Based on the results of a seismic refraction profile from Hilo on the northeast coast of the island of Hawaii to Kalae on the south the earth's crust in the vicinity of Kilauea volcano is found to consist of three layers. The uppermost of these layers varies in thickness from 1.2 to 2.5 km along the profile, is characterized by a P‐wave velocity of about 3 km/sec, and probably represents a series of fractured vesicular lava flows. The second layer, with a velocity of 5.3 km/sec, is much less even in thickness and probably represents the principal volcanic layer of the crust. It is 4 km thick at the Hilo end of the profile, 6 km thick at Kalae, and elsewhere fills in the crustal section between the lavas at the top of the column and the denser rock below. The third layer is 6–7 km thick, has a P‐wave velocity of about 7 km/sec, and corresponds to the principal layer of the oceanic crust. Under the summit of the volcano, this layer is faulted, with a resulting vertical component of offset equal to about 7500 meters. Depth to the Mohorovicic discontinuity is 12 km at the two ends of the profile, and the maximum crustal thickness is about 17 km at a point midway between Hilo and the Kilauea summit area. To relate this crustal profile to the over‐all structure and volcanism of Hawaii, the seismic results were compared with gravity and surface geology features on the island. This comparison indicates that the main rift zones of Mauna Loa and Kilauea are north‐dipping transcrustal fracture zones, closely related to fundamental processes of uplift and volcanism in the upper mantle. It is concluded that, although most of the island of Hawaii is subsiding, owing to the response of the crust to the load of the volcanos, the southeastern flank, which includes Kilauea volcano, is being inflated and uplifted by magmatic intrusions.

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