AbstractThree olivine dolentes D1, D2, and D3 form a multiple intrusion of Tertiary age. The earlier intrusions, D1 and D2, fill the conduit in the lower part of the hill. The final intrusion D3 broke through the solid plug of D1 and D2 along restricted channels to fill the conduit in the upper part of the hill. The intrusions are exposed at the present erosion level of the Upper Basalts and near the top of the original lava‐plateau. D1 contains layers full of cognate platy xenoliths; D3, at the south end of the hill, is crowded with cognate xenolithic sheets, and similar sheets settled on to the floor of the D3 intrusion elsewhere. The xenolithic sheets are considered to be surface crusts formed at the top of the magma column and carried to their present place by the circulatory system of a lava‐l