What did Harry Hess discover that helped Wegener prove the continental drift theory?

Harry Hess: The Guy Who Finally Made Continental Drift Make Sense

Back in the early 1900s, a fella named Alfred Wegener came up with this wild idea: the continents weren’t always where they are now. He figured they were all smooshed together way back when, in a supercontinent called Pangaea, before breaking apart and drifting off to their current spots. Sounds kinda crazy, right?

But Wegener had some pretty convincing evidence. I mean, look at a map – South America and Africa fit together like puzzle pieces! Plus, he found the same types of fossils on different continents, and mountain ranges that seemed to line up perfectly, even across oceans. For instance, you’ve got the Appalachians in North America, looking like they’re just begging to be reconnected with the Scottish Highlands. And the Glossopteris fern? Found it all over the place – South America, Africa, Australia, India… It was like the continents were shouting, “We used to be buddies!”

Still, nobody really bought it. Wegener’s biggest problem? He couldn’t explain how the continents moved. He thought they sort of “plowed” through the ocean floor, which, let’s be honest, sounds a bit ridiculous. Without a good explanation for the “how,” continental drift was pretty much dead in the water.

Then along came Harry Hess. A geologist and a Navy guy – talk about a cool combo! During World War II, he was a submarine commander, and he used sonar to map the ocean floor. And what he found was mind-blowing: huge underwater mountain ranges called mid-ocean ridges, and these super deep trenches.

Fast forward to the early 60s, and Hess drops this bombshell: seafloor spreading. Basically, he said that molten rock from inside the Earth oozes up along these mid-ocean ridges, creating new ocean floor. This new floor then slowly moves away from the ridges, like a giant conveyor belt. And guess what’s sitting on that conveyor belt? Yep, the continents! As the seafloor spreads, it carries the continents along for the ride. At the deep-sea trenches, the old seafloor gets pushed back down into the Earth, like some kind of giant recycling program.

Suddenly, everything clicked! Hess had finally figured out how the continents could move without having to plow through solid rock. His idea also explained a bunch of other weird stuff:

• Why the ocean floor is so young: Because it’s constantly being made and destroyed!
• What those mid-ocean ridges are: The places where new ocean floor is born.
• What those deep-sea trenches are: The graveyards where old ocean floor goes to die.
• Why volcanoes and earthquakes happen where they do: Because that’s where the Earth’s plates are bumping into each other.

Of course, scientists wanted more proof. And they found it by studying the magnetic field recorded in the rocks on the ocean floor. See, as the molten rock cools and hardens, it acts like a compass, recording the direction of Earth’s magnetic field at that time. And the Earth’s magnetic field flips every now and then – north becomes south, and vice versa. This creates a pattern of magnetic “stripes” on the ocean floor, like a barcode.

The cool thing is, these stripes are symmetrical on either side of the mid-ocean ridges. It’s like the Earth is saying, “Hey, look! New crust is being made here, and it’s moving away equally on both sides!”

Hess’s seafloor spreading, combined with the magnetic stripe evidence, led to the theory of plate tectonics. This theory says that the Earth’s surface is broken up into huge plates that are constantly moving and bumping into each other. And that’s what causes all the cool (and sometimes scary) stuff that happens on our planet: earthquakes, volcanoes, mountains… and, of course, continental drift.

So, hats off to Harry Hess! He took Wegener’s crazy idea and turned it into a cornerstone of modern geology. Without him, we’d still be scratching our heads, wondering how the heck the continents got to where they are today. He showed us that sometimes, the most important discoveries are hidden deep beneath the surface.