Steaming sulphur vents, splattering mud pots, boiling springs—these feisty hydrothermal features prove that the earth is very much alive. Lassen Volcanic National Park’s signature volcano, Lassen Peak, blew its top in 1914 and its outbursts continued for three years. Now it’s dormant, and trails and overlooks let you explore geological wonders amid a tranquil landscape of dense woods and sparkling lakes. Feel the heat at Sulphur Works or Bumpass Hell and then climb a cinder cone or go kayaking.