Leftovers of Earth’s dramatic formation

Ultra-Low Velocity Zones sit between the Earth's outer core and lower mantle. Researchers have uncovered the most detail ever of the mysterious structures laying between the Earth's mantle and core, also providing the strongest evidence yet they started life as an ocean of molten magma that eventually sunk. The team of international researchers, including scientists from The Australian National University (ANU), used thousands of computer-modelled seismic waves to examine Ultra-Low Velocity Zones (ULVZs) beneath the Coral Sea between Australia and New Zealand. The area was selected because of the high frequency of earthquakes and the seismic waves these events unleash. ULVZs sit at the bottom of the planet's mantle and on top of its liquid metal outer core, and are so thin that they are normally invisible to tomographic imaging. For decades, scientists have speculated they are leftovers of the violent processes that shaped the early Earth. Study co-author, Professor Hrvoje Tkalcic from ANU, said the team's findings confirm the chemicals, rocks and layers that make up ULVZs have largely been sitting unchanged for billions of years and the early days of the planet's formation.