We report important new findings from 14 months of observations of ocean bottom pressure variations in the southeastern Pacific. One is a pressure increase starting in December 1997 at almost the same time as the termination of the 1997--98 El Ni¿o. It is also coincident with a remarkable change in the J2 term of the Earth's gravity field. These results suggest that the El Ni¿o might have brought about mass redistribution in the eastern Pacific Ocean. The other feature in the observations is a local pressure variation across the spreading axis of the ultra-fast spreading southern East Pacific Rise. It is estimated that the seafloor near the spreading axis was depressed at a rate of about 20 mm/month. The result suggests thermal contraction of the crust in the spreading center in the inter-eruption period.