If you’ve never been to Stehekin, it takes some time to get to. Lying at the head of Lake Chelan, Stehekin is only accessible on foot, by boat, or plane. I’ve traveled in and out many times over Lake Chelan in the past year and each time, it gave me time to witness the climatic, topographic, and glacial changes that make this area biologically diverse.

Upper Lake Chelan and the lower Stehekin River valley seen from a ridge above Rainbow Creek.

Lake Chelan is cleaved into the heart of the North Cascades and is one of the more spectacular places in the area, biologically and geologically. Most people who arrive in Stehekin in Lake Chelan National Recreation Area do so via ferry. When the ferry motors away from Fields Point Landing, about one third the distance from Chelan to Stehekin, it leaves a relatively dry habitat with sparse tree cover, but this can look lush compared to areas farther down lake. At the lake’s outlet, the town of Chelan receives only 11.4 inches (29 cm) of precipitation per year. It is a downright arid place.

Sparse vegetation along the lower half of the lake is the result of an arid climate with hot, dry summers.

As the boat continues up lake, stands of ponderosa pine and Douglas-fir slowly thicken. At the elevation of the lake (1,100 feet, 335 meters) however, several factors continue to limit tree growth even along the lake’s upper reaches. Fires frequently burn the slopes while bare rock and sheer walls inhibit soil formation. Summer drought is common with scant rain and hot, dry temperatures that bake the lake’s western and south facing slopes. During spring, the mountainsides are flush with water from snow melt, but in late July and August the soil will become so desiccated it rises like powder under your footsteps.

In 2015, wildfires burned large areas near Lucerne, a small village on the lake.

With ample snow melt, water is easy to find on the mountainsides next to the lake. In mid to late summer however, many of the gullies will become completely dry.

The North Cascades are famous for prodigious snowfall and plenty still clings to the mountains at this time of year. During the last glacial maximum, nearly the whole lake basin was filled with a glacier that carved it into a land-locked, steep-walled fjord.

In its middle reaches, Lake Chelan plunges to great depths. The mountain topography on either side of the valley restricted the glaciers outward flow, but not its forward movement. The tight topographic pinch created by the mountains enhanced downward erosion by the glacier. The lake basin, averaging only a mile wide over 50 miles, was greatly over-deepened, even reaching below sea level. At its deepest point the lake is almost 1500 feet (456 meters) deep. (More info about Lake Chelan’s underwater topography.)

The upper basin of Lake Chelan is its deepest and most voluminous. Near mile 16 on the horizontal axis lies a submerged glacial moraine.

The steep mountain topography continues underneath the lake.

Sheer cliffs plunge steeply into Lake Chelan above the deepest areas of the lake. Below the boat on which I stand, the water is over 1,000 feet deep.

The volume of the former glaciers is apparent by looking at the shape of the mountains. Where glaciers overran the mountains, the ridges and peaks are smoothed over and somewhat rounded. Mountains that were tall enough to escape complete glaciation remain craggy and jagged. Measured perpendicularly from the deepest area on the lake to the crest of nearby mountains, vertical relief can reach 9,000 feet (2,744 m) and glaciers filled most of the space in between.

Knife-edged ridges and peaks were not completely glaciated. Glacier ice eroded lower ridges, smoothing them over.

Looking at a map of Washington before I arrived here, I didn’t fully understand or appreciate the area’s diversity or its glacial story. Here, arid adapted species like sagebrush can live on hot, dry rocky outcrops just a short distance away from a cool, moist ravine with western red cedar and thimbleberry. Glaciers left their mark up and down the lake, accentuating topography even further. Lake Chelan is Washington’s inland fjord surrounded by, perhaps, the most diverse habitats in the whole North Cascades ecosystem.