A place of beauty, yet volatile and violent. Among the clear lakes, grazing mule deer, and fields of wildflowers sleep all four types of volcanoes—cinder cones; shields, which spew lava in all directions; composite, which emit lava, ash, cinders, and blocks; and plug domes, whose lava piles up inside the crater. More than 20 years before Lassen Peak last blew its plug, Muir wrote: “Miles of its flanks are reeking and bubbling with hot springs, many of them so boisterous and sulphurous they seem ever ready to become spouting geysers ...”