lake toba, north sumatra, indonesia

activity amazing andesite around asia awesome berastagi centre climbing crater crystalline deepest deleng depth discolouration dolok enormous eruption gases geothermal goals gunung high hiker hiking hot indonesia indonesian island karo lake lakes largest like meters mount mountain natural nature north one outdors plateau pleistoceneholocene regency seepage sibayak sinaboen sinaboeng sinabuna sinabung southeast springs steam stratovolcano sulfur sulfurous sumatra toba travel traveler vents volcano wonders world