Intro
The Climb:
North Twin is the second-highest peak in the rugged Twin Sisters Range, located about 9 miles southwest of the glaciated giant, Mount Baker. On a clear day, the summit offers an unobstructed view of the nearby volcano—but what truly sets it apart is the exceptional quality of the scrambling. The range is composed of dunite, a rare ultramafic rock made almost entirely of olivine. From a climbing perspective, this coarse-grained rock is incredibly grippy—almost like natural sandpaper. North Twin boasts roughly 1,500 vertical feet of sustained Class 3 scrambling on this solid, textured rock. The only drawback is the moderately long approach, made more tedious by the closure of the old logging road. It is nearly 5,500 vertical feel from where you park your car to the summit. Currently, the most efficient option is to bike in—the 5+ miles and 2,500+ vertical feet of uphill riding is a serious grunt, but the bike down is much quicker than hiking.
Geology:
Twin Sisters Mountain is very unique in it's geology. All but the last sentence of the following paragraph is taken verbatim from Roadside Geology of Washington by David Alt and Donald Hyndman, pg 265: "Twin Sisters Mountain is one of the most extraordinary bodies of rock in the the country. The mountain, which is about 10 miles long and 3 miles wide, is a solid mass of an extremely rare rock called dunite, which consists almost entirely of the mineral olivine. Dunite properly belongs in the mantle, and is greatly out of place in a continent. The fresh rock is green, the color of olivine, but it weathers to the rusty brown color that makes the ragged top of Twin Sisters Mountains conspicuous from a great distance. This rock is solid and grippy, and great fun for climbing."
