The volcanic planet of Mustafar features a river composed of lava.
Lava, alternatively known as magma, represented a hazardous liquid comprised of molten rock. Frequently spewing forth from volcanoes, lava possessed immense heat, reaching temperatures of thousands of degrees. However, upon cessation of its flow, this substance underwent a cooling and solidification process, ultimately giving rise to obsidian or the formation of dark lava sand.
