The first 3.5 miles (5.6 km) of this trail is a wide, gravel path through the forest. After that point the trail narrows and becomes a fun mix of entertaining terrain and challenges that'll force you to walk. Some stretches are commonly brushy, eroding into the water, or even completely flooded during periods of heavy rain or snow/ice melt.
Watch out for walkers and runners on this trail, in addition to other bikers and the ever-present possibility of surprise wildlife encounters.
Toward the end of the trail, there is a steep uphill that you might need to push your bike up. But you'll be rewarded with better views of the glacier if you do so (and if the trail isn't too washed out).