The theory must be consistent with these observations and new additional observations. Below are some observations about the features and characteristics of ocean basins and margins which must be adequately explained in any theory accounting for the dynamic nature of the Earth's crust. Many of these observations were made after World War II when geophysical exploration of the ocean exploded. The theory of plate tectonics was made possible by many of these observations, which provided new insights into Earth processes.
Ridges have very little sediment cover and is very young.
Sediment thickness increases away form the Mid-Atlantic Ridge and reaches maximum thickness along the adjacent continental margins. The oldest marine sediments in the Atlantic also occur along the margins of the basins. These structures were formed at sea level but now occur at depths deeper than any possible past lower sea level stand. Positive magnetic anomalies are places where the magnetic field is stronger than expected. Negative magnetic anomalies are magnetic anomalies that are weaker than expected.