The 486-acre Clifty Creek Conservation Area/Natural Area is in Maries County, approximately 6 miles northeast of Dixon, past the end of Highway W. A small parking lot for the area is located alongside Maries County Road 511.
The trail head for a scenic and somewhat rugged hiking trail is at N38°01.840 W091°58.904. The trail leads from the parking lot into the adjacent Clifty Creek Natural Area. By following the trail downstream along Clifty Creek, visitors will come to the Clifty Arch natural bridge. The distance from the trailhead to the arch is 0.53 miles as the crow flies, but if the crow has to walk along the trail it's a bit more than 0.9 miles. A MO Dept of Conservation map of the area is available here.
In October 2008 the Department of Conservation completed construction on a new 2.5 mile interpretive nature trail around the area. Along the trail to the arch you'll walk through many rock formations - they're particularly striking in the winter when they're covered with icicles and frozen waterfalls. During the springtime we've noticed wild columbine growing from the crevices in the rocks. During the warm seasons, we'd recommend taking precautions against ticks and chiggers before you head down the trail!
This area, as well as much of the Ozark region, is an area of Karst geology where groundwater has dissolved the rock to form caves, sinkholes, springs, sinking creeks, seeps, and other features. In large cave systems, collapses are very common. Sometimes in large caves that are near the surface, the ceiling gets too thin and collapses. Structures such as rock domes or arches that are optimal to stand the pressure of the overlaying earth remain after the collapse. When an area collapses and erosion continues over time, the collapsed rooms are widened to create a small valley with a (former subterranean) river.
The Clifty Arch was formed when a tributary of Clifty Creek, known as Little Clifty Creek, undercut a drainage divide and was pirated by Clifty Creek. It is likely that a cave or fracture in the rock originally served as a shortcut under the rocky ridge and was later enlarged to form the natural bridge. It also appears that the same rocky ridge was once home to another natural bridge just downstream. Those that climb atop the ridge and walk in the downstream direction will notice that it ends at a steep dropoff with large boulders below. This was most likely another natural bridge that has since collapsed.
In order to claim credit for this cache, you must measure the span (side to side) and depth (front to back) of Clifty Arch by whatever means best suits your abilities. Possible methods include: using capabilities of your GPSr, measuring tape, pacing, triangulation, etc. Be advised that, in wet weather, pacing may not be an option. When you have taken your measurements, email them to the link above along with a description of how you made the measurement. Logs that are not supported with this follow-on email will be deleted.