Earthquakes are strong evidence that pieces of Earth shift around with respect to other pieces. In the 1950s and 60s, geoscientists examined many types of evidence as they tried to figure out a theory to systematically explain this mobility. We will examine some other types of evidence in class. One additional example is illustrated below. This map shows seafloor ages in color-coding.
Ages refer to the time when basaltic lava flowed from volcanoes to form the seafloor.
Usually, the basaltic crust is covered by younger sediments that rain down to the seafloor through the overlying water column. Cores can be drilled through the sediment cover to obtain samples of the underlying lava, which is then dated by chemical methods.