Red Butte - Red Slot Loop
This little loop lies in the desert about 15 miles southeast of Green River. It offers a mix of beautiful slickrock, undulating red desert, and a slot canyon downhill run. The area is primarily a motorcycle paradise, but there's good stuff for mountain bikes here too. You can also do most of this loop as a variation to the east end of Mary's Trail. The loop is 6 miles in length. There will be 500 vertical feet of total climbing. 200 feet of the altitude change will be on the dirt-road return, and 300 on breathtaking Entrada sandstone on Red Butte. The loop uses the trails Red Butte, Red Rock, and Red Slot, then it returns via Red Wash Road. Yeah, there's a lot of red dirt.
Riding notes, counterclockwise loop from
west end slickrock near cattleguard:

0.0   Southbound on Red Wash Road
N38 45.194 W110 01.650
1.7   Pass Red Slot trail on L
N38 44.934 W110 00.254
1.9   Ten Mile road joins on R
2.1    L on Red Butte N38 45.103 W109 59.845
2.2    Cross Enduro Loop
3.6    Drop off sandstone, L on ST
( Red Rock trail ) N38 45.682 W110 00.276
3.9    Fork R (stay on Red Rock)
N38 45.447 W110 00.231
4.7    Keep R (alternate rejoins)
N38 45.284 W110 00.531
4.9    R on Red Slot N38 45.156 W110 00.651
6.0    At cattleguard, L to parking
Getting there:
On I-70, drive about 13 miles east of Green River. Take the Floy (175) exit. Turn right (south). The pavement rapidly turns to dirt. This is the Ruby Ranch Road At mile 4.2, turn left to Blue Hills Road. Go 3.7 miles, then turn right (south) toward Ten Mile Point. The Enduro Loop will cross a bit later, then will cross again. Drive past the sandy east entry to Mary's trail at mile 8.5 from the highway. At mile 14.1, you reach the entry to Red Butte. Park here at N38 45.194 W110 01.650, or continue to mile 16 and park in the slickrock area, retracing your vehicle's path back to Red Butte.

Trail conditions and alignments will change. Use this guide at your own risk. Copyright 2013 UtahMountainBiking.com

From the west: If you're camping in the White Wash sand dunes area (reached via Ruby Ranch Road), you may wonder if you can bike directly to this trail. Well, yes. But even by the most rock-and-dirt intensive path, you'll push your bike through about 1/10 mile of sand as you cross White Wash. I do NOT recommend trying to drive down and through the wash. I've done it; it's not pretty. Navigate to the far south end, where the connector drops from the bluff after the last parking zone. When you reach sand, hoof straight across bearing straight south. You'll encounter a (still sandy-sloppy but sometimes rideable) road along the fence. Continue on Red Wash Road until 4.2 miles since you dropped off the bluff. Here you'll find the cattleguard that marks the far west end of the loop. Continue 2 miles on the road to reach Red Butte.