Powers Caldera

[1][2] It is the precursor to the modern but smaller Kīlauea Caldera, having formed about 2,200 years ago as a result of powerful phreatomagmatic eruptions.

[1] These explosive eruptions lasted for a period of about 1,200 years, during which time the Uwēkahuna Ash Member was deposited.

[1][3] Sometime between 850 and 950 CE, the most powerful explosive eruption sent rocks weighing 9.7 lb (4.4 kg) at least 3 mi (4.8 km) from the summit.

This implies that a large depression existed in the summit area of Kīlauea prior to deposition of the Uwēkahuna Ash Member.

Powers, who conducted a careful field study of the Uwēkahuna Ash Member in 1948 and inferred the existence of the caldera.