Did the continents divide before or after Noah's flood?
The Bible seems to indicate that for a period of time after the flood of Noah the earth's continents were all connected. They became disconnected, however, during the days of Peleg. Genesis 10:25 states the following.
"To Eber were born two sons: the name of one was Peleg, for in his days the earth was divided . . ."
Peleg was born 101 years after the flood ended. Some believe that the division caused during the days of Peleg refers to the division of earth via plate tectonics or that put simply that the continents separated. This supposition is incorrect. If massive plate movements during the time of Babel or Peleg had divided the earth it would have caused catastrophic rearrangements of the earth. This would have been recorded in various historical accounts. The fact that this division is of a less catastrophic nature weighs against plate tectonics being the cause of this division.
The connection of the continents allowed animals to move into areas that were later separated by water. For example, animals and people moved into Australia, Micronesia, Polynesia and also other places such as North and South America via the land bridge that once connected present day Russia and Alaska.
Genesis 10:25 reveals that the earth and its land masses were divided by rising sea levels. The name of Peleg is derived from the word pelagic. This word means 'watercourse' in the Hebrew and 'division' in the Aramaic. It also means relating to, or living or occurring in the open sea, oceanic. This word is often used as a descriptive term. We often speak of pelagic birds, which means marine or ocean birds. The word Peleg, in its basic use, means division by water, as in Job 38:25 where it states "Who has divided (peleg) a channel for the overflowing water . . ."
The Genesis flood caused the ice age. This would lock up massive amounts of water in polar ice. As the earth warmed up and the polar ice melted it would have caused a corresponding rise in the level of the earth's oceans. As the ocean levels rose the rising waters would have separated various landmasses. This would have included the separation of Western Asia (Russia) from Alaska via the Bering land bridge. Other areas separated would have included Australia, New Zealand, and Southern Asia. If the waters had raised slightly more the Isthmus of Panama would be underwater today, which would have separated North and South America.
Shortly after the flood the earth began to thermally stabilize and the polar ice began to melt. This was one of the reasons that God was adamant that human migrations take place quickly (Genesis 9:1,11:1 - 9). As the ice began to melt, routes that were easy to traverse (for animals and humans) would have been inundated by rising water. This is one of the reasons that God confounded the languages at the tower of Babel. The new languages caused the people to migrate immediately before many of the migration routes, especially between continents, would be sealed off by rising water. The change in the earth's climate, however, meant lifespans significantly decreased after Noah's flood.