Space and Earth Sciences News

Using a diamond-anvil cell to recreate the high pressures deep within the earth, researchers at the California Institute of Technology (Caltech) have found unusual properties in an iron-rich magnesium- and iron-oxide mineral that may explain the existence of several ultra-low velocity zones (ULVZs) at the core?mantle boundary. A paper about their findings was published in a recent issue of Geophysical Research Letters (GRL).ULVZs?which were first discovered in the early 1990s by researchers at Caltech led by Donald V. Helmberger, Smits Family Professor of Geological and Planetary Sciences?are found in a patchwork distribution just above the core?mantle boundary, which is located at a depth of 2,900 kilometers. In the ULVZs, which range from a few kilometers to tens of kilometers in depth and are up to 100 kilometers across, the velocities of seismic waves slow down by up to 30 percent.Previously, geophysicists had suggested that the ULVZs might be composed of liquid-bearing, partially melted materials; in thi