This project involves drilling a 600 m pilot hole preparatory to core-drilling a 4.5 km hole in the vicinity of Hilo, Hawaii, and characterizing the returned core samples and well site using an array of modern geochemical, petrological, and geophysical techniques. The principal objectives of the holes is to obtain a nearly continuous, ordered record of the output of an oceanic volcano over a long interval of its main shield-building phase of activity. Only small fractions of the output and history of any individual Hawaiian volcano are accessible through surface exposures and it is unlikely that the interiors of these volcanoes will ever be exposed except by deep drilling. The primary scientific questions to be addressed concern the nature of hot spots, in particular, the composition and origin of the "plumes" they may represent, and how the upwelling material interacts with the lithosphere and surrounding mantle material on time scales of 105 to 106 years. These problems are intimately related to the nature of magma isotopic compositions and ages of the lavas encountered in the drill core, and to invert this geochemical time series in conjunction with dynamical models for plume behavior and melt generation to develop a comprehensive model for the dynamics of the hot spot phenomenon at Hawaii. Other major scientific questions that can be addressed through study of a unique sample suite of the sort expected from drilling include: How long is an individual Hawaiian volcano active? What is the nature of the submarine-subaerial transition and of the submarine section of a major oceanic volcano? What are the mechanisms of growth and the rate of growth of a Hawaii volcano and of subsidence due to the load on the lithosphere from the growing volcano? What are the magnetic properties of oceanic volcanic rocks as a function of depth and petrology and how do these relate to magnetic surveys near seamounts? What is the thermal structure and state of preservation of igneous features in the interiors of the flanks of Hawaiian volcanoes far from rift zones.
