The Uwekahuna Ash was erupted about 1,500 years ago and may be related to an older caldera that filled with lava prior to the development of the present caldera. The Keanakakoi Ash was erupted during weeks or months of activity in 1790. The early activity was driven by degassing magma that interacted with groundwater. Later eruptions were driven by steam explosions. The warriors were killed near the end of the eruption by what geologists call a base surge .
Surges are gas-rich and have little volcanic material.
Note that these explosive eruptions are infrequent.