Mental note: next time bring a respirator and an extra liter of water — make that a moon buggy and a space suit.

he surface of the riverbed is an extremely fine sand, two to three inches deep. We can barely pull five miles an hour, and an array of cars, trucks, ATVs and dirtbikes circle us like vultures.

Jim Creek isn't far from the Thunderdome. There's no bridge, and it's about three feet maximum depth at its shallowest. We spend some time watching cars cross, gauging its depth. A Gremlin takes a shot at the crossing, gets up a good deal of speed, splashes into the water, and barely floats to its destination. The occupants cheer loudly.

A Jeep filled with five standing people in the back, holding onto the rollbars, approaches the river. These guys are incredible — totally buff, shirtless, holding beers and screaming in glee about the crossing they're about to make. They ride it out magnificently, though the truck seems to sustain some damage. To the damage report of a passenger, the driver responds, "Mellow out, dude."

Our confidence shaken, it takes the urging of locals before we attempt the crossing.

The sand has clogged and dried out one of the bike's components to the point where they no longer function. Though a pennyroyal-based organic bug repellent solves the problem and enhances the group's smell, we are desperate to get out of the sand. We climb the large sand dune that forms a border between forest and bank. The network of ATV trails here is extensive, though most drivers seem to thankfully prefer the sand.

There's some great riding to be had back here. The trails are technical, the hills laid out in the fashion of a mellow roller coaster — short ups and downs with lots of obstacles and banked hairpin turns. The surface varies from rocks to torn-up tundra. And there's a bit less dust.

Wild roses grow in abundance. They are dry, with no leaves or flowers. The nuclear winter took care of that. Reduced to their thorny essence, the proliferation of roses proves most difficult as we wind our way through a complex network of increasingly overgrown trails. Eventually they become impassable. We find ourselves in that all-too-common rut of entering increasingly more terrible terrain — convinced that going back is too hellish and that the end of the rainbow must be soon to come.