Lava Release (熔遁; 溶遁, Yōton; Viz "Corrosion Style" or "Lava Style") is an advanced naturekekkei genkai that combines fire and earth-based chakra to create lava and related substances that can serve multi-faceted purposes.
When Rōshi's Lava Release is first referred to, the kanji 熔, with the radical for "fire" (火), is used. In later references when Mei's is used, the kanji 溶, with the radical for "water" (水), is used instead. When both Kurotsuchi and Dodai used it, it was once again with the fire radical. This seems to indicate that the Lava Release from Iwagakure and Kumogakure uses the fire radical, while the Lava Release from Kirigakure uses the water radical. However, in the data and fan books, both kanji have been used to refer to Rōshi's Lava Release.
Nowadays, the two kanji are synonyms and used interchangeably, with 溶 being the more common variant. However, there seems to be a subtle difference in meaning between the two. The kanji with the fire radical seems to be used more often in words relating to metal and other solids, whereas the kanji with the water radical is more often used in words relating to liquids.
This kekkei genkai element shows the most different users with no known blood connection to each other.