This canyon is unreal.
The rock is maroonish brown with tan intrusions (wiki) that look like lightning. The depths of the canyon are a shaded muddy black. The Gunnison River was only viewable from certain points along the rim and, it stood out against the darkness as a roiling sliver of green tinted turbulence. Its roar could be heard.
In the upper canyon ravens effortlessly strafe the sun bathed walls.
Erosion has created thin stone fins perpendicular to the canyon, and the raven shadows bounce out on these fins and dive into the crevasses. The raven’s throaty call echos up from the depths even more wretched than the original. Lower in the canyon swallows and swifts the size of stout cigars dart around snapping up early evening insects. A handful flew by me at eye level before diving down to the feast. Their wing beats are sharp enough to be heard over the wind and river.
This canyon is like nothing I’ve ever seen.
To quote geologist Wallace Hansen,
“Several western canyons exceed the Black Canyon in overall size. Some are longer, some are deeper, some are narrower, and a few have walls as steep. But no other canyon in North America combines the depth, narrowness, sheerness, and somber countenance of the Black Canyon of the Gunnison”.
In 48 miles the Black Canyon of the Gunnison looses more elevation than the 1,500 miles of the Mississippi from Minnesota to the Gulf of Mexico.
But why so steep? Shouldn’t the river just go around?
The way I understand it is like this: 1.7 billion years ago the rock that would become the strong walls of the canyon was formed as metamorphic rock. The original brown (gneiss and schist) layer solidified and then fractured allowing the tan (pegmatite) intrusion dikes to enter the cracks and solidify. Fast forward more than 1.6 billion years (1/3 the age of the earth), and a period of volcanic activity created a walled off “cul-de-sac” watershed with the only outlet being toward the north. From the foothills of the volcanoes the watershed sloped gently, and the general route of the Gunnison River was laid down as an unassuming valley. Then as recently as 2-3 million years ago the area underwent broad uplift. The slope of the watershed increased, and the river continued to cut deeper and deeper as the original metamorphic formation was thrust upwards. The Gunnison River dug down into the rising rock at a rate of 1″ per 100 years [math check: 2,000,000 years * (1 inch / 100 yrs) * (1 foot / 12 inch) = 1,667 feet of erosion over 2 million years].
The interesting part is that if the predecessor to the Gunnison river hadn’t begun to erode the blueprint of the Black Canyon before the uplift, the river likely would have followed a path of least resistance around the uplift. However, as the uplift occurred the path of least resistance continued to be the route originally determined by the gentle slope.
I hiked down into the canyon the next day. It was steep, loose, sketchy, and totally worth it.
That’s all folks! Have a juniper in silhouette!