Ridge push results from the force exerted by gravity on the recently formed lithospheric rock near divergent plate boundaries. The lithosphere (crust) is being newly formed at these mid-oceanic ridges from the upwelling of magma from the mantle. Gravity pushes the cooled and hardened rock away from the ridge (downhill) and exerts a force on the entire plate that moves it towards a zone of subduction.
The difference in the coloration of the whale is due to mutation. Mutation is an alteration of the gene of an organism which can result in a change in phenotypic qualities. Mutation can be caused by exposure to mutagens such as industrial chemicals.
