DEVELOPMENT OF THE 1990 KALAPANA FLOW-FIELD, KILAUEA VOLCANO, HAWAII

The 1990 Kalapana flow field is a complex patchwork of tube-fed pahoeh oe flows erupted from the Kupaianaha vent at a low effusion rate (appr oximately 3.5 m3/s). These flows accumulated over an 11-month period o n the coastal plain of Kilauea Volcano, where the pre-eruption slope a ngle was less than 2-degrees. The composite field thickened by the add ition of new flows to its surface, as well as by inflation of these fl ows and flows emplaced earlier. Two major flow types were identified d uring the development of the flow field: large primary flows and small er breakouts that extruded from inflated primary flows. Primary flows advanced more quickly and covered new land at a much higher rate than breakouts. The cumulative area covered by breakouts exceeded that of p rimary flows, although breakouts frequently covered areas already buri ed by recent flows. Lava tubes established within primary flows were l onger-lived than those formed within breakouts and were often reoccupi ed by lava after a brief hiatus in supply; tubes within breakouts were never reoccupied once the supply was interrupted. During intervals of steady supply from the vent, the daily areal coverage by lava in Kala pana was constant, whereas the forward advance of the flows was sporad ic. This implies that planimetric area, rather than flow length, provi des the best indicator of effusion rate for pahoehoe flow fields that form on low-angle slopes.