For the seafloor spreading hypothesis to be accepted by people, Hess would need evidence to support it . First of all, the temperature underneath the Mid-Atlantic Ridge is warmer than lower, surrounding areas. This is
because magma is below it, which can come out of the center of the ridge because of mantle convection which would make new seafloor when it cooled. Seafloor drilling led to the
discovery that older rocks are farther away from the Mid-Atlantic Ridge and younger ones are closer. This means that the magma coming out of the ridge is pushing old seafloor away. Third, subduction gets rid of seafloor, but it is not slowly disappearing. The only explanation is seafloor spreading. Finally, magnetic polarity alternates between normal and reversed. Igneous rock make tiny crystals that show which one it was at the time. So, since there are stripes of igneous rock with alternating crystals, it means that the seafloor is slowly spreading.