page_title: Lava delta
section_title: Formation
hierarchical_section_title: Lava delta / Formation
caption_attribution_description: English: Aerial view of the active lava delta at Kamoamoa, Kilauea. Steam plumes mark the points at which lava carried in a series of lava tubes on the delta top reach the sea.
context_page_description: Lava deltas, similar to river deltas form wherever sufficient sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the adjacent seabed topography such that the flow can move further offshore sub-aerially. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism.
context_section_description: 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. 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. 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 viscosity Pahoehoe type flows and the lava reaches the sea via a system of small lava tubes, their entry into the water being marked by a series of steam plumes.
caption: Aerial view of Kamoamoa lava delta forming, Kilauea
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