New research led by Jo Stephenson at Australian National University in Canberra has revealed that there may be a hidden layer inside the Earth’s solid inner core. It is believed that it could have something to do with changes in the structure of iron under extreme temperature and pressure. The study shows that there may be more complexity to the inner core than previously thought.
The Earth’s core has two parts. The liquid outer core starts about 2,897 km from the surface of the Earth and is composed of liquid metals at temperatures of 2,204 to 4,982 degrees Celsius. At about 5,150 km below Earth’s surface, the core transitions to solid iron and a bit of nickel.
Because there is no way to get to the inner core, scientists use earthquake waves to make images of the core. Waves from an earthquake on one side of the planet that are detected on the other side of the planet exhibit subtle changes that scientists can use to recreate an image of what they’ve passed through.
For reasons unknown, when waves pass through the core from north to south, they travel faster than waves passing through the core parallel to the Earth’s equator. The technical term for this oddity is anisotropy. At the very center of the inner core, these waves behave differently and the anisotropy seems not to match that of the rest of the inner core.
Stephenson created a dataset of about 100,000 earthquake waves that passed through this region of the core and applied an algorithm to it. They found an inner-inner core, starting from about 650 km from the center of the Earth.
The core is important to understand, said Stephenson, because its swirling interactions create Earth’s magnetic field. The magnetic field shields the planet from charged particles streaming from the sun which is critical to life.
Pappas, S. (2021, March 8). Earth has a hidden layer, and no one knows exactly what it is. Live Science. https://www.livescience.com/new-earth-layer-solid-inner-core.html