How people groups got to other continents

Ps 104.6-9 describes a change in the relatively flat earth topography which God used to cause the global flood waters to recede and expose land. God caused the earth's crust to shift creating higher elevations of mountains and deeper basins in which the flood waters could accumulate to form the oceans. This global shifting of the tectonic plates of the earth's crust is likely what was meant in Gen 10.25 by the earth being divided. Before this continental shifting and ocean-forming was completed it apparently was possible for land travel from the Mesopotamia area of the Plain of Shinar (Gen 11.2) to other locations which, after the tectonic shifting and continent forming activity finished would have been over the whole earth, as described in Gen 11:8-9. This sequence would have enabled people groups to settle on the continents we now see as being impassibly separated by oceans.