Deep within the Earth, there’s a secret reservoir of water. Imagine a blue rock called ringwoodite, tucked away 700 kilometers below the surface in the mantle—the hot layer between the Earth’s crust and its core.
This discovery sheds light on where Earth’s water came from. Some scientists believed that comets brought water when they collided with our planet. But now, there’s another idea: the oceans slowly leaked out from within the early Earth itself.
Steven Jacobsen, a researcher from Northwestern University, explains, “It’s strong evidence that Earth’s water originated from within.” This hidden water might even play a role in keeping our surface oceans stable over millions of years. Jacobsen’s team used 2000 seismometers to study seismic waves caused by earthquakes. These waves travel through Earth’s interior, including the core, and can be detected at the surface. Think of it like the Earth ringing like a bell after an earthquake.
By measuring wave speeds at different depths, they figured out which types of rocks the waves passed through. The water layer revealed itself because the waves slowed down—they take longer to move through wet rock compared to dry rock.
Jacobsen even conducted experiments in his lab. He grew ringwoodite and subjected it to extreme pressures and temperatures, mimicking conditions 700 kilometers down. Sure enough, they found signs of wet ringwoodite in the transition zone, which separates the upper and lower parts of the mantle. It’s like the rock is sweating water along its grain boundaries.
Another scientist, Graham Pearson from the University of Alberta, studied a diamond from the same transition zone. That diamond had water-containing ringwoodite, providing strong evidence for water deep within the Earth. But here’s the twist: Jacobsen’s evidence only points to watery rock beneath the United States. Now he wonders if this reservoir wraps around the entire planet.
In the end, we should appreciate this hidden treasure. Without it, Earth’s surface would be very different—mountaintops might be the only land peeking out!
