Is distilled water lava?
Executive summary
Distilled water is not lava in the conventional, geological sense used by volcanologists and most scientists: lava denotes molten rock erupted from beneath a planetary crust, usually at hundreds to over a thousand degrees Celsius and with rock-like chemistry and viscosity [1]. That said, a narrow, formalist argument—rooted in how one defines “molten” and “natural minerals”—has been advanced in popular science discussion and commentary to suggest liquid water could be counted as a kind of “lava” under the broadest possible definition, and analogous eruptive processes occur as cryovolcanism on icy worlds [2] [3].
1. What volcanology and reference texts mean by “lava”
Standard definitions treat lava as molten or partially molten rock (magma) expelled onto a planet’s surface, characterized by silicate chemistry, high temperatures (commonly ~800–1,200 °C for terrestrial lavas), and non-Newtonian viscosities greatly higher than water’s; these physical and chemical traits distinguish lava from ordinary liquids like water [1]. Wikipedia’s entry explicitly ties lava to molten rock and records typical eruption temperatures and viscosities that are orders of magnitude different from liquid water [1].
2. The formalist counterargument: language, minerals and molten ice
Some writers and commentators have noted that, in the broadest geological framing, “lava” might be defined as any natural substance that has been melted and flows from beneath a crust, and that ice is a mineral—so liquid water could be seen as “molten ice” under that semantic chain [2]. The Star’s QuickCheck piece summarizes the thought experiment: by stretching the technical definition to “molten natural substance erupting from beneath a crust,” water can be categorized as lava, though this is unconventional and confusing in practice [2].
3. Why that semantic stretch is misleading for practical science
Equating distilled water with lava ignores fundamental differences in chemistry, temperature, rheology and geologic origin: terrestrial lavas are silicate melts with dissolved volatiles and high viscosities that shape volcanic landforms, whereas water is a low-viscosity, Newtonian fluid with vastly lower melting and boiling points and different erosive behaviors [1] [4] [5]. Comparative sources emphasize that even the most fluid terrestrial lavas flow much slower and are more viscous and denser than water, which alters how they erode and build landscapes [1] [5].
4. Where the “water as lava” idea has useful applications—cryovolcanism and planetary geology
Geoscience commentary and planetary studies point out that on icy bodies in the outer solar system, eruptive flows of water, ammonia or hydrocarbons—so-called cryovolcanism—functionally play the role lava does on Earth; there, molten or liquid volatiles erupt and build surface features, so calling those flows “lava” in a planetary-contextual sense is defensible [3]. Geoscientist.online explains that thought experiments about ice as a monomineralic rock and water as molten ice have traction in discussing icy moons, where the physics and chemistry legitimately differ from Earth [3].
5. Verdict and practical guidance for communication
For clarity and accuracy in Earth-focused geology, distilled water is not lava and calling it so is likely to mislead; mainstream publications and volcanology resources separate molten rock (lava) from liquid water on the basis of composition, origin and physical behavior [1] [4]. However, acknowledging the formalist framing and the legitimate usage of “lava” analogues in cryovolcanism is important for nuanced scientific conversation—sources advocating the semantic stretch make that caveat explicit even as they call the idea unconventional [2] [3].