View is from the north caldera rim toward the southwest. Halema`uma`u pit crater (top left) marks the location of the principal caldera vent active between about 1838 and 1924, during which time overflows from the crater built a low shield and episodic collapses formed a deep pit crater. Today, the low shield gradually rises about 35 m from the north caldera floor (bottom), which is covered by lava flows mainly erupted from Halema`uma`u in 1919.
The steep cliffs of the west caldera wall (upper right) form Uwekahuna Bluff, the highest point along the rim of Kilauea Caldera. The bluff rises about 135 m from the caldera floor. The buildings atop Uwekahuna Bluff house the USGS's Hawaiian Volcano Observatory and the Hawai`i Volcanoes National Park's Jaggar Museum.When viewed in 1823 by the Reverend William Ellis, the first person to describe the marvelous scene in writing, the caldera floor was about four times as deep as it is today -- an erupting inner "pit" was estimated to be about 540 m below the west caldera rim (an earlier estimate of 275 m depth was revised in 1997 based on evaluation of survey data; see reference below).
Since the most recent caldera-collapse event sometime before A.D. 1790, activity within the caldera has chiefly been rapid infilling of lava and a few intermittent collapses of the caldera floor and Halema`uma`u. The most recent eruption in the caldera was on September 25, 1982.
The modern caldera measures about 3.25 by 4.75 km across, but arcuate faults farther out define one or more previous calderas as wide as 6 km.
Mastin, L.G., 1997, Evidence for water influx from a caldera lake during the explosive hydromagmatic eruption of 1790, Kilauea volcano, Hawaii: Journal of Geophysical Research, v. 102, no. B9, p. 20,093-20,109.