"The eruption of October 5-6, 1963, occurred along an 8-mile section of the central part of the east rift zone of Kilauea Volcano. About 9 million cubic yards of lava was erupted from more than 30 fissures which show a slight right-offset en echelon pattern; the new lava covered an area of 1.3 square miles. A few hours before the actual outbreak, the summit of Kilauea began to subside, and strong harmonic tremor and earthquakes commenced at both the summit and the site of the later activity near Napau Crater. These phenomena were apparently caused by subsurface flow of magma from the summit reservoir through the rift zone conduits to the eruptive vents 8 miles distant. The lava of the eruption is a tholeiitic basalt with an average of 5.6 percent olivine. In general, lavas that erupted toward the eastern end of the eruptive zone are richer in olivine. These lavas, like others that erupted in historic times on the rift zone, show a slight differentiation when compared with lavas that erupted from the summit. The differentiation, apparently caused by cooling and crystallization within the rift zone, can be measured by the ratio (CaO [Calcium oxide]/FeO [Iron II oxide] + 0.9 Fe2O3 [Iron III oxide]), which is greater than 1 for summit lavas and which decreases systematically for lavas that erupted progressively eastward along the rift zone."
Geological Survey Professional Paper 614-C
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