⇐ ⇑ ⇒ HI-RES Volcanoes National Park, Thursday 24th February Halema`uma`u within Kilauea Caldera from Kilauea Overlook. Halema`uma`u is the most recently active part of the caldera, and contained a lava lake from 1905 until a phreatic explosion in 1924, since when it has been filling in.