After the flood, how did we get different races, and how did animals like kangaroos reach Australia?

Before the flood we believe there was one solid land mass called Pangaea. One way you can see this is by looking at South America: it fits right into Africa, like hand in glove. You can squeeze the other continents in and make a puzzle of one land mass, and the rest of the earth was water. Then at the flood, Genesis 7 says the land broke up, so there were fissures or cracks in the Pangaea land mass. The water from the ground, and there is a lot of it down there, about three times as much as is in the oceans, came up through those cracks and shot up into the atmosphere, and kept doing that for forty days. That is why it could rain for forty days: most of the water was coming from underneath the surface of the earth, not from the clouds. After a year the animals are let out of the ark, and Pangaea had cracked but had not spread very far, because there was not enough time. The momentum of a big continental mass moves it, but slowly, so there were still land bridges. The kangaroos went south, the bears went north, the lions stayed around the equator, and as the land masses continued with that momentum they separated all the more, until thousands of years later they are where they are now. As for the races: God built us so our physical constitution is adaptable to different climates. After the flood the average temperature probably dropped about ten to fifteen degrees and the pressure changed. Those adaptations happen fast, within a generation or two, and God built that into our DNA. If you live around the equator where the sun is strongest, your skin needs protection, so you have dark-skinned people there; in the north, Swedish people are blond and blue-eyed because they do not need that protection. We have had thousands of years since the flood, say around 2500 BC, for that variation, which also shortened lifespans: Shem died at 600, a couple generations later 400, then 200, Abraham at 175, and Joseph at 110, because the climate changed and was no longer the pristine pre-flood environment.