Saturday, August 24, 2019

"Earth's inner core is doing something weird"

Okay, what is going on?
Last September it was:
"The Earth is wobbling more than it should, and humans are likely the cause" 
Quoting Grandmother: "If it's not one tham ding it's another."

Then in January:
"Earth’s magnetic pole is on the move, fast. And we don’t know why" 
As if there wasn't enough going on, what with the volcanoes and the locusts and....I suppose it's probably time to start scanning for 'frogs' and 'festering boils' in the various news feeds.

Now this, from National Geographic:

Data from old Soviet weapons tests are helping scientists get a high-resolution look inside our planet.
On September 27, 1971, a nuclear bomb exploded on Russia’s Novaya Zemlya islands. The powerful blast sent waves rippling so deep inside Earth they ricocheted off the inner core, pinging an array of hundreds of mechanical ears some 4,000 miles away in the Montana wilderness. Three years later, that array picked up a signal when a second bomb exploded at nearly the same spot.
This pair of nuclear explosions was part of hundreds of tests detonated during the throes of Cold War fervor. Now, the records of these wiggles are making waves among geologists: They have helped scientists calculate one of the most precise estimates yet of how fast the planet’s inner core is spinning.
Surface-dwellers know that Earth spins on its axis once about every 24 hours. But the inner core is a roughly moon-size ball of iron floating within an ocean of molten metal, which means it is free to turn independently from our planet’s large-scale spin, a phenomenon known as super-rotation. And how fast it’s going has been hotly debated.

Capitalizing on the zigzagged signals from those decades-old nuclear explosions, John Vidale, a seismologist at the University of Southern California, now has the latest estimate for this rate. In a recent study published in Geophysical Research Letters, he reports that the inner core likely inches along just faster than Earth’s surface. If his rate’s right, it means that if you stood on a spot at the Equator for one year, the part of the inner core that was previously beneath you would wind up under a spot 4.8 miles away.

“It’s a careful, good piece of work,” says Paul Richards, a seismologist at Columbia University who was a coauthor on a 1996 study that first documented super-rotation of the inner core. “Something is changing down there.”
Better understanding the history and current dynamics of the iron blob nestled within our planet could yield more clues to the processes charging and stabilizing our magnetic field—a geologic force field that protects our world from various kinds of harmful radiation. We don’t yet fully understand how this magnetic dynamo works, but scientists strongly suspect it’s tied to the mysterious motions deep inside the planet. (Learn what really happens when Earth's magnetic field flips.)

“The Earth is this extreme natural lab,” says Elizabeth Day, a deep-earth seismologist at Imperial College London who was not part of the work. Thousands of miles below our feet, pressures are crushing and temperatures are searing. “We can’t easily reproduce all of those in an actual laboratory. But if we can peer into the Earth, we get a bit of insight into this really extreme set of conditions.”...