The Gulf Coastal Plain is an area of active diastrophism. Five classes of evidence are discussed--earthquakes, fissures and faulting, regional warping, local subsidence and uplift, and pseudo-diastrophic features.

Although the Gulf Coast is described as an area of low seismicity, many earthquakes have occurred in the past and more should be expected in the future. Fissuring and faulting have been taking place in the Gulf Coast during historic time. The same statement is true for regional warping. Many cases of local subsidence have been recorded and in some localities subsidence and uplift are taking place to-day. Hoskins Mound salt dome is believed to have risen ½ foot in 23 years.

Much of the diastrophism occurring in the Gulf Coast is believed to be the result of the force of gravity. Two important factors influencing such diastrophism are, local inequalities in support and large local variations in density. Where such conditions and forces are present, compaction of the sediments by grain rearrangement often influences the form which results and may in some cases be a cause of diastrophism. Compaction may be aided by microseisms. The writer asks if the warping noted might be the result of waves in the earth's crust traveling at geologically slow speeds. The basin of the Gulf of Mexico is compared with a shallow rubber pan partly filled with stiff mud which is constantly being stretched, squeezed, and warped.

Many diastrophic features affect physiography and can be traced by use of aerial photographs even where they can not be followed on the ground. More publicity should be given to the subject of historic diastrophism to encourage individuals to make known their personal observations.