Geologic mapping of the lower east rift zone of Kilauea Volcano, Hawaii, indicates that more than 100 eruptions have extruded an estimated 10 km3 of basalt during the past 2,000 yr. Six eruptions in the past 200 yr have extruded about 1 km3. The eruptive recurrence interval has ranged from 1 to 115 yr since the middle 18th century and has averaged 20 yr or less over the past 2,000 yr.
One hundred new chemical analyses indicate that the erupted tholeiites commonly are differentiated beyond olivine control or are hybrid mixtures of differentiates with more mafic (olivine-controlled) summit magmas. The distribution of vents for differentiated lavas indicates that several large magma chambers underlie the lower east rift zone. Several workers have recognized that a chamber underlies the area near a producing well, HGP-A; petrologic and 14C data indicate that it has existed for at least 1,300 yr. Stratigraphy, petrology, and surface deformation patterns suggest that two other areas, Heiheiahulu and Kaliu, also overlie large magma chambers and appear to be favorable geothermal prospects.