Geodetic measurements in Fayal, Pico and San Jorge showed some horizontal expansion of these islands. The total expansion during the interval 1936-1979 amounts to· several metres, being considerably greater than the average sea floor spreading for that area of the Atlantic Ocean. This suggests that the spreading could be a discontinuous phenomenon, depending on short lived epochs of quick strain release. A vertical pulsation on the central part of Pico volcano was also detected; the pulsation has amplitude of about one metre and period close to one year. Its-seems due to periodic changes of pressure inside the magma chamber.