There are sinkholes on land and black holes in space. But did you know there are blue holes in the ocean? And scientists now know that blue holes hold clues about past weather conditions.

Blue holes are vast pits made of limestone or coral reef in the sea floor. Layers of sand at the very bottom show a record of hurricanes. Like rings of a tree can be counted to determine its age, blankets of silt in blue holes can be counted to number storms.

The catch is, you can’t just swim down for a quick look. Imagine you take a boat out to the Great Blue Hole off Belize. Scuba diving just below the surface is no problem. You’ll see corals, turtles, and sharks. But below about 300 feet, there’s little animal life to be found. It’s best to be in a submarine after that.

At that depth, a thick, toxic layer of hydrogen sulfide spreads over the entire width of the hole. There’s no oxygen below it. Nothing can survive. That’s good for the sandy layers, though. Creatures don’t disturb them. 

Natural currents fling small grains of sand into blue holes. Raging hurricanes throw larger grains. The careful eye can spot the different textures and layers. These natural records show that violent storms used to be a lot more common than they are now. 

Scientists made another discovery. At about 400 feet into the Great Blue Hole, small stalactites project downward. Stalactites are fingerlike formations. They occur when water drips down stone, leaving minuscule mineral deposits that build up over time.

The Great Blue Hole used to be a dry cave. Scientists suspect most blue holes are caves that formed during an Ice Age. When sea levels rose, the caves flooded and crumbled. They became blue hole storm trackers.

Why? God can use nature as a history book and a calendar. Look closely at trees, layers of soil, patterns of erosion. What stories does your own back yard have to tell?