Hawaiian volcanoes can erupt either at their summits or on their flanks.
Young Hawaiian volcanoes, such as Kilauea and Mauna Loa, have summit calderas. A caldera is a crater several miles in diameter that forms as the result of collapse when magma drains from beneath the summit. Summit eruptions of Kilauea and Mauna Loa occur within or near their calderas. Flank eruptions usually take place along rift zones, which are highly fractured zones of weakness within the volcano. Rift zones typically extend from the summit of a volcano toward the coastline and may continue for many miles under the sea.