Please note that this is the Narutopedia's article on the combination of the earth and fire natures. If you are looking for the article on the release based on physical energy that governs life then you should head to Yōton.
Lava Release (熔遁; 溶遁, Yōton, Viz: Corrosion Style" or "Lava Style) is a combined nature transformationkekkei genkai made up of techniques that mix fire and earth-based chakra to create volcanic materials such as lava or rubber in different properties and usages.
Mei Terumī of Kirigakure's Lava Release takes the form of a strong acidic mud which can be used offensively and defensively.
Kurotsuchi of Iwagakure's Lava Release takes the form of quicklime, which is a corrosive substance. Several other Iwagakure shinobi also have shown the ability to use this same variation of Lava Release. In the anime, Kyūsuke of Amegakure's Lava Release also takes the same form of quicklime.
Dodai of Kumogakure's Lava Release takes the form of vulcanised rubber-like material.
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.