Aerial view of lava delta (center, left of volcanic fume) growing seaward at Kamoamoa on Kilauea Volcano, Hawaii. The new land is about 450 m long and 180 m wide (from sea to old shoreline). Credit: C. Heliker / U.S. Geological Survey.
A lava delta is a wide fan-shaped area of new land formed from lava that has entered the sea. Such new land is usually built on sloping layers of loose lava fragments and flows. On steep submarine slopes, these layers of debris are unstable and often lead to the sudden collapse of lava deltas into the sea.
The partial collapse of a lava delta can be a hazard for people who venture too close to lava entering the ocean. For example, on April 19, 1993, one person was killed and 16 others injured when a section of an active lava delta on which they were standing collapsed into the sea at Kilauea Volcano, Hawaii.