The three dimensional seismic velocity structure from the surface of the Earth to a depth of about 900 km was determined from fundamental and higher mode surface waves. Velocity anomalies near the surface correlate well with the age of the surface rocks. Reconstruction of the ancient continent Pangea connects all fast velocity anomalies near the center of Pangea. Fast velocity anomalies extend to 200--400 km. Considering the resolving power of long period surface waves, this indicates that Pangea was a continent with a lithospheric thickness of about 200 (¿100) km or larger, which broke up right in the middle (Central Atlantic). Examinations of seismic velocity sections with respect to depth show different depth penetration of fast velociy anomalies under various continents such as North America, South America, Eurasia and Africa. We speculate that continents possessed different thicknesses before Pangea was formed and had moved over the surface of the Earth independently. ¿ American Geophysical Union 1987