Entablature is probably the result of cooling caused by fresh lava being covered by water. The flood basalts probably damned rivers. The division of colonnade and entablature is the result of slow cooling from the base upward and rapid cooling from the top downward. 1931 postcard of Devils Tower, Wyoming, a shallow intrusion that formed columnar jointing as it cooled. Possible mechanism for the formation of columnar jointing at Devils Tower.
Isotherms are layers with the same temperature.
Joints formed perpendicular to the isotherms as the rock cooled. In 1916, Sosman proposed that the columns are the results of a system of hexagonal convection cells. Sosmans model was based on experiments of wax or oil in a flat dish. Critics noted that lava flows do not gain heat from their bases but actually lose heat from the top surface. Furthermore, the shape of the convection cells did not resemble hexagonal columns.