The North Cascades

This pullout on the highway is the front-row seat, set on the flank of Ruby Mountain with the whole reservoir spread out below. It is the easiest place anywhere to meet the color head-on and understand it. The lake sits at around twelve hundred feet, ringed by peaks that climb thousands of feet on every side, and its surface can range from pale milk to deep jade depending on the light. That range is the tell. The green is not a pigment dissolved in the water and not the sky reflected off it — it is sunlight scattering off countless grains of rock, ground so fine by glaciers that they never settle out. On a clear day the color is almost too much to believe; under heavy cloud the same water goes gray. Nothing about the lake has changed but the light it has to work with.

The road crosses the Skagit here on the crest of Diablo Dam, and the setting explains why a dam could be built at all. The builders drove it into Diablo Canyon, a gorge of hard, ancient rock whose vertical walls stand barely a hundred feet apart and rise well over a hundred feet from the old riverbed. Work began in 1927 and the dam was closed by 1930, though it did not start making power until several years later. A slot that narrow and that sheer is not the ordinary work of a river, which tends to widen and wander as it cuts. It is the signature of ice: a glacier filling the valley and grinding straight down through hard rock leaves a steep, narrow trench behind. The engineers found the hard part already done for them — all they had to do was close a gap the glacier had cut and walled in solid stone.

A trail drops off the highway to the foot of Ross Dam, a tall, thin curve of concrete that holds back Ross Lake — a reservoir that runs some twenty miles north, all the way into British Columbia. The walk down and back is the price of admission, and it puts you inside the glacier’s trough rather than looking down at it. What the reservoir floods is another deep, straight reach of the Skagit, cut by the same ice that shaped the lake below. The higher and farther upstream you go here, the more plainly you are traveling up the inside of a valley a glacier plowed — long, straight, and steep-walled, the opposite of the meandering course a river carves on its own. The dam is young; the shape of the canyon it fills is old, and the ice that made it is only just out of sight in the peaks.

Ruby Mountain is the great wall on the east side of the lake; the highway overlook sits right at its foot. From the water its summit stands more than six thousand feet up, and it reaches that height in only about two miles — a rise so steep it reads as a wall rather than a slope. The mountain also sits on a divide: rain and snowmelt off its east side run to Ross Lake by one creek, while its west side drains straight down to Diablo Lake by another. You do not need to climb it to read it, and climbing it is a serious, route-finding undertaking best left to those equipped for it. The lesson is in the steepness. Slopes this abrupt are not the patient work of streams; they are the over-steepened walls a glacier leaves when it grinds down a valley floor, undercuts the sides, and then melts away, leaving the rock standing far too steep to be the work of water.

Pinnacle Peak is one of the sharp summits that rise almost straight out of the lake on its south side, notable less for its height than for how abruptly it stands above everything around it. The way up begins near Diablo Dam and climbs a steep spur toward Colonial Glacier — a patch of living ice still tucked in the high rock. Reaching the ice is real mountaineering — steep, trackless, and only for those with the skills and gear for it — but it closes the loop the whole note has been drawing. Everything you saw at the water’s edge, every shade of impossible green, begins as stone under a glacier that is still slowly, patiently at work in these peaks.

Paul Bunyans Stump is the blunt, flat-topped tower on the ridgeline south of the lake, its odd name a bit of local humor for a summit shaped like a giant’s leftover stump. Like its neighbors, it stands almost directly above the water, part of the chain of peaks that walls the lake in on that side. What is worth noticing is the near-total absence of anything between the summits and the lake — no gentle foothills, no long ramp of debris, just rock dropping toward water. That is how a filled valley looks after the ice leaves. A glacier thick enough to reach these heights scours the walls clean as it moves, and when it melts the peaks are left standing right at the shoreline, with nothing to soften the drop. Reaching the summit itself is a climber’s project; the point it makes can be read from the lake or the road below.