Hornitos are conical, or pipe-like, structures built up by

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

spattering or being ejected through an opening in the crust of a

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

. Hornitos are similar to

spatter cone Volcanic cones are among the simplest volcano, volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone (geometry), cone with a central crater. Volcanic cones are of different types, depen ...

s but are rootless, meaning they were once a source of lava but that source was not directly associated with a true vent or

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

source. They are usually created by the slow upwelling of fluid lava through the roof of a

lava tube A lava tube, more rarely called a pyroduct, is a 'roofed conduit through which molten lava travels away from its vent'. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. La ...

, and are often associated with

pahoehoe Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or unde ...

lavas of

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

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 grow and exceed 10 meters in height. Some classic examples of hornitos have been described, or depicted, from volcanoes including

El Jorullo El Jorullo is a cinder cone volcano in Michoacán, central Mexico, on the southwest slope of the central plateau, southeast of Uruapan in an area known as the Michoacán-Guanajuato volcanic field. It is about east-northeast of La Huacana. I ...

, Mexico which was visited by

Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 1769 – 6 May 1859) was a German polymath, geographer, natural history, naturalist, List of explorers, explorer, and proponent of Romanticism, Romantic philosophy and Romanticism ...

in 1803; Kilauea Hawaii; and

Oldoinyo Lengai Ol Doinyo Lengai is an active volcano in northern Tanzania. It consists of a volcanic cone with two craters, the northern of which has erupted during historical time. Uniquely for volcanoes on Earth, it has erupted natrocarbonatite, an unusually ...

, Tanzania. The term hornito comes from the Spanish, meaning 'little oven'; a reference to the way that hornitos might appear to 'smoke' when they are active.

References

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External links

Video of Hornito
Volcanic landforms