Coldwater Lake / Mount Margaret

The ride as described here is out and back, about 16 miles total:

You'll start off riding though a cool forest, but will soon break out of the shade into the Mt. St. Helens blast zone. The trail begins climbing right out of the parking lot as it switchbacks up to the ridge above Coldwater lake. The trail levels off briefly as you enjoy a spectacular view over the lake, and you pedal past logging equipment destroyed in the 1980 blast. Once you leave the lake, you'll begin climbing again into the St. Helens blast zone. Here the trail becomes more primitive, loose, sandy and overgrown with brush in places. This is truely a backcountry ride! The trail will continue climbing past St. Helens Lake, The Dome and towards the high point at Mt. Margaret where you turn around and come back.

Some do this ride from the other side, starting at the Norway Pass trailhead and riding Boundary Trail 1 over Norway Pass to Mt. Margaret. If you do this ride, be prepared for variable trail conditions, a lot of bike pushing, some exposure, and on a clear day, the most amazing views you have ever seen. Once in the blast zone, there is no shade. Bring plenty of water! As a bonus, the ride back to the trailhead is mostly downhill, hang onto your brakes - fun, fun fun!