Halema'uma'u Crater - From the sign at the site:
Kilauea Caldera has undergone dramatic change since the 1823 visit of William Ellis, the first Western explorer. In that year, the caldera was almost 1000 feet deep, twice as deep as it is today. An inner pit, several miles across, contained raging lakes of molten lava. Throuightout the 19th century, these lakes repeatedly overflowed, building up the level of the floor halfway to the brim. On 4 occasions this process of construction was suddenly reversed by collapses involving almost the entire caldera floor.