Coal Vein Trail

Coal Vein Trail is an easy 0.8-mile loop through the ground reshaped by an underground coal fire. Allow 30 to 45 minutes to follow the numbered geology stops, descend into a sheltered seasonal-stream valley, and climb back past a red clinker overlook. It is a good compact walk if you want to understand how these hills formed; for bigger park views, choose a longer trail. The coal seam stopped burning in 1977, so this is a walk through its aftermath, not an active fire.

The outer circuit is 0.8 mile. A shorter 0.6-mile inner loop is also signed; this record maps the outer route. Take the numbered brochure with you, since paper copies at the trailhead sometimes run out.

Stay left at the start to follow the stops in numerical order. The path crosses open slopes, drops on stairs into a cool, sheltered valley, then climbs through the old burn area. At the bentonite section, a right-hand cutoff avoids the steepest stairs and rejoins near post 11. Post 12's spur reaches the clinker overlook; later stops pass the grassland and the exposed clinker chimney.

A 12-foot coal seam burned underground from 1951 to 1977. As it burned away, the unsupported surface collapsed into the depression you walk through. Heat baked the rock above the seam into hard red clinker. Farther along, erosion exposed a vertical clinker chimney where fire once followed cracks in the hillside. The coal is no longer burning, but its footprint still shapes the ground here.

The pale clay is bentonite, formed from volcanic ash that settled in wet ground about 55 million years ago. It looks crumbly when dry and turns sticky and slick when wet, so the short route can be awkward after rain. The numbered stops also point out how the landscape changes between dry, sun-facing slopes and protected north-facing slopes with Rocky Mountain juniper. Seasonal pools in the valley provide breeding habitat for western chorus frogs, which may call from April through June.

Start at the signed Coal Vein Nature Trail parking area just off Scenic Loop Drive near mile marker 20 in the South Unit. A park entrance fee applies. The overlook edges drop sharply, and the route includes steep stairs; keep back from the rims and use the cutoff if you want to avoid the steepest stair section. Watch for rattlesnakes and poison ivy. Pets are not allowed on park trails. For a photo, include the red clinker caprock with the pale badlands beyond it.