Effusive eruptions began to fill the Powers Caldera with lava about 1,000 years ago, breaking the 1,200-year-long interval dominated by explosive eruptions. Lava completely filled the Powers Caldera and then overtopped its rim, solidifying the structure. This was followed by a period of voluminous tube-fed lava flows from 1000 to 1500 CE (including the ʻAilāʻau eruption), with the modern smaller Kīlauea Caldera having formed inside the buried Powers Caldera in about 1470 CE.