Basically, Big Bend’s desert is a rolling land of creosotebush and bunch grass. But it grows gorgeous forests of giant yucca and solid stands of lechuguilla, a barbed and bladed plant found only in the Chihuahuan Desert. Big Bend’s desert has living sand dunes, painted badlands, and petrified trees, and since it is a geologically young desert, its landforms stand in rugged relief. Igneous dikes march across plain and mountain like so many man-made stone walls. Chimney-tall stacks thrust up from barren flats as from a ruin. Volcanic ash heaps, white as snow, lean their concrete shoulders against maroon hills. The Indians used to say that after making the Earth, the Great Spirit dumped the leftover rocks on Big Bend. Heaped up, scattered wide, and piled into mountains, they lie here to this day. Since vegetation is so scant, Big Bend mountains take their shape and color from the rocks of which they are made. They loom castellated, cathedral-domed, flattopped, and razor-backed. They look red, yellow, gray, black, white, and all the shades of brown, empurpled by distance or misted over after rain in a gauzy film of green. You don’t know which is more awe-inspiring, looking up or looking down, since the mountains rise with striking suddenness between the vaulted sky and the open plain. Approaching the Chisos Mountains for the first time, you can’t believe that cars can breach those bastions, or that high inside there actually is a Basin where travelers have camped since people first gazed on these mountains. Undulating foothills fling themselves like breakers against the sheer rock cliffs. Standing atop the escarpment that walls up the Chisos South Rim, you see hills and mountains rolling like ocean waves far, far below, with here and there a gleam of silver where the river runs. Big Bend’s Rio Grande takes its moods from the weather, the season, the time of day, and the changing nature of its bed and banks. The river runs lavender-rose at sunset, brown between frost-reddened shrubs, shining like a tin roof under hazy skies, white as chopped ice where rapids churn, olive-green beneath the brooding cliffs of Old Mexico. Nobody knows which came first, the mountains or a through-flowing river, but for hundreds of river kilometers the Rio dodges and doubles, and where it cannot go around it rasps its way across the mountains. Deep-cut canyons alternate with narrow valleys walled in by towering cliffs. You can’t get across except at a handful of fords, or up steep trails at favorable stages of water. These canyons and escarpments lend Big Bend its monumental character, for as it digs, the river lays bare millions of years of Earth history. To run a desert river canyon is to penetrate the long, tortuous corridor from everlasting to everlasting: Time is here turned to stone. Imprisoned, yet wild and free, the Rio runs the ages down inside a rock-ribbed vault.