A hornito is a conical, or pipe-like, structure built up by lava spattering or being ejected through an opening in the crust of a lava flow. Hornitos are similar to spatter cones but are rootless, meaning they were once sources of lava, but those sources were not directly associated with true vents or magma sources. They are usually created by the slow upwelling of fluid lava through the roof of lava tubes, and are often associated with pahoehoe lavas of basaltic composition. High pressure causes lava to ooze and spatter out. The lava builds up on the surface and solidifies, creating the initial structure. Hornitos can exceed 10 meters in height.