Kilauea summit overflows: their ages and distribution in the Puna District, Hawai'i

The tube-fed pahoehoe lava flows covering much of the northeast flank of Ki lauea Volcano are named the 'Aila'au flows. Their eruption age, based on pu blished and six new radiocarbon dates, is approximately AD 1445. The flows have distinctive paleomagnetic directions with steep inclinations (40 degre es-50 degrees) and easterly declinations (0 degrees 10 degrees E). The lava was transported similar to 40km from the vent to the coast in long, large- diameter lava tubes; the longest tube (Kazumura Cave) reaches from near the summit to within several kilometers of the coast near Kaloli Point. The es timated volume of the 'Aila'au flow field is 5.2+/-0.8 km(3) and the erupti on that formed it probably lasted for approximately 50 years. Summit overfl ows from Kilauea may have been nearly continuous between approximately AD 1 290 and 1470, during which time a series of shields formed at and around th e summit. The 'Aila'au shield was either the youngest or the next to younge st in this series of shields. Site-mean paleomagnetic directions for lava f lows underlying the 'Aila'au flows form only six groups. These older pahoeh oe flows range in age from 2750 to < 18,000 BP, and the region was inundate d by lava flows only three times in the past 5000 years. The known interval s between eruptive events average similar to 1600 years and range from simi lar to 1250 years to >2200 years. Lava flows from most of these summit erup tions also reached the coast, but none appears as extensive as the 'Aila'au flow field. The chemistry of the melts erupted during each of these summit overflow events is remarkably similar, averaging approximately 6.3 wt.% Mg O near the coast and 6.8 wt.% MgO near the summit. The present-day caldera probably formed more recently than the eruption that formed the 'Aila'au fl ows (estimated termination ca. PLD 1470). The earliest explosive eruptions that formed the Keanakako'i Ash, which is stratigraphically above the 'Aila 'au flows, cannot be older than this age.