunes develop when vegetation begins to colonize the flanks of the dune, which stabilizes the dune, potentially retarding or stopping the movement of the dune arm edges. Eventually, the nose of the dune may be stabilized by vegetation as well, or it may continue to progress, breaking free of the arms and leaving two vegetated linear ridges in its wake.
To log this Farwell Canyon Dune Earthcache site as a visit, you must email me some scientific bit of information about the dunes such as their angle of repose. Posting a photo is not required but appreciated. But remember, sand is the killer of all cameras so take precautions - a Ziploc bag for your electronics might be a good idea to bring with you on your hike.
There is a trail to the dune almost across from the pullout near the bridge (last time I was there, a few years ago now). The hike up to the dune is a bit strenuous and may take you upwards of ½ hour but it should be well-worth it. Watch out for prickly-pear cactus on the trail, especially for our four-legged friends, should they tag along on the hunt! Wear appropriate footwear. And eye-protection from blowing sand can be very helpful. Also, be sure to check out the traditional geocaches in the area, "Chilcotin Gallery" (GCPR5G) and "Jesse's Canyon Cache" (GCN9PC). You may also get to watch the First Nations in the area fishing in the river using traditional dip-nets at the bridge next to the dunes if your visit is at the right time of year.