Scientific American magazine reported that if the entire Greenland ice sheet melted, global sea levels would rise by 24 feet. The article clarified by saying, “The sheet won’t melt all at once, of course…” What articles like this fail to convey is that Earth has experienced radical sea level changes throughout both geologic and human history.
Geologic history shows marine deposits in places you wouldn’t expect. When I taught earth science, I took my classes to Thornton Reef on the south edge of Chicago, Illinois. I am told that the gravel pit now occupying the reef is the largest in the United States. On one trip there, a student found the tube of a cephalopod, an ancient giant octopus-like creature. Clam shells, snail shells, and brachiopods filled buckets that my students took home. This reef is similar to modern ocean reefs, except it winds through the south side of Chicago with a major interstate highway running right through it.
Other examples of historic radical sea level changes are abundant. Oolitic limestone in southern Indiana consists of tiny ocean creatures called oolites. The limestone in the Grand Canyon contains marine deposits. On the other end of the scale, canyons are cut into continental shelves along the U.S. East Coast of the United States. Those canyons were cut when the shelf was out of water. Scuba divers have reported signs of ancient human-made structures and fire pits in those canyons.
Was the Red Sea at the same level when Moses led the Israelites across? Are people searching for Egyptian armor and chariot remains in the wrong spots? The “Sea of Reeds” was likely dry land at that time, so efforts there are probably doomed to fail. We still have much to learn about climate history, radical sea level changes, and ancient peoples. As our technology improves, discoveries will increase, and we look forward to uncovering more evidence of Earth’s history.
— John N. Clayton © 2025
Reference: “Greenland’s Frozen Secret” in the July/August 2025 issue of Scientific American, pages 26-36.
John Cooper explores dry land evidence for the credibility of the biblical account in a series of videos produced by Does God Exist?