Deep and rapid thermo-mechanical erosion by a small-volume lava flow

•Lava flows can erode into the surfaces (substrates) upon which they flow.•A lava flow at Momotombo volcano, Nicaragua incised 30m into the cone as it emplaced.•This flow thermo-mechanically eroded by heating the substrate and reducing hardness.•The substrate's glass transition temperature is the point at which erosion begins.•Levees do not bound incised parts of the channel, useful for planetary applications.