Our planet's internal weakness
- Resource Type
- Authors
- James A. Van Orman
- Source
- Nature. 465:432-433
- Subject
- Core (optical fiber)
Orders of magnitude (entropy)
Physics
Multidisciplinary
Planet
Reflector (antenna)
Geophysics
Diffusion (business)
Anisotropy
Earth (classical element)
Perovskite (structure)
- Language
- ISSN
- 1476-4687
0028-0836
The influence of the region where the lower mantle meets the core extends to Earth's surface. A computational study of mineral properties shows one way forward in understanding this enigmatic zone. Michael Ammann and colleagues have applied first-principle methods to calculate absolute diffusion rates in the mineral post-perovskite in the conditions prevailing in the Earth's lower mantle. They find that the diffusion of Mg2+ and Si4+ in post-perovskite is extremely anisotropic, with almost eight orders of magnitude difference between the fast and slow directions. This could render post-perovskite up to four orders of magnitude weaker than perovskite, and could reconcile seismic observations of a D′′ reflector with recent experiments showing that the width of the perovskite to post-perovskite transition is too wide to cause sharp reflectors.