For visitors who can’t quite manage the trek out to Bumpass Hell [1], the Sulphur Works offer a peak at the geothermal features of Lassen right on the main road. A boardwalk runs along the road and a parking area is nearby, allowing visitors to get out of their cars to examine the loud boiling mud pots and small steaming stream here.
The mud pots both look and sound like a washing machine, sending up steam and occasional bursts of boiling water. Keep hold of your children!
As of the writing of this guide, the small loop trail and longer path out to Ridge Lake were closed. Check with the rangers on the status of these trails during your visit.
Links:
[1] http://www.moon.com/destinations/california/lake-tahoe-and-the-northern-sierra/lassen-volcanic-national-park/sights/bumpass-hell