Lava delta

Lava deltas, similar to

Lava deltas are found mainly associated with volcanic islands, particularly those formed at hotspots as they produce the necessary effusive basaltic flows.

The largest lava delta systems known are associated with formation of volcanic type

When a sub-aerial lava flow reaches the ocean (or other large body of water), contact with the water causes both rapid cooling of the lava and steam explosions that fragment it. The glassy fragments that are formed, known as hyaloclastites, fall down to the seabed forming foresets. As the seabed topography becomes infilled, the subaerial flow is able to build out. The process continues as long as the lava supply is maintained, creating a lava bench. A lava bench is a volcanic landform with a horizontal surface raised above the level of the surrounding area.^[5] The Hawaiian islands are an example of land that was formed this way, and the Big Island is currently still expanding due to lava benches.^[6] The Kilauea Volcano releases lava that flows down the slope of the volcano and eventually encounters the ocean; this lava flow hardens when it comes into contact with the significantly cooler water of the ocean and forms an unstable lava bench. Eventually, when the material beneath the lava bench stabilizes, it becomes stable land that has been added to the island.

Most lava deltas are formed by relatively low

Collapse of the frontal part of lava deltas is common during their formation, representing a hazard for any people that are watching from a solidified part of the delta and such areas are normally marked as dangerous.[8] If a newly formed lava bench rests on sediments, it may pose hazards due to its extremely unstable structure.^[6] Oftentimes, these benches are so unstable that they collapse into the sea, exposing the water to the hot lava on the interior of the bench and releasing acres of land into the ocean.^[6] When the hot lava hits the water, violent explosions of steam can shoot large rocks and molten lava up to 300 feet (90 m) inland.^[5] These collapses are extremely dangerous because they can happen without warning, and anyone or anything on the bench will be caught in the collapse. For safety, people are advised not to walk on lava benches because of their unstable nature, and they must maintain a safe distance from the lava bench.^[9]

People standing too close to the edge of an active delta are not only at risk from being thrown in the water but from the steam explosions and the accompanying acidic clouds (laze) that result from the collapse as seawater comes into contact with the active lava tube system.

Uses

On steep-sided volcanic islands, lava deltas make attractive sites for building and many villages and towns are located on old lava deltas, such as Garachico on Tenerife.

See also

• Fajã

References