Globigerina is a microscopic sea animal. It is something like
an amoeba in structure, yet it is protected by a shell. It lives in
myriads at the surface of the sea. At death the shell, which is as
small as the finest dust—so small that it cannot be seen without a
microscope —settles slowly to the bottom of the sea, where it forms deep
beds of ooze or fine mud. The chalk
cliffs of England and France consist largely of these shells. Enormous
thicknesses of rocks appear to be composed of similar oozes hardened by
heat and pressure. Geologists assert that if the world last long
enough, the deposits of this sediment, now collecting so slowly on the
floors of the oceans, may one day be hardened rock crumpled up into
mountain folds of new continents.
