But the Bible says how much the floodwaters rose—the waters of Noah’s Flood continued to rise on the earth until “all the high mountains under the entire heavens were covered.” (Genesis 7:19)
“Oh,” the skeptic will say, “The people who wrote the Bible are only talking about their local area. They didn’t know about the rest of the world.”
Even if that were true, that they only knew about the Middle East, then what mountains would they have known about? Jerusalem rises 600 metres above sea level. If the mountains of Jerusalem were covered how much of the rest of the world would have been inundated?
You can check the levels for yourself these days using the Google mapplet at heywhatsthat.com. The above figure shows in red how much of Australia would have been covered if the waters had just risen enough to cover Jerusalem. There is very little of Australia still above sea level.
But the people who came off the Ark settled in the area around Babylon (Genesis 11:2). The Zagros Mountains to the north-west rise 2,000 to 4,000 metres above sea level (You can check using Google maps with the terrain view). At 2,000 metres virtually the whole of Australia would have been underwater.
Remember that the Flood lasted more than a year, and that, after it peaked, the water was going down for many months before those on the Ark saw any other mountains appear above the surface (Genesis 8:5).
When I hear someone say the Bible is only describing a local flood I wonder if they have read what the Bibles actually says about the Flood, or if they appreciate geography of the Middle East.
The mountains of Jerusalem and the Zagros Mountains did not exist before the Flood, but were pushed up toward the end of the Flood. I’m just using them for the sake of the local-flood argument.